Conference Agenda

Compute energy-delay performance is today communication limited. The scaling vectors of cost, bandwidth density and energy are challenged by the physical limits of electronic interconnect bandwidth. The emergence of foundry compatible silicon photonics solutions promises to relieve this roadblock with electronic-photonic integration at the package level. These solutions, as described in the recent release of the 2023 Integrated Photonics System Roadmap – International, will be review with a focus on materials, tools and processes for sustainable system performance scaling.

Silicon photonics subwavelength metamaterials have found use in of applications ranging from optical communications to sensing. In this invited talk, we review some of the latest advances in the field.

Photonic integrated biosensors have garnered considerable attention due to their promising applications in various fields such as healthcare. Differentiating specific targets from interfering background effects is a challenging task. In this work, a dual-polarization Mach-Zehnder interferometer (MZI) with coherent phase readout is proposed to identify refractive index changes from different layers above the waveguide surface, thus improving sensor specificity. All the system building blocks have been designed for a 300 nm-thick silicon nitride platform, fabricated and characterized. The first experimental results show a bulk waveguide sensitivity of 0.17 RIU/RIU for TE polarization and 0.25 RIU/RIU for TM, confirming the correct functioning of the sensors when operating for each polarization separately. Future work will focus on simultaneous sensing with both polarizations and experiments with layered variation of refractive indices.

Laser direct writing (LDW) systems offer remarkable opportunities to sculpt materials at the micro and nanoscale. However, traditional LDW methods are limited in throughput because of their inherent serial nature– material modification occurs point-by-point. Here we propose a paradigm shift for LDW systems, from point-by-point to region-by-region operations. Our approach leverages ultrasonic waves to shape the laser radiation. Piezoelectric actuators, immersed in water, generate acoustic and, thus, density or refractive index waves, stationary in space and oscillating (MHz) in time. A laser beam traveling through such an acoustically controlled medium gets diffracted and forms interference patterns as well as multiple shape-tailored laser beamlets. Synchronization of the arrival of laser pulses with respect to the refractive index oscillation enables the selection of different inference patterns or beamlet configurations at the unsurpassed speed of MHz. Our system is simple and can be easily integrated into traditional LDW systems. This allowed us preparing micro and nanostructures over a large area (~cm2) of a sample in either additive or substrative mode. We validated our idea by preparing and stitching together, while scanning a sample surface with user-selectable laser patterns, pixels with different either nanostructured colorations or wettability.

MoO3 is extensively studied in the mid infrared range due to the strong anisotropy of its optical properties. We investigate the mid-infrared thermo-optical properties of polycrystalline alpha-phase Molybdenum trioxide (-MoO3) thin films grown onto SiO2 substrates in the temperature range 20°C-250°C reporting a thermo-optic coefficient of the mean order of 10-4 K-1.

Significant advances in mid-infrared optical technology depend on the development of innovative materials blending the properties of metals and insulators. In our work, we have systematically explored the thermochromic phase transition of vanadium dioxide. By introducing tungsten doping at room temperature through pulsed laser deposition technique onto sapphire substrates, we were able to precisely tailor the material's infrared optical responses. Our control over the tungsten concentration enabled us to finely tune both the amplitude and frequency of optical phonon resonances, as well as the free-electron response.

Molybdenum disulphide (MoS2) and is a transition metal-dichalcogenides (TMD) material has layered structure. Recently it has drawn significant attention for exploring optoelectronic and photonic properties at sub-nanometre scale. The TMDs possess direct bandgap which is quite attractive for device engineering and applications in photovoltaic, energy storage, and bandgap engineered light-sources. We have synthesized 2H MoS2 using hydrothermal synthesis at 240 ⁰C for 24 h. The as synthesized powder was used for the fabrication of MoS2 thin films using femto-second pulsed laser deposition (fs-PLD). The deposited films are stoichiometrically congruent with that of synthesized material. The materials were characterised using XRD, UV-vis absorption spectroscopy and Raman spectroscopy. Figure 1 below shows the Raman spectra of MoS2 films grown at different temperatures (400 ⁰C and 600 ⁰C). Shift in the Raman bands are seen for the films deposited at different temperatures. The structural and optical properties of deposited films were analysed and compared. Such a comparative analysis may offer materials fabrication platform in future for engineering optoelectronic and photonic devices on silica glass and silicon platforms.

Terahertz (THz) time-domain spectroscopic ellipsometry (TDSE) is a powerful, self-reference, and non-destructive technique for characterizing the electrical and optical properties of a wide range of materials including semiconductors such as doped silicon wafers. By analysing the polarization changes of THz pulses reflected off the silicon samples, TDSE provides detailed information on carrier concentration, mobility, complex conductivity, and complex dielectric response. This method leverages the unique sensitivity of THz radiation to free carrier dynamics in semiconductors, enabling precise measurements of doping levels, conductivity, and hence resistivity at once. The study demonstrates the capability of THz TDSE in distinguishing between different doping types (n-type and p-type) and concentration level, providing critical insights for semiconductor research and fast quality control in silicon wafer production.

The observation of organelles dynamics and macromolecular complex interactions inside living cells and tissues requires minimally invasive imaging strategies. In this context, photocontrollable fluorescent proteins (FPs) play a crucial role as tags in optical super-resolution microscopy and functional live cell imaging. To this end we have previously shown that reversibly switchable FPs enable fast (1 Hz for a 50 x 50 µm2) and gentler (< 1 kW/cm2 illuminations) nanoscopy (Masullo et al Nat. Comm 2018). Additionally, irreversibly photoconvertible FPs can achieve photolabeling with high spatiotemporal precision. Nevertheless, their photophysical complexity poses challenges in expanding such techniques toward multiplexing and in vivo imaging. Here, we explore novel photoswitching mechanisms for fluorescent proteins in the red and near-infrared region of the spectra and assess their compatibility with live cell imaging at the nanoscale (Pennacchietti et al, Nat. Meth, 2018). Finally, we present strategies to combine the spectral and photophysical fingerprint of distinct photocontrollable FPs to achieve multiplexing in live cell imaging at the nanoscale and photolabeling studies (Pennacchietti et al, Nat Comm, 2023).

Image Scanning Microscopy (ISM) enables good signal-to-noise ratio (SNR), super-resolution and high information content imaging by leveraging array detection in a laser-scanning architecture. However, the SNR is still limited by the size of the detector, which is conventionally small to avoid collecting out-of-focus light. Nonetheless, the ISM dataset inherently contains the axial information of the fluorescence emitters. We leverage this knowledge to achieve computational optical sectioning without sacrificing the conventional benefits of ISM. We invert the physical model to fuse the raw dataset into a single image with improved sampling, SNR, lateral resolution, and optical sectioning. We provide a complete theoretical framework and validate our approach with experimental images of biological samples acquired with a custom setup equipped with a single photon avalanche diode (SPAD) array detector. Furthermore, we generalize our method to other imaging techniques, such as multi-photon excitation fluorescence microscopy and fluoresce lifetime imaging. To enable this latter, we take advantage of the single-photon timing ability of SPAD arrays, accessing additional sample information. Our method outperforms conventional reconstruction techniques and opens new perspectives for exploring the unique spatio-temporal information provided by SPAD array detectors.

Simultaneous field- and aperture-plane (back-focal plane, BFP) imaging enriches the infor-mation content of fluorescence microscopy. In addition to the usual density and concentration maps of sample-plane images, BFP images provide information on the surface proximity and orientation of molecu-lar fluorophores. They also give access to the refractive index of the fluorophore-embedding medium. However, in the high-NA, wide-field detection geometry commonly used in single-molecule localisation microscopies, such measurements are averaged over all fluorophores present in the objective’s field of view, thus limiting spatial resolution and specificity. We here solve this problem and demonstrate how an oblique, variable-angle, coherent ring illumination can be used to generate a Bessel beam that - for supercritical exci-tation angles - produces an evanescent needle of light. Scanning the sample through the this evanescent needle enables us to acquire combined sample-plane and BFP images with sub-diffraction resolution and axial localisation precision. Background, resolution and polarisation considerations will be discussed.

We present the use of wavefront coding (WFC) combined with machine learning in a light sheet fluorescence microscopy (LSFM) system. We visualize the 3D dynamics of sperm flagellar motion at an imaging speed up to 80 volumes per second, which is faster than twice volumetric video rate. By using the WFC technique we achieve to extend the depth of field of the collection objective with high numerical aperture (NA=1) from 2.6 μm to 50 μm, i. e., more than one order of magnitude. To improve the quality of the final images, we applied a machine learning-based algorithm to the acquired sperm raw images and to the point spread function (PSF) of the generated cubic phase masks previous to the deconvolution process.

The ability to generate a structured illumination pattern in microscopy is a fundamental need of numerous optical microscopy techniques, such as Structured Illumination Microscopy (SIM) and HiLo microscopy. However, existing pattern generating techniques, such as using diffraction gratings or SLMs, are either slow, bulky, or very alignment-sensitive, making the widespread acquisition of such techniques harder. We present an integrated, monolithic device, fabricated in a glass substrate via Femtosecond Laser Micromachining, capable of generating and translating a highly stable structured pattern on top of the sample plane of a microscope, enabling a widefield microscope to perform SIM.

Specific surface artifacts and manufacturing errors on aspheric lenses can be interpreted in different ways based on the used metrology system. We will study one example that shows ambiguity between form error and inner centration. The investigation includes common tolerancing methods in optical design and how they can cover the observed artifacts, as well as the effects the artifacts have on optical performance.

A noval concept for ccp polishing calles pp (pea puffer) of small diameter aspheres, typically << 5 mm, enables the generation of aspheres featuring shallow radii of curvatures while requiring clear apertures that are too small for most ccp polishing method's footprint diameters. The pea puffer concept enables a high quality and low cost manufacture of small aspheres in industry.

We introduce an optimization framework for ray and wave optical tomographic volumetric additive manufacturing (TVAM).

In TVAM, tomographic patterns are projected with a light modulator onto a photocurable resin from different angular directions.

Once an energy dose threshold is crossed, the resin starts polymerizing.

Current approaches assume a ray optical model for light propagation, using the Radon transform as backbone, which breaks down for small features in the region of \SI{20}{\micro\meter}.

In this work we describe how a wave optical framework allows to optically print smaller feature sizes.

The optimization framework is written in the programming language Julia and allows for high-performance optimization of ray or wave optical based patterns for volumetric additive manufacturing.

This study provides a comprehensive overview of the investigation into reducing wafer deformation during laser polishing of fused silica. The study focuses on the Twyman effect, which causes unwanted curvature in thin plates subjected to surface treatment. Through careful analysis and experimentation, a strategy for minimising stress-induced deformation is proposed.

Photopolymerization is a light-based additive manufacturing (AM) technique that facilitates the fabrication of complex three-dimensional (3D) structures quickly and cost-effectively. One-photon polymerization allows printing with high speed despite its limited resolution. In contrast, two-photon polymerization (2PP) offers high precision and resolution but requires longer printing times. We propose a method combining 2PP and one-photon absorption (1PA) to get advantages of the dual capabilities, allowing for faster printing while preserving high resolution and enhancing depth sectioning. In this study, we employ a blue light to pre-excite a photocurable resin for rapidly reaching the polymerization threshold by 1PA and a precisely focused femtosecond beam to provide the missing energy for surpassing the threshold and solidifying the resin through two-photon absorption. First, we investigate the impact of the pre-sensitization by a blue light illumination on 2PP, demonstrating two orders of magnitude reduction in light dose. After that, we introduce a custom 3D printer utilizing blue light sensitization in a light-sheet mode on 2PP, which accelerates polymerization onset and improves surface quality.

We propose a new spatial light modulator (SLM) concept, relying on a local thermal modification of a thick liquid crystal layer, that is optically-induced through the absorption of a control beam. This innovative thermo-optically addressed SLM, coined TOA-SLM, has shown dynamic phase control capabilities over multi-octave light spectrum, as a promising candidate for spatial or temporal manipulation of ultrafast pulses. In addition to being ultra-broadband and programmable, such a device is low-cost, large-aperture and un-segmented with a high number of control points. The construction and training of a neural network-based statistical model provides configurable design of a prototype TOA-SLM. This step, together with the ultra-broadband acceptance of the device and its ability to introduce continuous and deep phase modulation over a large aperture, opens the way for ultrafast laser aberration compensation using this new technology.

We present results that show the possibility to arbitrarily shape the

driving laser for high-order harmonic generation with a spatial light modulator

in order to control different parameters of the generated harmonics

Dark optical solitons are solutions to the nonlinear Schrödinger equation in normal dispersion media with positive Kerr nonlinearity, exhibiting a discrete π phase jump. These solitons are valuable to applications within telecommunication. Recent advancements have demonstrated the generation of two-colour bright-dark soliton pairs through cross-amplitude modulation in laser cavities, resulting in mode locking. In this study we present for the first time full field characterization of the electric field of a dark pulse. We achieved this by performing Blind Frequency Resolved Optical Gating measurements using the synchronous bright pulse as the gate pulse. The retrieved dark pulse verifies the existence of the expected π phase jump in the phase of the dark pulse, confirming theoretical predictions.

This work presents a universal seeder architecture based on filamentation and parametric amplification from an Ytterbium pump laser for the generation of pulses with versatile properties in terms of central wavelength, bandwidth, CEP, and contrast for seeding high power amplifiers based on various technologies.

We present a general temporal shaping method based on spectral phase-only modulation for ultrafast laser sources. We explain the working principle of this technique and use it experimentally to generate a rampshaped pulse at the output of a laser source delivering 30 μJ 200 fs pulses at 500 kHz. This pulse is then launched inside a multipass cell to demonstrate non-linear wavelength shifting. A spectral tunability of 11 nm around the center wavelength of 1030 nm is achieved.

We will present how widely used techniques such as autoencoders can be used to perform phase noise characterization of optical frequency combs. Optical frequency comb is an optical source that produces evenly spaced frequency lines. It is considered as a frequency ruler and has diverse applications in: frequency referencing, grid synchronization, optical communication, calibration for spectrographs e.g.

Classifying chestnuts as healthy or diseased remains a complex challenge in quality assessment. In our study, we use THz imaging to determine accurately the health status of chestnuts. Through innovative spectroscopic analysis, we explore the potential of three distinct unsupervised data analysis techniques: Principal Component Analysis (PCA), k-Means Clustering, and Agglomerative Clustering. Compared to traditional analysis methods, our findings unveil the remarkable ability of these methods to differentiate between healthy, diseased and in an intermediate state chestnuts, even when concealed beneath the peel. This research not only advances our understanding of quality control in chestnut production but also highlights the potential of THz imaging in agricultural applications.

Deep neural networks based on physics-driven learning make it possible to train neural networks with a reduced data set and also have the potential to transfer part of the numerical computations to optical processing. The aim of this work is to develop the first deep holographic microscope device incorporating a hybrid neural network based on the plane-wave angular spectrum method for dynamic image autofocusing in microscopy applications.

Photonic Stochastic Emergent Learning (PSEL) represents an innovative paradigm rooted in mathematical brain modelling and emergent memories. In this study, we explore the intersection of these concepts to address memory storage and classification tasks. Leveraging optical computing principles and random projections, PSEL constructs memory representations from the inherent randomness in nature. Specifically, we select a set of highly similar random states generated by coherent light scattered from a diffusive medium. Classification is performed by organizing the memories spatially into different classes and comparing inputs to those stored memories. The results demonstrate the efficacy of PSEL in memory construction and parallel classification, emphasizing its potential applications in high-performance computing and artificial intelligence systems.

Exploiting nonclassical states of light allows new imaging and sensing approaches. In particular, nonlinear interferometers enable quantum imaging with undetected light. Here, based on the effect of induced coherence, samples can be probed with light that is not detected at all. Instead, its quantum-correlated partner light is recorded and yields the information of the sample, although it never interacted with it. This enables new sensing modalities beyond classical limitations. The talk will outline the fundamental concept, recent progress, limits, and perspectives for biomedical applications of nonlinear interferometers.

We present the Hartmann sensor's capacity, which is traditionally used for wavefront sensing, to measure the coherence properties of the signal. By reinterpreting the detection theory of the conventional Hartmann sensor within the framework of quantum tomography, we unveil the ability to quantify the mutual intensity function in the form of coherence matrix analogue to the density matrix of the mixed quantum state. With this analogy, we can use the quantum-inspired algorithms to reconstruct this matrix from experimental data.

Fast and accurate asphere and freeform measurements are in high demand by the optics manufacturing industry. Interferometric methods such as tilted-wave interferometry meet these demands but require accurate surface positioning of the specimen along the optical axis, since such measurements are sensitive to such positioning errors. In this work the Cat's Eye position will be investigated in terms of accuracy and repeatability as a reference position for surface positioning in tilted-wave interferometry. For this purpose, a two-regime method for specimen alignment using different optimization criteria is investigated and its repeatability is evaluated. Accurate and reproducible positioning into the Cat's Eye position together with interferometric movement tracking will allow accurate specimen positioning along the optical axis, which will significantly reduce the surface measurement errors associated with such misalignment and improve the overall measurement uncertainty.

Shack-Hartmann wavefront sensor is applied today in broad areas of interest. Especially in optical systems quality assessment, the SHWS provides fast and accurate wavefront measurement. The sensitivity, i.e., the minimal measurable change in the wavefront, is usually omitted when it comes to a single Zernike Polynomials level. There is no ISO standard either. Comparing the specifications of SHWS among different manufacturers, one can feel confused. Here, we show the sensitivity for single Zernike polynomials up to the third radial order. In addition, we calculate the minimal wavefront RMS at the quantum limit using Fisher Information theory and compare it with the standard modal reconstruction algorithm used in SHWS.

The analysis carries two regimes: weak signal for adaptive optics and strong signal for optical metrology.

In this presentation, we propose a measurement system to observe 2-D in-plane displacement at a fast sampling rate of 5 kHz using a sinusoidal phase modulation interferometer (SPMI). The SPMI consists of a Michelson interferometer incorporating an electric-optic modulator (EOM) with a modulation frequency of 5 kHz and a high-speed camera (HSC) synchronised to a clock signal at a frequency of 60 kHz, 12 times the modulation frequency. Phase demodulation of each pixel in the camera is performed by acquiring the light intensity signal to that pixel in synchronisation with the sampling signal and performing a specific addition or subtraction of them. By applying this procedure to all pixels in the camera, the 2D in-plane displacement can be obtained. This technique has the potential to measure fast, dynamic deformation of object surfaces and dynamic wavefront aberrations due to air fluctuations.

Due to the increasing demand of cooling systems, new techniques to produce materials with specific optical properties are being developed for innovative applications such as passive daytime radiative cooling (PDRC). In recent years, electrospun polymeric coatings have been proposed as one of the most promising and scalable techniques for PDRC, due to the high solar reflectivity induced by their nanofibrous structure. Specifically, electrospun poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) exhibit negligible absorption in the solar wavelength range, and a selective emissivity in the atmospheric transparency range provided by its C-F bonds. However, the production of these coatings by electrospinning involves the use of toxic or hazardous solvents. In this study, we explore the substitution of traditional solvents with a non-toxic one, i.e., dimethyl sulfoxide (DMSO), to produce PVDF-HFP electrospun coatings. Through an easy one-step electrospinning process, 35 μm-thick coatings composed of well-defined, cylindrical, uniform, and continuous fibers are obtained with comparable properties to those obtained using traditional solvents.

Radiative transfer dominated by scattering is paramount in a wide variety of fields, especially in passive cooling highly depending on light scattering of particulate media composed of polydisperse particles. However, the accuracy and efficiency of light propagation simulations in real particulate media are still limited by the huge computational burden and complex interactions between dense and polydisperse particles. Here, we proposed a new optimization strategy that can effectively and accurately predict optical properties of particulate media based on Monte Carlo simulation with particle size and dependent scattering corrections. In particular, we optimize the Monte Carlo method by considering dependent scattering effect (incorporating far-field and near-field effect in scattering parameter) and size distribution effect through the monosized particulate medium approximation. Both the scattering parameters and the experimental reflectance spectrum are fully examined, demonstrating our optimization strategy is able to simulate the photon motions in particulate media more accurately than existing conventional models. Furthermore, using the weighted solar reflectance as representative optical property, both numerical simulations and experiments confirm the superiority and universality of proposed optimization framework in a variety of materials systems.

Year by year, thermal shielding has seen an increase in importance for reduction of energetic consumption in vehicles and buildings as a passive method of cooling opposed to traditional antiecologic air conditioning. In this work, we report on the design and fabrication of flexible, multilayer polymer photonic crystals films, namely aegises. Exploiting their peculiar optical properties, aegises are designed to act as selective reflectors for the near-infrared radiation, principal cause of radiative heating by sunlight, while keeping a relative transparency in the visible range. Different polymers are used as alternating building blocks, and the efficiency of the fabricated structures is assessed via thermal experiments, achieving efficiencies greater than 25% in heating reduction.

A set of new nanohybrid polymeric formulations containing silicon compounds (like T8 silsesquioxanes or SiC nanoparticles) and small organic molecules (like azulene) have been deposited on adhesive aluminium tape, characterized and exposed to the outdoor environment of Casaccia (Rome), monitoring their temperature. Results of the first month of external campaign show that they exhibit PDRC effects.

Passive radiative cooling materials recently emerged as environmentally friendly technologies able to mitigate both the effects and the causes of global warming. Due to their tailored emissivity they can provide net cooling power without any external energy source thanks to their ability to dissipate heat from Earth into outer space (3K) at wavelengths between 8 and 13 μm, where the atmosphere is largely transparent in case of a cloudless sky. Among their many applications, these materials hold great promise for the thermal management of photovoltaic modules, where they could be used to lower their working temperature while selectively rejecting solar radiation below the band gap. In this study, we propose an optimised polymer pattern coating for the efficient shedding of heat from solar cells.

The emergence of ultrashort optical vortex pulses with spatiotemporal orbital angular momentum (OAM), has sparked a wide array of applications. Here, we provide a vortex retarder-based approach to generate few optical cycles light pulses carrying OAM from a Yb:KGW oscillator pumping a noncollinear optical parametric amplifier generating sub-10 fs linearly polarized light pulses in the near-infrared spectral range (central wavelength 850 nm). We characterize such vortices both spatially and temporally by using astigmatic imaging technique and second harmonic generation-based frequency-resolved optical gating, respectively. The generation of optical vortices is analyzed, and its structure reconstructed by estimating the spatio-spectral field and Fourier transforming it into the temporal domain. As a proof of concept, we show that we can generate sub-20 fs light pulses carrying OAM and with arbitrary polarization on the first-order Poincaré sphere.

We demonstrate a comparative study on single-mode fluoride fibers for mid-IR generation. We took into consideration examples of ZBLAN fibers from all leading manufacturers. The fluoride fibers were pumped with the 30-fs pulses from a Cr:ZnS oscillator which allowed for Raman soliton generation up to 4 μm and supercontinuum generation up to 5.3 μm.

Nonlinear pulse shaping based on Mamyshev regenerator is a powerful approach for ultrashort pulse generation. The performance strongly depends on the initial seed parameters. We investigate and design a nonlinear pulse shaper seeded by a long pulsed gain-switched laser diode for generation of high quality ultrashort pulses with flexible repetition rate. The shaper architecture provides more flexibility on the input diode requirements and can yield shorter pulses with the improved laser relative intensity noise. The system optimization is based on numerical simulations mapping the favourable parameters at each stage of the system and enabling identification of limiting factors.

We present a widely tunable laser source with narrowed linewidths at the level of 0.4 – 1.1 nm. The laser source incorporates a comb-profile fiber (CPF) which allows for spectral compression of the tunable optical pulses to the linewidths below 1 nm. The spectral compression factor is as high as 37.2 and is the highest obtained for this wavelength range. With the use of an electro-optic modulator (EOM), the laser system ensures rapid tuning up to 10 GHz. Together with the wide spectral range of 1600-1900 nm, and compressed spectral width, the source meets the requirements of the optical coherence tomography (OCT).

Due to the increasing demands and complexity of optical glass components to be processed in the future, advanced technologies and precision machining methods will be required in order to produce high-quality optics economically. The polyjet process enables the production of 3D printed gradient index (GRIN) polishing tools with hardness gradients by combining different polymer materials for e.g. synchrospeed polishing. In terms of their geometric design, these tools are significantly more flexible than conventional ones, where the polishing cloth must be glued to metal tool holders. The composition of the polishing pad material directly influences the process efficiency and quality at which the glass is polished. In a laboratory test the influence of the mechanical properties of the multi-material pads on process efficiency, i.e. their long-term stability and the polishing rate of the glass workpiece is demonstrated.

To prevent the disposal of minimally damaged lenses that fall outside the acceptable scratch and dig tolerance levels, an experimental study was conducted to repair mechanical scratches on a fused silica surface. The scratches were created using a diamond tip and then repaired using a CO2 laser. Various loads on the diamond tip and laser output power were tested. The transmission changes and subsurface damages were analysed. The surface quality analysis was performed using a white light interferometer, while the subsurface damage analysis will be performed using optical coherence tomography. Local absorption differences can be quantified using photothermal deflection. To significantly enhance local transmittance, brittle and ductile scratches of various depths have been successfully healed.

Mechanical chemical glass polishing is a complex process with mechanical and chemical interactions. While we have used Acoustic Emissions (AEs) already for basic measurements, we have researched the process and its parameters e.g., the density of the polishing slurry or the glass type for further investigation. We also have carried out crack tests on samples to investigate the crack mechanism.

We suggest the further investigation of AEs to improve the above mentioned process and to prepare a transfer of this approach for further processes.

Molecularly imprinted polymers are synthetic receptors that are replacing conventional bioreceptors because of their high selectivity, structural stability, lower cost, and ability to imprint wide range of analytes. Porous silicon based transducing systems are gaining popularity because of their, large surface area, lower cost, rigidity, and chemically active surface that can be modified easily. But integration of highly selective receptors on porous silicon substrates is crucial for development of highly efficient sensors. In this work we have integrated molecularly imprinted polymer on nanoporous silicon for label free sensing of quercetin which is among most important bioflavonoid in human diet. Vapour phase polymerization was utilized for polymerization inside the nanopores using pyrrole vapours and then template was removed to generate binding cavities. The sensor exhibited good sensitivity towards quercetin in liquid samples within concentration range of 0.5 to 100 µM with a remarkably high selectivity against competitive molecules. Finally, the sensor was examined for detection of quercetin in commercially available wine samples satisfactory results were obtained. Moreover, the sensor exhibited magnificent stability and reusability that makes it prominent for label free sensing of quercetin.

The crossed arrangement of excitation and collection optics is the defining feature of selective plane illumination microscopes. It results in an axial sectioning given by the thickness of the light sheet, whereas the lateral resolution depends on the numerical aperture of the collection optics. One disadvantage of this optical scheme is that it has been difficult to image large fields-of-view at high spatial resolution. Yet, it is often not necessary to image the entire sample at high resolution. Instead, a zoom from mm-scale over-views to regions-of-interest that are imaged at µm is often sufficient, e.g., for studying neuronal networks that simultaneously comprise cm-long connections and tiny (sub-µm) synaptic contacts, spanning 6 orders of magnitude. Observations over such different spatial scales typically require the use of different instruments. We here describe our ongoing efforts to build and characterise a compact light-sheet module designed for correlative micro- meso- and macroscopic imaging. Its particularity is that moves with the sample between micro- and macroscopic imaging arms. Based on a compact illuminator and flexible sample carrier the module is mounted on a motorised long-range, high-precision microscope table. The ability to perform seamless back-and-forth multi-scale imaging comes from a strict registering of image coordinates

Optical tweezers (OT) are an emerging tool for investigating the biological world at the single-molecule level. In particular, single-molecule force spectroscopy measurements with OT offer valuable information on the elastic and energetic properties of a molecule, allowing to achieve a complete characterization of its free energy landscape. In this work, we present the study of a DNA-based biosensor and the consensus RNA sequence of thymidylate synthase, which have been investigated by means of pulling experiments with OT.

Light-based 3D printing shows potential for biomedical applications by providing high-resolution features. Nevertheless, its effectiveness in printing through biological tissues is greatly limited by the optical opacity of the tissue. The poor tissue-penetration depth of ultra-violet (UV) or blue light, which is commonly used to trigger photopolymerization, further limits the in vivo applications of light-based additive manufacturing. Here, we introduce a novel additive manufacturing method through highly scattering media, employing upconversion nanoparticles (UCNPs) and the wavefront shaping technique. This method utilizes near-infrared (NIR) light for photopolymerization through scattering media, leveraging UCNPs both as a UV light source and a guide for wavefront shaping. Through harnessing the optical nonlinearity of upconverted fluorescence and memory effect correlations, we have successfully demonstrated high-resolution printing capabilities through a highly scattering layer, even when the signal is not localized.

Localized surface plasmon resonance (LSPR) sensing has already demonstrated its feasibility in biomedical applications. LSPR leverages the use of nanoparticles whose plasmonic properties can be explored using optical techniques. In this work, the plasmonic properties of silver nanoparticles were leveraged to try and explore their usefulness in biosensing. The nanoparticles were bound on trenbolone acetate which is an androgen anabolic steroid often abused by athletes in doping due to their ability to improve the athlete's aerobic capabilities, including building their muscle mass. The plasmonic properties of the nanoparticles bound on the target analyte were explored using NIR/UV-VIS spectroscopy. The results showed that the binding behavior could be monitored by assessing shifts in the silver plasmon band. The change in the band position was also assessed relative to the analyte concentration, with the results showing that the changes in the plasmon band position asymptotically change with the concentration of the analyte. Besides the shift in the plasmon band, changes in the intensity of the plasmon band and the peak width could also be observed. Such changes are key in monitoring minor concentration changes as is the case for biosensing applications.

We have previously shown the capability of the living tissue-like organism, the freshwater polyp Hydra vulgaris, to produce fluorescent and conductive fibers embedded into the animal tissues, containing thiophene-based compounds. We used these coelenterates as biofactories of novel biocompatible and conformable bioelectronic interfaces [1-2]. Here we show that biofiber production can be promoted by several human and murine cell lines and by other invertebrate in vivo models (such as the sea anemone Nematostella vectensis). The cell metabolic state and the animal developmental stage influences the fiber shape, amount and optical properties. In order to understand the mechanism underlaying the fiber biogenesis, we performed a systematic chemical engineering approach to identify the structure/groups involved in the spontaneous fiber assembling. On the other hand, we performed several physical and chemical treatments to identify the cell machinery components involved in the biosynthetic process. Finally, by mean of advanced characterization methods and holographic imaging we shed light on the mechanism of biofiber production and the fine structure, paving the way to new bioengineering concepts to fabricate novel living conductive materials.

A simple exponential model of diffuse reflectance for a two-layered medium was developed theoretically based on Monte Carlo simulation. Absorption and reduced scattering coefficients of these two layers were chosen to be different in which scattering property was dominant and the reduced albedo of the upper layer ranged from 0.8 to 0.99 and from 0.93 to 0.98 for the lower layer. Furthermore, the refractive index and anisotropy factor of these two layers were assumed to be equal 1.4 and 0.9 respectively. On the other hand, a finite element method was used to solve a diffusion approximation via COMSOL Multiphysics environment to compare the developed model with a diffusion approximation. The presented model has shown a low relative error, which did not exceed 20%. That was lower than the diffusion approximation results and it was in accordance with another complicated model developed by another research group. Consequently, the robustness of the presented model makes it more likely to predict a reflectance and reproduce the model to estimate a top layer thickness in real-time.

Materials with vanishing real part of the dielectric constant, called epsilon-near-zero (ENZ) materials, have gained a great deal of interest due to their exotic optical properties, yet their potential is limited by ohmic losses. We experimentally demonstrate a 1D periodic ENZ-dielectric material with enhanced optical transmission and giant polarization selectivity around the ENZ wavelength of the constituent ENZ-films, compared to bulk ENZ materials. The enhanced properties are physically attributed to Fabry-Pérot resonances and plasmon excitations in the film stack. Our material has applications e.g. in light sources with directional emission and coherence switching in lasers.

We demonstrated CO2 laser assisted processing of highly transparent (Ho0.05Y0.95)2Ti2O7 nanocrystalline coatings. The amorphous coating of the thickness of 577 nm was prepared by subsequent spin-coating of a colloidal solution followed by densification at 700°C in a radiation furnace. The densified coating was irradiated by a laser beam of a power density of 20 mW/mm2 for 60 s to induce the crystallization process. The nanocrystals formation caused the densification of the coatings reducing the thickness to 490 nm and increased the refractive index to 2.088. The coating exhibited strong luminescence at 2.1 and 2.95 μm corresponding to 5I7→5I8 and 5I6→5I7 electronic transitions, respectively. The corresponding time-resolved luminesce records showed the single-exponential decay course reaching the values of 8.4 ms and 0.221 ms for the emissions recorded at 2.1 and 2.95 μm, respectively. The demonstrated process can be used to prepare a luminescent coating with tailored properties. CO2 laser assisted processing can be used in a manner of direct laser writing for the preparation of integrated optical waveguides and amplifiers as a powerful alternative to conventional thermal processing.

We demonstrate alternating-current (AC)-driven colour-tunable organic light-emitting diodes (OLEDs) with vertically stacked green and red phosphorescent OLED units. Optically optimized thicknesses of hole and electron transporting layers were investigated through optical simulation. In addition, two types of red host materials were used for the red OLED unit, and the red OLED unit with 4,4′-Bis(N-carbazolyl)-1,1′-biphenyl showed higher current efficiency compared to that of the red OLED unit with 2,6-Bis(3-(9H-carbazol-9-yl)phenyl)pyridine. The fabricated colour-tunable exhibited red and green colours when the duty ratio was 1% and 99%, respectively. Furthermore, the device can produce various colours that are a mixture of green and red by adjusting the AC-driving duty ratios.

Vanadium dioxide (VO₂) exhibits a reversible first-order semiconductor-metal phase transition (SMT) near 68 °C at ambient pressure, consisting in a structural transformation from a low-temperature semiconducting monoclinic phase to a high-temperature metallic rutile phase. This phenomenon is investigated on thin films of VO₂, with thickness ranging from 15 to 300 nm, which are deposited on a silica substrate by magnetron sputtering. The films are systematically characterized at the morphological, structural, and optical level by using Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Grazing Incidence X-ray Diffraction (GIXRD), Raman Spectroscopy, Spectrophotometry, and Spectroscopic Ellipsometry. The SMT transition is investigated in-situ by Optical Spectroscopy in the VIS-NIR spectral range and by Grazing Incidence X-ray Diffraction (GIXRD). Compared to their bulk counterpart, thin films display broader phase transitions upon thermal excitation. This is evidenced by monitoring the temperature-dependent transmittance at specific wavelengths which reveals a hysteretic behaviour, whose thermal width is larger for smaller thicknesses. Additionally, changes in peak positions and intensities in in-situ GIXRD diffraction spectra further elucidate the phase transition dynamics.

Crystalline coating materials like AlGaAs/GaAs have the potential to revolutionise applications in high-precision optical metrology, such as ultra-stable laser cavities or gravitational wave interferometers.

The primary driver for that is the promise of reduced noise and, thus, enhanced stability and measurement sensitivity. However, recent investigations revealed that the aspired noise level could be out of reach as an additional noise source is present, seemingly originating from intrinsic material properties and being related to the illumination of the material. To contribute to understanding this effect, we employ mechanical spectroscopy to explore the illumination-dependent mechanical loss of GaAs flexures at mechanical frequencies from 100 Hz to 94 kHz. The results indicate that photoinduced effects in bulk GaAs change the elasticity and mechanical loss with relaxation times of several minutes.

In this work, we report giant (by up to three orders of magnitude) enhancement of second harmonic generation (SHG) from halide double perovskite single crystals, which occurs at low temperatures under light illumination. We attribute this enhancement to a build-up of a light-induced surface electric field that is predominantly oriented orthogonally to the sample surface, as deduced based on the six-fold rotational symmetry of the SHG azimuthal pattern. The formation of the surface electric field is explained by photo-induced charge transfer from deep surface-related states to traps in the bulk region or vice versa, driven by diffusion. Our findings, therefore, highlight the importance of the surface states in double perovskites, which could be used to enhance the non-linear properties of these centrosymmetric materials.

Lasing at room temperature from triangular plasmon lattices of aluminum particles coupled to a solid-state polymeric-dye layer is reported. A homemade double rotation stage was used to measure the optical response of the samples and their lasing emission properties. Keeping the shape of the particle and the symmetry of the arrays, the study of two lattices with different lattice parameters shows a good quality of the lasing action when the lattice plasmon wavelength is fixed to improve the overlap with the emission wavelength by the emitter, corroborating previous evidence.

We synthesised CdS Q-dots and Dy3+ doped CdS Q-dots dispersed in borosilicate glasses and evaluated their optical and NIR photoluminescence properties. When excited with an 800nm source, new strong photoluminescence emissions from 850 to 1150 nm were observed in the NIR are reported. These new find states may be attributed to NIR virtual or trap states of the CdS S-Qdot. The strong photoluminescence emission spectrum observed from 850 to 950 nm corresponds to electron–hole recombination for as-prepared CdS-Q-dot glasses. However, this photoluminescence emission disappeared upon heat treatment due to photoluminescence emission from defect states.

Recent commercial organic light-emitting diode (OLED) devices rely on vacuum deposition techniques for enhanced durability and efficiency. Research has concentrated on optimizing layers like the emitting layer (EML), hole transport layer (HTL), and electron transport layers (ETL) [1]. Carbazole-based mCP is commonly used as a host material due to its simple structure and high triplet energy (2.9 eV) [2]. However, challenges such as low thermal stability and short lifetime necessitate solutions [3].

This study addresses these issues by synthesizing a new host material, Ad-mCP, by incorporating adamantane into mCP (Figure1). Ad-mCP exhibits superior film formation and thermal stability compared to mCP (Figure 2a). Additionally, the study demonstrates the stable implementation of a blue OLED device using Ad-mCP. Comparative analysis with mCP-based devices shows Ad-mCP's higher performance (EQE max = 29.9%, CE max = 30.6 cd/A, PE max = 32.0 lm/W) in Figure 2b. In summary, the proposed blue TADF OLED device with Ad-mCP offers better thermal stability and optical/electrical performance than mCP-based devices. This highlights the potential of Ad-mCP for vacuum deposition processes in blue TADF OLED devices.

Vanadium dioxide (VO2) is a thermochromic material presenting an isolator-to-metal transition (IMT) around 68°C and a huge variation of absorptivity/emissivity in the mid infrared. This IMT material has been investigated for spectral–selective applications, notably windows coatings, and may play a role in more advanced applications combining photonics and thermal properties. In the present study, we report synthesis of VO2 thin film obtained by Atomic Layer Deposition (ALD). As deposited and annealed samples of VO2 grown by the two techniques have been analyzed and compared chemically and structurally. The thermo-optical properties of VO2 samples around IMT were analyzed with spectroscopic ellipsometry, UV-VIS spectrophotometry, FTIR (Fourier transform infrared spectroscopy) and RAMAN spectroscopy. Optical studies have shown a very weak absorptivity/emissivity variation in the UV and visible spectrum contrary to the mid to long infrared where samples showed a major evolution going from around 20% for low temperatures to around 80% after phase transition.

It has been observed that VO2 samples oxidize under ambient conditions to a more stable phase (V2O5), making disappear ambient temperature IMT transition. The effects of capping layers such as Nb2O5, Ta2O5 and TiO2 that might prevent the alteration of the VO2 thin films will be presented.

We will present a rapid and non-destructive technique for the measurement of the mean diameter of a silica nanofiber using the wavelength position of the signal peak in a spontaneous four wave mixing experiment. The nanofiber diameter can be characterized in a range going at least from 650 to 1250nm. Several nanofibers were characterized, and the measured diameter show a good accordance with the one obtained using a Scanning Electron Microscope. The technique is simple to use and has even the potential to be implemented in situ in order to realize a diameter measurement during the pulling of the nanofiber for a better control of the final diameter of the nanofiber.

We report the generation of Airy pulses in an injection-seeded, amplified fiber loop incorporating an acousto-optic frequency shifter and a dispersive delay line implemented through a series combination of linearly chirped fiber Bragg gratings. The combined effect of unidirectional frequency shifting and first-order dispersion generates a frequency comb with cubic spectral phase, equivalent in the time domain to a single-sided, bandlimited Airy pulse train. The present approach demonstrates the use of intra-loop phase-only filtering for the generation of tailorable optical waveforms in recirculating fiber loops.

The LIBS technique is evaluated for its application to the analysis of Cadmium (Cd) in Ecuador's cocoa beans. Cd quantification is crucial for public health, the environment, and agriculture. A systematic pellet preparation method was established, mixing cocoa powder with known cadmium nitrate amounts. LIBS plasmas were generated in air and nitrogen atmospheres using a pulsed Nd: YAG laser (1064 nm, 8 ns; 75 mJ/pulse). Spectral emissions were examined for optimal experimental conditions (Delay time:3 µs; 75 mJ/pulse; LTSD: 82 mm). A second and third-order minimum-based algorithm was employed to efficiently eliminate background interference while retaining the information inherent in the characteristic spectral lines. This approach enabled successful identification of the essential Cd emission peaks while mitigating the matrix effect associated with cocoa powder. Despite differing from prior studies due to concentrations, the technique qualitatively detected significant Cd via the 346.766 nm and 361.051 nm peaks.

Raman technology offers a cutting-edge approach to measuring glucose solutions, providing precise and non-invasive analysis. By probing the vibrational energy levels of molecular bonds, Raman technology generates a unique spectral fingerprint that allows for the accurate determination of glucose concentrations. This study proposes the use of Raman spectroscopy to identify different glucose concentrations through the detection of Raman fingerprints. As expected, higher concentrations of glucose in the solution conducted to higher peak bands, indicating more glucose molecules interacting with light and consequently increasing the magnitude of inelastic scattering. This non-destructive approach preserves sample integrity and facilitates rapid analysis, making it suitable for various applications in biomedical research, pharmaceutical development, and food science.

Optical fiber sensors were implemented to measure in-situ temperature variations in an oscillatory flow crystallizer operating in continuous. The sensors were fabricated by cleaved in the middle 8 mm-length fiber Bragg gratings, forming tips with a Bragg grating of 4 mm inscribed at the fiber ends. The geometry of the sensors fabricated, with a diameter of 125 µm, allowed the temperature monitorization of the process flow, inside the crystallizer, at four different points: input, two intermediate points, and output. The results revealed that the proposed technology allows to perform an in-situ and in line temperature monitorization, during all the crystallization process, as an alternative to more expensive and complex technology.

Distributed acoustic sensing (DAS) is a sensing technique that allows continuous data acquisition of strain rate and temperature with exceptional spatial resolution, up to few meters, for extensive lengths up to 100 km. The ubiquitous nature of optical fiber cables rendered DAS an appealing alternative for geophysical sensing, allowing cost-effective data collection with extensive spatial coverage leveraging existing infrastructure. This study presents findings from the deployment of a DAS system on a dark fiber located on the Madeira Island, Portugal. Through the implementation of 2D filtering, simultaneous analysis of data from road traffic, ocean waves, and seismic activity was achieved.

Azobenzenes are a class of compounds presenting photoisomerization capabilities that allow the

writing and erasure of birefringence along a desired direction. This feature enables applications requiring

polarization control, which although have been extensively investigated in the visible light spectrum, poor emphasis

has been paid to the infrared region. In this paper, a systematic characterization of induced birefringence

creation and relaxation dynamics has been carried out in azopolymers thin films in the infrared telecommunications

region of 1550 nm. This study covers both birefringence characterization in terms of wavelength and

irradiance of birefringence writing beams. Preliminary results revealed remarkable maximum birefringence

values as high as 0.0465 attained during the recording phase, that stabilized at 0.0424 during the relaxation

phase, which is quite promising for many applications.

Spreading optics and photonics arises as a pivotal duty for researchers in the field, aiming to inspire new generations of students to pursue a scientific career. Furthermore, essential abilities for researchers such as explaining science to an audience or approaching abstract concepts in a visual manner can be easily learnt whilst performing science fostering activities. With these ideas in mind, USCOPTICA Student Chapter and Santiago USC YM Sections were born. Bachelor and Master students and early-stage researchers collaborate in our group, performing diverse outreach sessions, comprising hands-on scientific workshops in schools and science diffusion events, roundtables raising awareness on social issues in Academia and cycles of conferences in collaboration with other student groups. The following abstract aims to share with the scientific community our major activities in the last two years.

Recent pandemic stressed out the necessity to develop new and efficient biosensor system for the detection of airborne pathogens. A new, simple strategy is presented for the optical biosensing of airborne pathogens employing vibrational spectroscopy interrogation and nanostructured platforms. As a proof of concept, we pay attention to SARS-Cov-2 virus, using its spike glycoprotein as optical biomarker. Here, we report the main steps in the optical biosensor development, from the vibrational characterization of biomarker and its structural investigation to the potential nanostructured substrates. These results constitute only the preliminary first steps anyway, the suggested approach could represent a prospective label-free promising tool for a wide range monitoring of pathogens in air in close environments.

Surface-Enhanced Raman Scattering sensing devices offer significant advancements in food quality and safety monitoring by providing rapid, on-site detection and real-time analysis. Integrating noble metal nanoparticles with flexible cellulose substrates, particularly bacterial cellulose (BC), enhances Raman signal amplification due to BC's high purity, porosity, and distinctive network structure. BC’s mechanical strength and adaptability to various shapes make it an ideal foundation for flexible SERS substrates. Studies have shown BC-based SERS substrates' effectiveness in detecting various chemicals, including rhodamine 6G, thiram, and atrazine. This study introduces a method for synthesizing gold nanoparticles (AuNPs) directly within a BC matrix, resulting in a hybrid material with exceptional structural integrity and uniform AuNP distribution. Characterization using Atomic Force Microscopy (AFM) confirms the material's uniformity and flexibility, crucial for reliable sensor applications. The BC-AuNP hybrid demonstrates high sensitivity and selectivity in detecting pesticide residues and other contaminants, highlighting its potential for practical applications in food safety. This innovative approach not only advances agri-food sensing but also aligns with environmental sustainability, offering a reliable, efficient solution for real-time monitoring and improving food safety standards.

Spectroscopic applications strive for high spectral resolution and broad bandwidths, often facing a tradeoff between the two. Recent advancements in super-resolved spectroscopy offer promising solutions, particularly beneficial for compact and cost-effective instruments in various fields like sensing, quality control, environmental monitoring, and biometric authentication. These techniques, employing sparse sampling, artificial intelligence, and post-processing reconstruction algorithms, enable efficient spectral investigation.

Reconstructive spectroscopy, a versatile processing technique, reconstructs signals from a limited number of measurements under the assumption of signal sparsity in a chosen domain (e.g., Fourier or wavelet components). Resolution enhancement via spectral reconstruction has been successfully demonstrated. By projecting the target spectrum onto a random basis of non-ideal broadband spectral filters and utilizing regularization algorithms, highly resolved spectral signals can be reconstructed, even below the Nyquist sampling theorem.

In this study, we show that enhanced spectral resolution is achievable using broadband optical filters with smoothly varying, angular-robust transfer functions. The selection of smooth transfer functions ensures sufficient spectral diversity to computationally retrieve sparse and denser signals accurately

The use of patterned surfaces to tailor the frequency response of magnetic materials is of utmost importance in the field of magnon-spintronics and microwave photonics due to their potential to allow the design and development of exciting technological applications such as microwave delay lines, high frequency and bandwidth CHIRP signal sources and microwave sensors, among others. Here, we demonstrate a method to fabricate one- and two-dimensional magnonic crystals with arbitrary symmetry and use it to engineer the amplitude-frequency characteristic of magnetostatic surface spin waves excited in a magnetic material. The technique is based on the gentle microablation of the sample surface by focused femtosecond laser pulses. Constrain the illumination in a tiny spot consents the use of modest energy levels and enhance the achievement of micrometre precision. The induced changes in the measured transmission characteristics reveal the strong and complex symmetry-dependent interaction of the spin waves with Bravais and non-Bravais lattices. The microfabrication method described here facilitates and speeds up the realization of complex magnonic and photonic components and provides an efficient tool to explore complex microwave and magnetic dynamics in scattering lattices.

We utilize hyperspectral imaging (HSI) technique for detecting and characterizing black microplastics (BMPs) in water samples directly. We fabricated nine BMP samples from common daily life plastics using a metal work file with a diameter of approximately 200 mm. We discovered that, regardless of all these samples appearing black to the human eye, different BMPs have distinct spectral profiles observable in the visible, and near-infrared regions. Furthermore, we explored the impact of varying BMP quantities in the water samples and found that the reflectance of black microplastics may be influenced by the quantity of BMPs present in the sample.

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We investigate diamond nitrogen-vacancy (NV) centers as alternative labels in stimulated emission depletion (STED) microscopy. To this end, artificial diamond is used as a substrate and Raman spectroscopy in photoluminescence (PL) mode is performed for clearly identifying the emission wavelengths of the NV centers. With the aid of a STED microscopy system, we imaged a random feature on substrate surface with the NV-centers in STED and confocal mode. Our first measurements indicate that the combination of NV centers and STED is very promising for resolving the structures and can be further extended to nanoscale structures applied on the diamond substrates.

We introduce a polarimetric method for measuring the electromagnetic temporal degree of coherence of a quasimonochromatic, partially polarized, and partially coherent light beam. In particular, we measure the polarization Stokes parameters at the output of a Michelson interferometer as a function of the time delay, which allows us to deduce the degree of coherence of the input beam. To demonstrate the method, measurements are performed with laser diode and filtered halogen sources.

We present a two-wavelength digital holographic microscopy setup for surface topography measurement with single-point illumination and a method for correction of unwanted phase drifts using secondary reference waves.

Ultrafast laser pulses are used in various applications such as high-harmonic spectroscopy or ultrafast imaging. In these applications the pulse characterization (amplitude and phase) is highly important, SHG-FROG being one of the techniques used. This method uses different algorithms to retrieve the ultrashort pulse amplitude and phase. In this research, convolutional neural networks (CNN) are used to characterize the ultrashort laser pulses. The CNN is specifically tailored for the laser system operating at the ELI-RO facility. The data on which the neural network is trained, validated and tested incorporates parameters from the chirped pulse amplification stage of the laser system. Good agreement between the original field and the retrieved spectral electric field are obtained, demonstrating the ability of CNN to reconstruct ultrashort laser pulses from FROG spectrograms.

Non-destructive testing (NDT) techniques serve as indispensable tools across diverse industries, facilitating material and component inspection without inflicting damage. This article underscores the paramount importance of NDT methods in enhancing product quality, safety, and cost-effectiveness. Leveraging advanced techniques such as shearography, ultrasonic laser, and thermography, manufacturers can proactively identify defects during the production process, thereby reducing scrap and rework costs while enhancing overall product integrity. Shearography excels in surface defect detection, while ultrasonic laser offers sensitivity without necessitating direct contact, and thermography enables versatile temperature-based inspection. The synergistic coexistence of these techniques within NDT protocols maximizes inspection efficacy, ensuring high-quality and safe outcomes across various industries. By embracing a comprehensive approach to NDT, industries can optimize operational efficiency, minimize risks, and uphold stringent quality standards. In conclusion, the integration of shearography, ultrasonic laser, and thermography in NDT practices represents a cornerstone in maximizing inspection effectiveness and maintaining superior quality and safety standards across industrial sectors. This research was funded within the European MISE project LAMPO - Leonardo automated manufacturing processes for composites – CUP C78I20000060008

Chiral optical forces exhibit opposite signs for the two enantiomeric versions of a chiral molecule or particle. If large enough, these forces might be able to separate enantiomers all-optically, which would find numerous applications in different fields, from pharmacology to chemistry. Longitudinal chiral forces are especially promising for tackling the challenging scenario of separating particles of realistically small chiralities. In this work, we study the longitudinal chiral forces arising in dielectric integrated waveguides when the quasi-TE and quasi-TM modes are combined, for enabling the separation of absorbing and nonabsorbing chiral particles. We show that chiral gradient forces dominate in the scenario of beating of nondegenerate TE and TM modes when considering non-absorbing particles. For absorbing particles, the superposition of degenerate TE and TM modes can lead to radiation pressure chiral forces that are kept along the whole waveguide length. We accompany the calculations of the forces with particle tracking simulations for one specific radius and chirality parameter and show that longitudinal forces can separate chiral nanoparticles suspended in water even for relatively low values of the particle chirality.

This paper presents a comprehensive simulation study on the design and simulation of an electro-optic ring switch utilizing graphene material. The switch employs the electrically Tunable Refractive Index by graphene to modulate the transmission characteristics within a ring resonator structure. By applying an electrical voltage ranging from -6 to -10V, significant changes are noticed in the output ports' transmission characteristics. In particular, the transmission through the output ports varies between 81% to 18% for output port n.1 and 21% to 83%for output port no.2, proving that signal propagation can be effectively controlled and manipulated. In addition to demonstrating the electro-absorption capabilities of graphene, this study explores the complex mechanics involved in the switching process. The relationship between the applied voltage and the optical characteristics of graphene is clarified by thorough simulations, providing insight into the switch's dynamic behavior. Furthermore, the efficiency, response time, and Electrical bandwidth of the device are discussed, offering a glimpse into its possible use in photonic integrated circuits and telecommunications. Overall, this study not only unveils the promising prospects of graphene-based electro-optic ring switches but also contributes to advancing the understanding of novel materials for next-generation photonic devices.

In this work, we propose the design of a compact optical switch featuring a wide bandwidth of 360 nm, suitable for telecom operations. The switch is a passive 3dB splitter realized through a Y-branch, electrically activated via a graphene/insulator/graphene (GIG) capacitor embedded within the rib waveguide (WG). The capacitor itself is embedded within an SOI-based hybrid WG composed of crystalline (c-Si) and hydrogenated amorphous silicon (a-Si:H), with the GIG between the two layers. Such a photonic structure optimizes the light-matter interaction and enables a compact device with a length of only 100 μm. By applying a voltage bias to the graphene layers, we achieve the condition necessary for efficient data transmission through the WG. Indeed, the electrical doping of graphene enables the modulation of optical losses within the waveguide, ranging from total light absorption to up to 70% transmission. The simplicity and ease of fabrication of this innovative design offer significant advantages for integration into existing photonic circuits. Its wide bandwidth allows compatibility with a variety of telecom wavelengths, providing flexibility in network configurations. Consequently, this compact optical switch presents a promising solution for modern data communication needs, demonstrating a balance between efficiency and scalability.

The propagation and bend excess loss characteristics of silicon nitride strip waveguides at an 850 nm wavelength were explored in this study. The aim was to optimize fabrication processes using machine learning, particularly gradient-boosted forests, to achieve low-loss photonic integrated circuits (PICs) and accurately predict the losses. The impact of waveguide geometry and layer properties on loss was examined using a full factorial design of experiment. These machine learning models' predictive accuracy and ability to capture complex relationships between fabrication parameters and different loss mechanisms were assessed. Key parameters and interactions were identified, improving PIC efficiency for photonic sensing applications.

Coherent photonic biosensors have proven to be excellent for detecting biomarkers in various applications. The development of multiplexed systems capable of simultaneously detecting multiple biomarkers from a single sample remains challenging. Typically, biosensing systems achieving lower limits of detection (LOD) are using photodiodes for the detection process, typically limiting their multiplexing scalability. In this work, the use of a camera is proposed to overcome this limitation. The performance of the biosensor is analyzed based on a comprehensive signal and noise model of a camera system. It is experimentally shown that an LOD of ~10-7 RIU can be achieved by optimizing the image acquisition parameters.

This work aim to determine a Single Mode (SM) Silicon-On-Insulator (SOI) rib waveguide using Machine learning (ML) techniques, which learn automatically by matching the input data with the target property. Random Forest (RF) is the ML algorithm used in this work. The accuracy of the model reaches 99% by using R2 score. The device is a rib waveguide based on Silicon (Si), with a cladding made of Silica (SiO2). The results obtained illustrate the conditions for SM, with the width and the rib etch-depth found to be relatively smaller compared to the total thickness. The ML approach have proven to be quick and effective regarding this problem.

In this work, we assessed by means of numerical simulations the observability of mid-infrared intersubband polaritons in hole-doped Ge/SiGe multiple quantum wells embedded into stripe microcavities consisting of an upper gold grating and a bottom highly n-doped SiGe mirror.

In this paper, an electrically controlled liquid crystal (LC) microlens array based on dual-layer arrayed planar pattern electrode is reported for effective light wave modulation. By adjusting the voltages applied to two planar arrayed electrodes within one substrate of the LC microlens, an adjustable focused circular ring or point-shaped light spot can be formed. Dual-layers arrayed pattern electrode with a minimum interval spacing of approximately ~10μm and a maximum of 130μm are achieved on one substrate by using standard microelectronic lithography, etching, coating film, and other processes. Experimental results are presented and discussed to illustrate outstanding performance of electrically focusing and modulation capability of the proposed LC device. This approach will serve as inspiration for the continued development and design of LC optical elements, enabling applications such as light field imaging, wavefront detection/correction, and the advancement of imaging augmented systems.

Bound states in the continuum (BICs) are exceptional electromagnetic modes that exist within the radiation continuum but do not interact with it, exhibiting infinitely high Q-factors due to their non-radiative properties. These features make BICs highly advantageous for applications in photonics and optical engineering, particularly in biological and chemical sensing. This study presents recent findings on the utilization of a devised BIC-sensor platform for investigating the dissociation constant between SPARC protein and Human Serum Albumin (HSA). SPARC, also known as osteonectin, is a multifunctional protein involved in bone mineralization, angiogenesis, and inflammation regulation. By the real-time monitoring of the interaction dynamics between SPARC and HSA, this research offers insights into their roles in physiological processes and pathological conditions, contributing to the advancement of biomedical research and potential therapeutic interventions.

Stimulated Raman scattering (SRS) microscopy is able to perform high sensitivity biological imaging with high spatial and spectral resolution and image acquisition time of a few seconds. Nevertheless, SRS images often suffer from low SNR, due to the weak Raman cross-section of biomolecules. Therefore, methods aiming to improve image quality are mandatory. In this paper, the performances of a 2D denoising algorithm based on SSA is analysed. SRS imaging of lipids droplets have been used in order to validate our algorithms.

Low-emissive Transparent Conductive Oxide (TCO) coatings, such as Indium Tin Oxide

(ITO) films, can be used to reduce radiative losses that affect Hybrid photovoltaic-thermal (PV-T) devices. This work shows the optical properties of ITO deposited by magnetron sputtering on a glass substrate with and without thermal heat treatment at different temperatures. All the analyses conducted include UV-VIS and infrared regions, up to 20 μm.

We apply the recent advances on the Singularity Expansion Method obtained in the field of the scattering matric theory for non-Hermitian physics to derive an analytical model of the dielectric permittivity of optical materials [1-3]. The dielectric permittivity is considered as a linear transfer response function linking the displacement field to the electric field which allows us to prolongate the function into the complex frequency plane with the Singularity Expansion Method [3]. The question is to know whether the Drude-Lorentz models that are based on microscopic models comply with this approach and complex analysis. We show that this approach allows us to generalize the Drude-Lorentz model [4]. We apply the generalized expression to fit experimental data of ε(ω) for several materials, in particular metals, dielectrics and 2D materials. We show that in all cases, the generalized model outperforms conventional Drude-Lorentz models [4].

References

[1] V. Grigoriev et al., Phys. Rev. A 88, 011803(R) (2013).

[2] R. Colom et al., Phys. Rev. B 98, 085418 (2018); I. Ben Soltane et al., Laser Photonics Rev. 13, 2200141 (2023)

[3] I. Ben Soltane et al. New J. Phys. 25, 103022 (2023)

[4] I. Ben Soltane et al. Adv. Optical Mater. 12, 2400093 (2024)

The combination of Fourier-transform infrared spectroscopy and scattering-type scanning near-field optical microscopy allows for the spectroscopic investigation of materials and structures at the nanoscale, far below the diffraction limit in the infrared. This resolution is achieved by the use of metallized atomic force microscopy tips which locally illuminate the sample through the creation of near-fields at their apex. The complex interaction between incident light, a metallized tip and a layered sample necessitates the use of sophisticated models. While these models are powerful, using them to fit measured spectra is generally slow and often unstable, thus requiring expert oversight. Neural networks present a fast and often more stable alternative, but their application so far has focused on bulk samples. Here, we present the use of convolutional neural networks for the recovery of the optical and thickness properties from the spectra of samples consisting of one or two layers of polar crystals on silicon.

We have developed an interferometric optical reflectivity microscope to observe the phase-sensitive reflectivity of nanophotonic structures with high spatial and spectral resolution over broad frequency ranges from 4000 to 13300 cm-1, corresponding to wavelengths 750 < λ < 2500 nm. From the frequency-resolved phases we obtain the (group) time delay. We study planar microcavities made from GaAs/AlAs, and three-dimensional (3D) photonic band gap crystals made from silicon with the woodpile structure. Measurements on planar microcavities have been compared with analytic transfer matrix theory, where an excellent agreement is found. The mean difference between measured and calculated reflectivity is better than 4 percent-points. For a planar microcavity with a stopband centred at 1331 nm and a relative bandwidth of 16% we observe time delays exceeding 4 ps at the edge of the stopband. For the 3D woodpile structure we observe time delays exceeding 550 fs at the edge of the 3D bandgap. Combined with the very thin metasurface like structure, this yields a lower bound for the group index of n_g≥210, much more than previously observed in photonic crystal waveguides. Current studies include developing a model for the 3D woodpile crystal to understand the large group delay.

A novel design for an optomechanical cavity consisting of a series of rectangular silicon nanobricks, with each brick acting as an independent mechanical resonator but all coupled to a same optical field, is proposed, and numerically demonstrated. Each brick is placed on top of a thin silica pillar that provides mechanical support whilst isolates the individual mechanical resonances. The mass sensing capabilities of this cavity are studied through numerical simulations, proving that a point mass approximation can be used for silica nanoparticles with radius smaller than 100 nm, and that different nanoparticles can be measured independently but simultaneously.

We studied by FDTD computer simulations the dependence of the surface plasmon resonances in linearly arranged gold nanospheres on incident light polarization, spheres number and diameter, and interparticle gap. The observed scattering spectra of large particles show a particularly interesting behaviour, with coupled plasmon resonances that can be either red or blue shifting with the modification of the interparticle gap. The sensitivity of the various observed coupled plasmon modes to refractive index variations is then evaluated.

We provide the framework and the tools for canonical quantization of plasmon polaritons from metallic or dielectric finite nanostructures. They allow one to diagonalize the Hamiltonian and to exactly determine the quantized electromagnetic field and an imaginary Green’s tensor identity satisfying the Sommerfeld radiation boundary conditions.

Since Veselago explored metamaterials with negative permittivity and permeability in 1968, there has been significant evolution in nano-optics/photonics. Metamaterials have progressed from utilizing metals (Au, Ag, Al, etc.) to high refractive index (RI) dielectrics (Si, Si3N4, TiO2, etc.) over the past few decades. Recently, more and more research has focused on dynamically-tunable metamaterials, which allow for manipulating material optical properties through external stimuli, significantly expanding the applications of nano-optics/photonics. However, most research still concentrates on changing the optical properties by covering tunable materials on static materials (metal and dielectric). This project investigates the optical properties of pure tunable metamaterials (WO3), which exhibit a more extensive tunable range, lower optical losses, noble metal free, etc. It initially demonstrates the vast potential of dynamically-tunable metamaterials in ultra-high-resolution displays spanning near-eye augmented reality/virtual reality (AR/VR).

We have developed an optical fiber-based module that can select, retrieve, and transfer single cells and cell clusters. Cell picking and isolation has several applications like separating circulating tumor cells, isolating single fetal cells for prenatal testing, and others. Our Lab-in-a-Fiber (LiF) module can detect fluorescent cancer cells (MCF-7) from a mixture of labeled and unlabeled cells and pick them up for further analysis. The cells picked up by the fiber show a 90% survival rate on viability tests, making this cell-picking technique an attractive alternative to existing methods.

We present an analytical model for measuring the dispersion of integrated waveguides, leveraging the Michelson interferometry effects observed in devices with chirped Bragg gratings. Building on our previous experimental work, we derived a theoretical framework that simulates the group delay and subsequent dispersion values from the reflected spectrum of a device under test (DUT) which is a linearly chirped Bragg grating fabricated on a silicon-on-insulator (SOI) platform. This model incorporates the principles of interference fringes generated by reflections within the waveguide, enabling a precise calculation of group delay (τ) in the DUT as a function of frequency. Our model predicts the dispersion by determining the spacing between the peaks (∆f) from the local period of the interferometric fringes, with τ being inversely proportional to ∆f. Simulations were conducted on a DUT that is designed to produce a dispersion of -45.9 ps². The model yielded a dispersion of -45.6 ± 0.67 ps², demonstrating close alignment with both the theoretical design and our experimental results, which recorded a dispersion of -45.5 ± 11.2 ps² from 7 different DUTs that were measured.

This work presents innovative methods for visualizing inhomogeneities and stress distributions in Ti:Sa (titanium-doped sapphire) crystals, which are challenging to assess due to their birefringent nature. Two experimental approaches were developed: the first enables two-dimensional mapping of the Figure of Merit (FoM) and absorption at wavelengths of 532 nm, 780 nm, and 1550 nm, revealing variations in absorption across the crystal. The second experiment utilizes circularly polarized light and polarization imaging to detect internal stress and defects. The results demonstrate the successful visualization of lateral absorption, stress, and core features within the crystals, offering insights into their optical quality. These techniques provide new possibility for evaluation of laser materials, with significant implications for improving the manufacturing and selection processes of Ti:Sa crystals in advanced laser applications.

The gap states of a random Fibonacci-on-average multilayer exhibit strong localization and high Q- factors, indicating potential suitability for random lasing applications. This study investigates the gain threshold behavior of random lasing within the visible spectrum. Using the scattering matrix method with complex refractive indices, our simulations examine the relationship between the gain threshold, structural disorder, and the number of layers. The results contribute to the understanding of random lasing behavior of this type of quasi-crystal.

In the present study, we focus into the infrared radiation (IR) absorption coefficients of several polymer types to propose a novel approach through the development of radiative-cooling polymeric films and composites. We will firstly describe the process of samples preparation. Afterwards, we will introduce the experimental setup employed for linear optical characterization in the infrared range along with the obtained experimental results. Finally, we will give details about the numerical model that we developed in order to evaluate the radiative cooling effectiveness of the different films.

Sensitive and reliable characterization of chirality in nanostructures and molecules is of great importance in multidisciplinary research combining physics, chemistry and nanotechnology, with potential applications in pharmaceutical and agrochemical industry. Chirality is connected to circular dichroism (CD) - the absorption difference when the chiral medium is excited with circular polarizations of opposite handedness. Hence, measuring chirality by direct absorption measurements is of great interest in nanophotonics and plasmonics community, where the nanostructured media can enhance chiro-optical effects. Here we present a recently constructed photo-acoustic spectroscopy (PAS) set-up, which offers many degrees of freedom in characterization. We use a laser which is widely tuneable in the near-infrared (680-1080 nm) and visible (340-540 nm) ranges. The laser output is modulated with a mechanical chopper, where its frequency defines the penetration depth of the thermal signal. The input polarization is controlled by a linear polarizer and a quarter-wave plate, and the laser can be focused before impinging on the sample in the tightly closed photo-acoustic cell. The cell is placed on translational and rotational stages, which allows for the spatial mapping and extrinsic chirality measurements. Finally, a sensitive microphone measures the pressure changes in the cell, enabling scattering-free measurement of absorption and CD.

Breast cancer is still the most diagnosed one and represents the leading cause of tumour death among women, determining an urgent need for new tools demonstrating early diagnostic, prognostic, and monitoring potential. Among all possible strategies, those based on multimodal approaches offer huge advantages for these purposes, since they join orthogonal techniques in a single device and thus have broader feedback on a specific pathology.

In such a context, the aim of the JUNCTION project is to design and realize a new fiber optic probe, to integrate a single fiber bundle for a minimally invasive investigation. It merges Surface Enhanced Raman Spectroscopy (SERS) and Time Domain Diffuse Optics (TD-DO) techniques for breast cancer diagnosis being sensitive to the overexpression of specific biomolecules (i.e.: epidermal growth, factor receptor 2, mucin 1, microRNAs) and to average tissue composition (i.e.: collagen, hemoglobin, water), respectively. In this contribution, the ideas underlaying the project will be illustrated and the main implementation strategies will be discussed with regard to both the TD-DO- and SERS–based fiber optic probe. Finally, preliminary results will also be presented.

Project JUNCTION-PRIN2022-prot. 20225MR35K

Plasmonic and Photonics applications of superconducting materials, suggested at first by the necessity to minimize the dissipative losses of conventional metals in the high frequency ranges, are topics of growing interest in Optics. In this perspective, GdSr2RuCu2O8-d (Gd1212) Rutheno-Cuprate Superconductor presents very promising properties, showing both superconducting and magnetically ordered phases coexisting in the same cell. To investigate its features, the fabrication of macroscopic crystallographically oriented samples is necessary. The use of melt texturing techniques has shown to be among the most effective ways to achieve the best characteristics, although the fabrication of high-quality Gd1212 samples is intrinsically difficult.

To reach a better understanding of Gd1212 incongruent melting reaction, a series of bulk samples annealed at temperatures below and above the melting temperature was prepared. Raman Microscopy and Mapping performed on molten and re-solidified samples revealed the presence of different phases, corresponding to those identified in our previous studies. These observations were also confirmed by XRD, TGA-DTA, and SEM+EDS characterisations. Secondary phases formation showed a strong dependence on the temperature of the annealing treatments.

Susceptibility and magnetization measurements show both superconducting and magnetic transitions and a contribution of different spurious magnetic phases as suggested by EDS.

Phase-based sensing can reach a very high level of accuracy, and integrating these devices on a silicon chip can make these devices extremely compact and very affordable. In this presentation, I will report some recent results of photonic sensing on chip using phase-based measurements. In particular, I will show demonstrations of integrated wavemeters on chip at high speed using carrier-depletion-based modulation, and refractive index sensing experiments based on actively-modulated interferometers.

We report recent progress on optoelectronic devices and metasurfaces involving surface plasmons, enabled by metal-oxide-semiconductor (MOS) structures on Si and on epsilon-near-zero materials. We discuss electrically tuneable metasurfaces, high-speed electro-absorption modulators, and reflection modulators. Hot carriers created by the absorption of plasmons in metallic nanostructures on MOS structures are also discussed as they lead to novel device physics that open the door to new device concepts.

Subwavelength engineering has become established as an essential design tool in integrated photonics. The utilization of state-of-the-art semiconductor manufacturing methods to create nanostructures within optical waveguides has provided unparalleled control over the manipulation of light propagation in silicon photonic chips. In this presentation, we will present our recent breakthroughs in this rapidly advancing field. We will also introduce a nascent research area of resonant integrated photonics, leveraging Mie resonances in dielectrics for on-chip guidance of optical waves, as well as Dirac gratings and parity-time symmetric waveguide structures.

Maxwell's equations are solved if and only if the amplitude and phase of the total electromagnetic fields are determined across all spatial points. Typically, the Stokes parameters can only capture the field's amplitude and polarization in the (far) radiation zone. Thus, relying solely on the measurement of the Stokes parameters proves insufficient to solve Maxwell's equations.

In this talk, I present a method that successfully solves Maxwell's equations for widely studied objects in Nanophotonics using only the Stokes parameters. This feature endows the Stokes parameters, primarily used to gain insight into the polarization state of electromagnetic radiation, with an even more fundamental role in electromagnetic scattering theory. Consequently, our findings, supported by analytical theory and exact numerical simulations, can find applications in all branches of Nanophotonics and Optics.

We show that certain desired behaviors of optical metasurfaces (e.g large amplitude of the transmission/reflection coefficients, variation of the phase between 0 and 2π) are linked to simple conditions on the positions of phase singularities in the complex-frequency plane. These positions are shown to be linked to certain symmetries of the metasurface. These findings provide a method for designing metasurfaces based on symmetry breaking.

The optimization of the quality factor (Q) of photonic resonators is of great importance for applications exploiting both ordered and disordered systems. Here we propose a gradient-based automated optimization approach to maximize the Q of optical resonances in ordered and disordered dielectric slabs which uses first-order non-hermitian perturbation theory. After benchmarking our method with an L3 photonic crystal cavity, we apply it to optimize a selected Anderson mode in a random design with initial Q-factor of 200, generating a new mode with Q = (10)^5.

We adopt a multi-objective optimization approach to design one-dimensional photonic crystals with large optical chirality enhancements. We show that this technique allows for a large design flexibility in terms of selected materials and operational wavelengths. Finally, we demonstrate that the designed platforms provide state of the art chirality enhancements above the two orders of magnitude over arbitrarily large areas and broad spectral ranges.

Ultrafast laser micromachining is a technological innovation with exciting potential for many applications and has led to impressive advances in the study of light-matter interactions. In this context, the laser-assisted wet etching fabrication technique has opened new frontiers in the optofluidic lab-on-a-chip, i.e. complex and easy-to-use microsystems capable of integrating multiple physicochemical processes on a single platform to replicate specific chemical, biological and medical tests typically performed in a laboratory. These miniaturised multifunctional laboratories exploit the synergy between the high sensitivity of optics and the unique ability to manipulate small quantities of microfluidics to develop a new frontier of analytical devices. The chips can be manufactured in monolithic 3D versions with no geometric constraints and are fully embedded in the substrate (typically fused silica). In addition to the advantage of using an inert substrate (strategic for biological applications), the elimination of the sealing step and the high mechanical strength offer numerous advantages. To demonstrate the potential of this new sensing platform, we report on the benefits of integrating in-plane 3D micro-optics to increase the S/N in-chip spectroscopic analysis in two case studies: flow cytometer devices and innovative chips for real-time Raman analysis of bio-samples in flow, even non-transparent ones.

Optothermal manipulation of small objects ranging in size from micrometers down to nanometers has demonstrated a high degree of control over particle motion through a combination of optical and thermal forces. Here, we show that long-range optofluidic flows can be induced via the absorption of light on plasmonic nanostructures creating localized hot spots. Through temporal and spatial light modulation, we can precisely engineer fluid flows by controlling the thermal landscape. We combine in-situ measurements of induced thermal fields using optical diffraction tomography (ODT) with 3D optical tracking of particles via off-axis digital holographic microscopy (DHM) allowing us to precisely monitor light induced environmental changes. With the help of simulations, we analyze the individual contributions stemming from the thermal and optical forces. This comprehensive toolbox allows us to design specific fluid patterns in 3D creating optofluidic boundaries and obstacles that steer particle motion. Alternating between different patterns of illumination over time creates various types of microfluidic actuators such as pumps, traps, and valves, all within a single chip environment. Our optofluidic approach provides an alternative pathway to develop multifunctional microfluidic chips for integrated sorting, detection, and analysis.

Motivated by the need for improved platforms in biomedical research, this study addresses challenges associated with traditional Ussing chamber systems, widely used in studying biological barriers like the epithelial barrier of the gut. These challenges include complexity, high sample volumes, and limited compatibility. By combining stereolithography and soft lithography techniques, a microfluidic Ussing chamber is manufactured, overcoming these limitations, and incorporating compatibility with microscopy. Validation through Trans-Epithelial Electrical Resistance (TEER) measurements confirms its efficacy in assessing ion permeability dynamics, utilizing Caco-2 cell monolayers. The study showcases the capability of the manufactured chamber for sensing impact of calcium on tight junctions.

Agriculture challenges to reduce its environmental impact and to improve control over agricultural crops of agriculture are numerous. We develop here an optical integrated probe as potential answer to some detection challenges, based on a RIB chalcogenide waveguide. Early results have shown that the fabrication process induces sidewall roughness potentially altering the sensitivity of the probe. The numerical tool used here implements an approximation allowing to take into account sidewall roughness on propagation losses. This code is based on finite element method. Results show that sidewall roughness have a higher impact on losses for narrow waveguides.

Carcinogenesis involves DNA methylation which is a primary alteration in DNA in the development of cancer before genetic mutation. Because the abnormal DNA methylation is found in most cancer cells, the assessment of DNA methylation using terahertz radiation can be a novel optical method to detect and control cancer. The methylation has been directly observed by terahertz time-domain spectroscopy and this epigenetic chemical change could be manipulated to the state of demethylation using resonant terahertz radiation. Demethylation of cancer cells is a key issue in epigenetic cancer therapy and our results demonstrate the feasibility of the cancer treatment using optical technique.

Controlled temperature elevation within biological tissues, known as hyperthermia, holds promise as a therapeutic treatment. Its efficacy depends on several factors including timing, pulsing, and repetition. Recent research indicates the potential of heat-based therapies not only for cancer treatment but also in tissue regeneration. The usage of photothermal agents, such as gold nanoparticles, enables precise spatio-temporal heat generation, known as photothermal therapy (PTT). Hydra vulgaris, with their unique regenerative capabilities, serve as valuable models for exploring the effects of nanoparticles on tissue regeneration. AuNPs thanks to their plasmonic properties can induce physiological responses in the animals under near-infrared (NIR) irradiation, ranging from cell ablation to programmed cell death or thermotolerance. By tuning the NIR irradiation and the AuNPs dose, the capability of treated polyps to regenerate the missing heads under photostimulation will be dissected, at whole animal, cellular and molecular levels and compared to exposure to external macroscopic heat sources.

Coronaviruses are characterized by spike (S) glycoproteins, which are the largest structural membrane proteins and the first involved in the anchoring of the host receptor angiotensin-converting enzyme 2 (ACE2) through the receptor binding domain (RBD). Its secondary structure is of great interest for shedding light on various aspects, from functionality to pathogenesis, finally to spectral fingerprint for the design of optical biosensors. The aim of this work is the characterization of the whole monomeric SARS-CoV-2 S protein, its constituting components, namely RBD, S1 and S2, at serological pH (7.4) and the S1 alterations induced to chemical/physical environmental modifications by measuring their amide I absorption bands through Attenuated Total Reflectance Infrared spectroscopy (ATR-IR).

Nature provides various organisms with ordered or quasi-ordered dielectric nanostructures that enable several animals, plants, and protists to manipulate light, optimizing inter- and intra-species communication, camouflage, or solar light harvesting. In particular, diatom microalgae possess nanostructured silica cell walls, known as frustules, which efficiently interact with optical radiation through multiple diffractive, refractive, scattering, waveguiding, and frequency down-conversion mechanisms. These properties contribute to diatoms’ efficiency in photosynthesis, UV tolerance, and possibly influence the phototaxis mechanisms of motile species. In our study, we utilized several imaging, spectroscopic, and numerical techniques to explore the optical functionalities of individual frustule components in the pennate, motile diatom Pleurosigma strigosum. We discuss the implications of frustule photonic properties on the living cell, and envision the exploitation of these properties in multifunctional, bio-derived photonic devices.

Thiophene-based materials (TMs) have emerged as promising candidates in the field of photodynamic therapy (PDT) as photosensitizers agents owing to their remarkable electron transport properties, which facilitate efficient energy transfer processes crucial for PDT. In detail, TMs exhibit favourable optical characteristics, making them suitable candidates for the absorption and conversion of light energy into reactive oxygen species (ROS), thereby inducing cytotoxic effects in targeted cells. Recent studies have explored natural carriers, including proteins and phages, for enhanced cell uptake and permeation of photosensitizers, thereby enabling the induction of apoptosis across various cell lines. Despite the remarkable potential of this approach for PDT purposes, clinical translation necessitates in vivo models to validate these innovative tools. Here, we investigated the nanosafety and in vivo efficacy of these phototheranostic agents using the tissue-like animal model Hydra vulgaris. The transparency, softness, structural simplicity, and ethical neutrality of Hydra collectively render it an exemplary model for such inquiries. These features facilitate rapid screening of cytotoxicity and the effectiveness for photodinamic purposes.

Bioresorbable photonic implants are emerging as potential material choice for interstitial theranostic and monitoring applications. They gradually dissolve within the physiological environment in a clinically relevant period, eliminating the need for extraction surgeries. In the present study, we tested the suitability of in-house fabricated bioresorbable optical fibres based on calcium phosphate (CaP) glass for diffuse correlation spectroscopic (DCS) and diffuse fluorescence tomographic (DFT) applications. The results represent the potential of bioresorbable fibers for the monitoring of interstitial microvascular blood flow and the spatial distribution of fluorescent photosensitizer drugs that are administered prior to therapies. Together or separate, the continuous monitoring of these parameters can have significant implications in planning, optimizing and in predicting or monitoring the outcomes in interstitial photodynamic therapy (PDT).

Zoom lens design can be particularly challenging because the aberrations of the lens groups change as the lens zooms. The changes of the third order aberrations of each lens group between the zoom configurations are related through stop and conjugate shift theory and can be quantified once the residual aberrations of the lens groups are known at just one zoom configuration. By applying stop and conjugate shift theory to examples from patent literature, we establish some basic principles of third order aberration balancing in zoom lenses design. These principles are then applied to existing designs and are used to guide a computational method for planning the aberration balance of a zoom lens.

Since the development of the first achromatic lenses back in the 18th century, dispersion models have been constant companions of optical designers. Usually glass properties are described by Abbe numbers and partial dispersions, and color correction is explained and visualized e.g. with Pg,F- and Herzberger diagrams. We have recently developed an alternative approach to color analysis and color correction based on principal component analysis (PCA) of normalized refractive index data. Unlike their traditional counterparts, the resulting diagrams can be used not only for glass selection, but also for a quantitative prediction of partial refractive powers and residual color aberrations, which arise naturally from the PCA. The method can easily be transferred to any spectral range and set of glasses, as it is intrinsically model-free and does not involve any choice of reference wavelengths or tuning of parameters. We present application examples of the method and discuss the impact of using different glass catalogs and wavelength samplings.

Mechanical and thermal disturbances in optical systems are attracting increasing attention as accuracy requirements rise. For this reason, it is necessary to consider these disturbances at an early stage in the design process. This can be done by a holistic multiphysical opto-thermo-mechanical simulation. Such an approach is presented with a focus on efficient thermomechanical computation through a quasi-static approximation.

A new approach for glass substitution in the lens system optimization process has been developed. Exploring existing longitudinal aberration contributions, the new method uses sensitivity analysis to find optimal optical glass constants (refractive index, Abbe number, and relative partial dispersion) for certain optical system elements. A case study introducing the glass substitution method to the optical system design is described. It is shown that the new approach provides step-by-step improvements in the optical system’s longitudinal aberration correction.

The high cost of optical raw materials in the long wavelength infrared (LWIR) region necessitates the development of cost-effective solutions without compromising resolution. Chalcogenide glasses offer a faster and easier production process compared to growing single crystals of Germanium (Ge). Additionally, they can be molded into complex optical surfaces, reducing processing costs further for serial production. In this study, we explore the potential of chalcogenide lenses. Our comprehensive design study demonstrates that chalcogenide lens designs can achieve comparable or even superior optical performance with reasonable system complexity when compared to a wide-angle benchmark Ge design.

Main objectives of RAVEN

Objective 1: Develop a VIS-SWIR gas sensor system composed of three chips. The first chip is a powerful, affordable, and compact supercontinuum light source designed for gas sensing. This chip aims to have minimal coupling loss and an overall power output of about 100 mW. It includes a high-peak microchip laser and a LiNbO3 waveguide operating in the 400-1700 nm range with a waveguiding loss of no more than 1 dB/cm. The second chip consists of gas sensing components designed to function in harsh environments. It features a double spiral waveguide for evanescent sensing, combined with a Bloch Surface Wave platform to detect gases within the 600-1700 nm spectral range. The third chip is a data processing chip that employs both standard and heterodyne interferometry on a SiO2 chip. This chip utilizes a hybrid polymer/TiO2 waveguide to enable on-chip data analysis using a quantum-inspired approach, improving the limit of detection and selectivity for various gases.

Objective 2: Develop a compact photoacoustic cell combined with a tunable MIR laser to create the MIR sensing system. This system will be capable of detecting gases like CO2, CO, CH4, NH3, and N2O, with a detection limit ranging from 1 to 10 parts per billion (ppb), depending on the gas.

Objective 3: Evaluate the VIS-SWIR and MIR sensors with end users in the laboratory under conditions simulating real-world environments for various applications, including monitoring greenhouse gases and air pollutants in terrestrial settings, quantifying dissolved methane in seawater for climate change impact studies and monitoring offshore pipeline leaks, and measuring concentrations of methane, methanol, and ammonia above surface waters for monitoring and researching episodic pollution events.

Environmental water pollution is a growing global issue, leading to increasing regulations and concurrent increased demand for improved water quality monitoring solutions to meet the European Green Deal objectives. To this end, IBAIA will design, develop and combine four innovative and complementary sensors for continuous water analysis: 1) a Mid-IR sensor detecting organic chemical pollutants, 2) a VIS-NIR sensor detecting salinity and microplastics, 3) an optode detecting physical- chemical parameters, and 4) an EC sensor detecting metallic trace elements (MTE) and nutrient salts (NS). These four sensors will be integrated and packaged into a single advanced multisensing system. The IBAIA system will more accurately monitor a wider range of parameters than existing solutions in a one-size-fits-all solution for many end users, with a highly EU-centric supply chain, that will supplant a wide number of inferior non-EU alternative solutions.

Miniaturized, yet highly sensitive and fast LiDAR systems serve market demands for their use on platforms ranging from robots, drones, and autonomous vehicles (cars, trains, boats, etc.) that are mostly used in complex environments. The widespread use of high-performance LiDAR tools faces a need for cost and size reduction. A key component of a LiDAR system is the light source. Very few lasers light sources exist that provide sufficient performance to achieve the required distance range, distance resolution and velocity accuracy of the emerging applications identified in LiDAR roadmaps. The available sources, namely single mode or multimode laser diodes and fiber lasers, are either very costly, not sufficiently robust or not compact enough. In OPHELLIA, we will investigate advanced materials and integration technologies directed to produce novel PIC building blocks, namely high gain, high output power (booster) amplifiers and on-chip isolators that are not yet available in a PIC format with the required performance. The novel building blocks will be monolithically integrated onto the Si3N4 generic photonic platform to produce high performance laser sources with unprecedented high coherence and high power, which will have a profound impact on the performance of the systems. Advanced packaging will further contribute to a dramatic reduction of the overall cost. To achieve this ambitious goal, OPHELLIA will leverage the expertise of its consortium members, ranging from materials, integration technologies and PIC design to packaging and LiDAR systems integration, which covers the full chain from innovation to the deployment of the technology in a relevant environment. The successful realization of OPHELLIA will not only represent a milestone towards the widespread utilization of LiDAR systems, but the developed building blocks will also have an enormous impact in other emerging application fields such as datacom/telecom, sensing/spectroscopy and quantum technology.

BIOCELLPHE provides frontier scientific and technological advancements to generate a breakthrough technology realizing the identification of proteins (i.e. phenotyping) as diagnostic biomarkers at single-cell level with unmatched sensitivity, multiplexing capabilities and portability. BIOCELLPHE proposes the generation of engineered bacteria able to recognize and bind to specific protein targets on the surface of circulating tumor cells (CTCs) responsible for cancer metastasis, thereby triggering the production of chemical signals that can be detected simultaneously, and with extremely high sensitivity by surface-enhanced Raman scattering (SERS). SERS is a powerful analytical technique that employs plasmonic nanoparticles as optical enhancers for ultrasensitive chemical analysis achieving single-molecule detection level. BIOCELLPHE will implement these advancements toward the generation of an optofluidic lab-on-a-chip SERS device enabling ultrasensitive identification and multiplex phenotyping of CTCs. We anticipate that BIOCELLPHE long-term vision and scientific breakthrough will lead to a sky limit technology that will be widely applicable, not only in the diagnostic arena, but also in many other applications (e.g. biomedical, environmental). No one has previously been able to attempt this vision due to current challenges and technical limitations, but we believe to be in a position to pave a way for achieving this now. To realize this highly ambitious project, BIOCELLPHE gathers a highly multidisciplinary community of leading experts in synthetic biology, nanotechnology, plasmonics, microfluidics, artificial intelligence, and cancer diagnosis. We believe that successful deployment of BIOCELLPHE has the potential to usher in a new era of medical diagnostics and it will provide new paradigms in biology and biomedicine, advancing frontier science and technologies at the European academic and industrial sectors.

The overall objective of the TinyBrains project is to build a unique platform that allows the non-invasive, three-dimensional imaging of cerebral hemodynamics and oxygen metabolism simultaneously with cerebral electrophysiology to understand the biological origins of brain damage that occurs in infants born with CHD.

The project is primarily dedicated for furthering scientific knowledge with the introduction of a new hybrid platform for neuromonitoring.

An optical neuroimaging device to understand the mechanisms of brain damage in infants born with severe CHD.

The EU-Horizon-2020 ISMarD project aims to develop a smart multifunctional tooth implant for providing a long-term solution for preventing the condition of peri-implantitis. Peri-implantitis is a dental implant-related inflammatory condition induced by oral bacteria. The lack of ossification of implant with surrounding bone and soft-tissue integration leave interstitial ingress of bacteria-laden oral fluid which increases lowers the pH around the implant-alveolar bone region. Increased acidity persistent acidity leads to bone resorption, increased pain and eventual failure of implant due to bone loss. In ISMarD, the project aims to design and manufacture infection resistant implants, that are able to ossify and integrate with soft-tissue after one-step surgery. The implants will be tested in vitro using two approaches – in the standard cell and microbial cultures and in micro-fluidic/opto-micro fluidic reactors before testing in vivo in minipig and beagle dog models. The programme of research and demonstration also aims to show the sustainable manufacturing by design for prolonging the implant lifetime and diagnostics.

Dual-comb spectroscopy combining key advantages of fast, broadband and accurate measurements has been established in the infrared as a method for the investigation of a variety of samples, more recently for the field studies of atmospheric gases with kilometer-scale absorption path lengths.

We could recently extend the application capabilities of field-deployed dual comb spectroscopy by developing a portable dual-comb spectrometer operating in the visible spectral region for atmospheric monitoring of NO2, a pollution gas of major importance. In combination with a multi-pass approach through the atmosphere, an interaction path length of almost a kilometer is reached while achieving both advanced spatial resolution (90 m) and high detection sensitivity (5 ppb).

By transposing DCS into the UV spectral region, the highly energetic UV photons can be exploited to drive electronic and rovibronic transitions in molecular (gas) species. We realized UV dual comb spectroscopy using two broadband ultraviolet frequency combs centered at 871 THz and covering a spectral bandwidth of 35.7 THz. We obtain rotational state-resolved absorption spectra of formaldehyde, a prototype molecule with high relevance for laser spectroscopy and environmental sciences in 100 µs of measurement time.

The experimental investigation of chemically and biologically relevant dynamics induced by visible or ultraviolet (UV) light requires high temporal resolution and spectroscopic techniques capable of resolving the complexity of these processes. Time-resolved photoelectron spectroscopy has proven to be a key tool for the study of these dynamics, but most studies have been conducted with a limited temporal resolution of about 100 fs. Furthermore, typical schemes employ a deep-UV probe, which limits the observation window and leads to spectrally congested traces. In this work, we present a UV pump – extreme-UV probe beamline with sub-20 fs temporal resolution, unambiguously characterized by an in-situ photoelectron cross-correlation measurement. As an example of the capability of the setup, we show a time-resolved investigation of the non-adiabatic dynamics of acetylacetone. The extreme temporal resolution allows us to resolve the passage through the first conical intersection and to identify the coherently excited vibrational modes.

Traditional amplifier-based pump-probe systems offer versatility but are often limited by their complexity and low measurement speeds, particularly when probing samples that require low excitation fluences and high sensitivities. To circumvent this limitation, we introduce a pump-probe system that leverages a novel 60 MHz single-cavity dual-comb oscillator and an ultra-low noise supercontinuum enabled by polarization maintaining all-normal dispersion fiber. The presented system can operate in equivalent time sampling mode (also known as asynchronous optical sampling) or in arbitrary optical delay generation mode. This dual-mode operation facilitates a broad range of time-resolved studies. We have employed this system to study the non-fullerene electron acceptor Y6, a compound of significant interest in solar cell development, revealing its response at various probe wavelengths with ultra-high sensitivity. The results demonstrate the system's potential to advance the field of ultrafast spectroscopy

We report an unexpected result of the anisotropy of the nonlinear optical response of carbon nanotubes, inherent to their chirality. Using a model based on the resolution of the semiconductor Bloch equations, we theoretically demonstrate that, upon irradiation with an intense linearly polarized laser pulse along the axial direction, chiral nanotubes exhibit an oscillating azimuthal current that is absent in achiral species. This current induces a magnetic field parallel to the axis of the nanotube that radiates like a loop antenna.

ADASOPS pump-probe spectroscopy is a multi-timescale technique that is spreading rapidly especially in the field of biomolecule dynamics. Based on slight variations of the laser repetition rate, it is simple to implement and can cover a time range extending from a hundred femtoseconds to a millisecond or more. We have studied the energy fluctuations associated with this approach and have proposed a method for overcoming any instabilities.

Optical frequency comb based on microresonator (microcomb) is an integrated coherent light source

thanks to its high integrity, low power consumption, and low phase noise. Especially, octave spanning

microcombs via dispersion engineering can realize a chip-scale 2f-3f or f-2f self-referencing scheme and

has the potential to promise a high-precision frequency standard. In practice, the stability of the soliton

comb source is the basis of subsequent signal processing. However, achieving a long-term stable soliton

comb can be challenging due to thermal effects or center frequency jitter induced by the pump. This often

requires a complex feedback system, which hinders the minimization of the device.

Domain reversal engineering stands out as an essential procedure for realizing effective nonlinear conversion on periodically poled lithium niobate on insulator (PPLNOI), laying a promising foundation for nonlinear photonic integrated circuits (PICs). However, the domain reversal for thin-film lithium niobate has been confined to the chip scale, hindering its use in extensive nonlinear photonic systems. Here, we present a wafer-scale periodic poling platform on a 4-inch LNOI wafer, covering reversal lengths from 0.5 to 10.17mm and periods ranging from 4.38 to 5.51 μm with high fidelity. The efficient poling is enabled by a single operation over ~1 cm^2 area, using strategically grouped electrode pads and adjustable comb line widths. We achieved a 100% success rate and a 98% high-quality rate on average, showcasing high throughput, stability and scalability, making it more economically viable than chiplet-level poling. Our research holds immense potential to significantly enhance ultra-high performance for applications in optical communications, photonic neural networks, and quantum photonics.

We reported structured NIR dual-optical parametric oscillators (OPOs) and tri-wavelengths yellow-orange beams from a monolithic periodically poled lithium tantalate. The structured dual-OPOs comprise of dual-signal wavelength at 980 and 964 nm, which are residing on the opposite sides of TEM10 cavity mode. By introducing additional up-conversion processes, a structured tri-wavelength yellow-orange TEM20 cavity mode can be observed. We consider a numerical model by including a Laplacian operator in the transverse plane to simulate the distribution of dual OPO. Our calculation indicates that the structured mode was attributed to the transversally inhomogeneous nonlinear optical gain.

Optical damage resistant ridge waveguides for blue and near UV wavelengths have been fabricated using high-temperature Zr and Zn diffusion doping and vapor transport equilibration (VTE) of congruent LiTaO3 crystals. For both dopants high optical damage thresholds >10 MW/cm2 for 532 nm light were demonstrated at room temperature, which can be increased by a factor ~3 when heating the samples to ~150°C. Ridge waveguides with low optical losses of ~0.4 dB/cm were fabricated using diamond-blade dicing. First-order periodic poling with grating periods of ~3 um can be used for efficient nonlinear frequency conversion for both SHG (800 nm pump) or SPDC (400 nm pump) processes.

The aim of the PhD project is to develop a new trend in modulation system for Exail company: thin film (<1 µm) lithium niobate (LN) electro-optic modulator. It exhibits better performance in term of bandwidth, power consumption and footprint than legacy ones [1-3]. This PhD is a cooperation between Exail photonics which is world-renowned for the performances of their electro-optic modulators and FEMTO-ST institute which can offer the possibility to grow stoichiometric LN thin film by means of direct liquid injection metalorganic chemical vapor deposition (DLI-MOCVD). This cooperation opens the possibility to obtain industrialization of optical device based on CVD LN stoichiometric layers which allow to have enhanced performances such as higher electro-optic coefficient than that of congruent compositions of commercial single crystals. Thus, all steps from MOCVD layer deposition to modulator realization can be done here in Besançon

The progression of fibrosis is frequently related to a failed healing process, and it may affect many tissues and organs causing severe consequences including post-infarct heart insufficiency, post-injury limb paralysis, cirrhosis, nephropathy, retinopathy, failure of implanted devices and even resistance to chemotherapy in solid tumours. Experimental models, both in vitro and in vivo, are widely used for studies of basic pathophysiology, and for pre-clinical testing of pharmacological therapies counteracting fibrosis. However, conventional models are not able to realistically reproduce the revascularization aspect of the inflammatory reaction that leads to the generation of fibrotic tissue. In this talk, I will present the most advanced frontier in this sector, represented by the new concept of an "organism-on-a-chip". This is a hybrid model, in which an organ-on-a-chip is implanted sub-cute in a living organism, such as a mouse or an embryonated avian egg, thus eliciting a foreign-body reaction with the formation of a fibrotic microenvironment. In an organism-on-a-chip, the fibrotic reaction can be guided in terms of extra-cellular stiffness and vascularity, using microscopic scaffolds incorporated in the implanted chip. The fibrotic microenvironment can then be imaged longitudinally, in high resolution, with the added advantage of significantly reducing animal sacrifice.

We present how to develop virtual microcylinder- or microsphere-assisted surface topography measurement instruments. As the most critical part, the interaction between light, microcylinder and measurement object is considered based on the finite element method (FEM). Results are obtained for microcylinder-assisted conventional, interference, and confocal microscopes without necessity to repeat the time-consuming FEM simulations for each sensor.

Topographical as well as microscopic imaging of nanoscale surfaces plays a pivotal role across various disciplines. Nevertheless, achieving fast, label-free, and accurate characterization of laterally expanded structures below the diffraction limit remains challenging. Recent studies highlight the use of microsphere assistance for resolution improvement. Confocal microscopy, augmented by microspheres, enables the imaging of small structures that were previously inaccessible. This is experimentally compared with microsphere-assisted microscopy (MAM) to underline the decisive role of the confocal effect.

Nearfield spectroscopy is crucial for characterizing micro- and nanostructures and it often requires hyperspectral imaging, where at each spatial point a full spectrum is recorded. Due to its combination with an atomic force microscope, nearfield hyperspectral imaging is serial in nature and results in long acquisition times and stability challenges, also restricting its industrial use. In this work, we employ a subsampling strategy combined with low-rank matrix reconstruction in a commercial nearfield spectroscopy system to significantly shorten measurement acquisition times.

Optical vortices, characterized by their helical phase topology and ability to carry orbital angular momentum, have found diverse applications in metrology. In this work, we present novel metrology systems utilizing vortex beams. The adaptation of optical vortex microscopy for rough surface measurement using fluorescent nanomarkers, and experimental setup for retardation measurement are described. Retardation measurement has been successfully applied to the calibration of spatial light modulator and can be adapted for measurement of circular dichroism. In developed methods the information on retardation or local surface height is restored from self-interference spread function of optical vortex beams carrying opposite topological charges, called Double-Helix Point Spread Function (DH PSF). The use of neural networks, enhancing measurement accuracy and enabling advanced data analysis for data processing, is described.

Hybrid photonic devices, harnessing the advantages of multiple materials while mitigating their respective weaknesses, represent a promising solution to the effective on-chip integration of generation and manipulation of non-classical states of light encoding quantum information. We demonstrate a hybrid III-V/Silicon quantum photonic device combining the strong second-order nonlinearity and compliance with electrical pumping of the III-V semiconductor platform with the high maturity and CMOS compatibility of the silicon photonic platform. Our device embeds the spontaneous parametric down-conversion (SPDC) of photon pairs into an AlGaAs source and their subsequent routing to a silicon-on-insulator circuitry. This enables the on-chip generation of broadband telecom photon pairs by type 0 and type 2 SPDC from the hybrid device, at room temperature and with strong rejection of the pump beam. Two-photon interference with 92% visibility proves the high energy-time entanglement quality characterizing the produced quantum state, thereby enabling a wide range of quantum information applications.

Nonlocal correlations exhibited by quantum systems are fundamental for secure remote quantum information tasks and tests of fundamental quantum physics. Bell nonlocality is highly susceptible to noise, which degrades the quality of nonlocal correlations, leading to the existence of Bell local states. These mixed entangled states cannot display nonlocality in a standard Bell scenario. Here we experimentally demonstrate that single copies of Bell local states can demonstrate nonlocal behavior when integrated into a multi-partite photonic network.

Molecular polaritons are hybrid light-matter states that emerge when a molecular transition strongly interacts with photons in a resonator. At optical frequencies, this interaction unlocks a way to explore and control new chemical phenomena at the nanoscale. Achieving such control at ultrafast timescales, however, is an outstanding challenge, as it requires a deep understanding of the dynamics of the collectively coupled molecular excitation and the light modes. Here, we investigate the dynamics of collective polariton states, realized by coupling molecular photoswitches to optically anisotropic plasmonic nanoantennas. Pump-probe experiments reveal an ultrafast collapse of polaritons to pure molecular transition triggered by femtosecond-pulse excitation at room temperature. Through a synergistic combination of experiments and quantum mechanical modelling, we show that the response of the system is governed by intramolecular dynamics, occurring one order of magnitude faster with respect to the uncoupled excited molecule relaxation to the ground state.

In quantum mechanics, the precision achieved in parameter estimation using a quantum state as a probe is determined by the measurement strategy employed. The quantum precision limit, a fundamental boundary, is defined by the intrinsic characteristics of the state and its dynamics. Theoretical results have revealed that in interference measurements with two possible outcomes, like the Hong Ou-Mandel interference, this limit can be reached under ideal conditions of perfect visibility and zero losses. However, this cannot be achieved in practice, so precision never reaches the quantum limit. But how do experimental setups approach precision limits under realistic circumstances?

In this work, we provide a general model for precision limits in two-photon Hong-Ou-Mandel interferometry for non-perfect visibility and validate it experimentally using different quantum states. A remarkable ratio of 0.97 between the experimental precision and the quantum limit is observed, establishing a new benchmark in the field.

Photonic integrated circuits (PICs) based on silicon-on-insulator (SOI) substrates provide a lightweight, compact platform for applications in quantum optics. We show the evaluation and characterization of an SOI-based PIC design for an entangled photon pair source, generating photon pairs by means of the nonlinear process of spontaneous four-wave mixing in microring resonators. Experimental results following from the chip fabrication fed back into the simulated parameter tuning effects, culminating in photon pair generation with measured correlations exceeding classically predicted limits.

Photonic Orbital Angular Momentum (OAM) is becoming a pertinent quantum variable for atom-light interaction, in particular for non-linear interaction which leads to photon entanglement and OAM-entanglement. With two 4-levels atomic schemes, we show that Four Wave Mixing addressed by vortex beams leads to very different OAM-entanglement especially for large OAM values.

We theoretically show that under circularly polarized plane wave or vortex beam illumination, the second-harmonic circular dichroism is possible even if the nanostructure is achiral. The interplay of nanostructure's and crystalline lattice's symmetries leads to specific conditions for observation of the circular dichroism, which can be expressed by a short formula. This can be particularly important for chiral sensing enhancement with nanostructure, where it is important to separate the signal from the nanostructure itself.

In recent years a strong drive towards the miniaturization of nonlinear optics has been motivated by the functionalities it could empower in integrated devices. Among these, the upconversion of near-infrared photons to the visible and their manipulation is fundamental to downsize optical information. We realized a dual-beam scheme whereby a pulse at the telecom frequency ω (λ=1550 nm) is mixed with its frequency-doubled replica at 2ω. When the two pulses are superimposed on a nonlinear, all-dielectric metasurface two coherent frequency-tripling pathways are excited: third-harmonic generation (THG, ω+ω+ω) and sum-frequency generation (SFG, ω+2ω). Their coherent superposition at 3ω produces interference, which we enable by filtering the k-space with the metasurface diffraction. The emission routing among diffraction orders is sensitive to the relative phase between the two pumps. Therefore, by exploiting the phase difference as a control mechanism, the upconverted signal can be commuted between diffraction orders, with measured visibility >90%. The proposed approach can be envisioned as an all-optical method to route upconverted telecom photons.

Lattice resonances (LR), collective electromagnetic modes supported by periodic arrays of metallic nanostructures, produce very strong and spectrally narrow optical responses. Usually, they arise from the coherent interaction between the localized electric dipolar plasmonic modes of the individual constituents of the array. Unfortunately, a two-dimensional arrangement of electric dipoles cannot absorb more than half the incident power due to fundamental symmetry reasons, thus hindering the use of LRs for applications requiring an efficient absorption of light. In this communication, we report a novel approach to overcome this constraint, which is based on the use of an array made of a unit cell containing one metallic and one dielectric nanostructure. Using a rigorous coupled dipole model, we show that this system can support two independent LRs, one with magnetic and the other with electric dipolar character, whose properties are tuned independently by adjusting the periodicity of the array and the size of the nanostructures. Furthermore, we show that an appropriate choice of these parameters not only leads to perfect absorption but also to quality factors exceeding 10^3. This work provides a general framework to design and implement complex 2D arrays capable of sustaining LRs with perfect absorption.

Photonic crystal slabs (or patterned multilayer waveguides) are known to support truly guided modes with no losses, as well as quasi-guided modes that lie in the continuum of far-field radiation. In this contribution, we present a guided-mode expansion approach – and the corresponding free software named “legume” – that allows calculating a number of features of quasi-guided modes of photonic crystal slabs: (a) symmetry properties and the issue of polarization mixing in coupling to far-field radiation modes; (b) the occurence of bound states in a continuum, which have infinite Q-factor and give rise to topological singularities of the far-field polarization; (c) the description of active two-dimensional layers through a suitably formulated light-matter coupling Hamiltonian, allowing to describe the regime of strong coupling leading to photonic crystal polaritons. Comparison with rigorous coupled-wave analysis, and the insurgence of non-hermitian features in the optical properties, are also addressed.

We report the fabrication and validation of an experimental system that exploits plasmonic Au nanoparticles to generate heat on a nanometric lateral scale, and measures the local temperature increase in the surroundings of these nanoparticles by means of carefully placed monolayers of transition metal dichalcogenide (TMDC).

Despite significant progress in the detection of small microplastics, the detection of such particles still faces problems caused by the limitations of current detection methods. We introduce optical methods for the analysis of individual microplastics and the fabrication of a substrate using plasmonic particles to detect plastic nanoparticles. We summarize recent experimental activities involving the construction of portable Raman tweezers that can be used for analysis of microsplastics. Optical trapping is complemented by nanoimprinting of plasmonics nanoparticles that enables create the "active" aggregates that can be used for Surface Enhanced Raman Spectroscopy (SERS) detection and as plasmon-enhanced thermoplasmonic concentrators for nanoscale plastics. The principle of nanoimprinting is based on the dominance of the scattering force (compared to the gradient force) for plasmonic particles, this force pushes particles in the direction of propagation of the light beam. In both cases, enhanced sensitivity is demonstrated, allowing the detection of nanoplastics of size orders of magnitude lower than what can be achieved by Raman spectroscopy. This study demonstrates that the combination of two optical manipulation techniques are capable of filling the technological gap in the detection of plastic particles ranging in size from a few tens of nm to 20 µm.

Hepatocellular carcinoma (HCC), the most common form of primary liver cancer, represents a global health challenge due to its complexity and the limitations of current diagnostic techniques. By combining Raman spectroscopy and Artificial Intelligence (AI), we have succeeded in classifying tumor cells. In fact, we have performed a first Raman spectral analysis based on the characterization and differentiation between uncultured primary human liver cells derived from resected HCC tumor tissue and the adjacent non-tumor counterpart. Biochemical analysis of the collected Raman spectra revealed that there is more DNA in the nuclei of the tumor cells than in non-tumor cells. We then develop three machine learning approaches, including multivariate models and neural networks, to rapidly automate the recognition and classification of the Raman spectra of both cells. To evaluate the performance of the developed AI models, we prepared and analyzed two additional cell samples with a ratio of 4:1 and 3:1 between tumor and non-tumor cells and compared the obtained results with the nominal percentages (accuracy of 80 and 60%, respectively). These results confirm that the models are able to make classifications at the level of a single spectrum, indicating the possibility of rapidly analysing and classifying a primary HCC cell.

Metastasis stands as the leading cause of mortality among colorectal cancer (CRC) patients. Galunisertib (LY2157299, LY) is a small molecule demonstrating promising anti-cancer effects by targeting the Transforming Growth Factor-beta (TGF-β) pathway. This route plays a pivotal role in initiating the epithelial-to-mesenchymal transition (EMT), a critical process for metastatic spread. Unfortunately, LY chronic treatment causes undesired effects. To mitigate these side effects, nanoscale drug delivery systems have emerged as a transformative approach in cancer treatment, enhancing drug effectiveness while minimizing toxicity. In this study, we introduce a hybrid nanosystem (DNP-AuNPs-LY@Gel) comprising porous diatomite nanoparticles decorated with plasmonic gold nanoparticles (AuNPs), encapsulating LY within a gelatin shell. This multifunctional nanosystem demonstrates efficient LY delivery, EMT reversal in CRC 2D and 3D cultures, and anti-cancer effects in vivo. Moreover, the nanosystem allowed the quantification with sub-femtogram resolution of the drug intracellularly released using surface-enhanced Raman spectroscopy (SERS). The release of LY is triggered by CRC cell acidic microenvironment. Real-time monitoring of drug release at the single-cell level is achieved by analyzing SERS signals of LY within CRC cells. The heightened efficacy of LY delivery through the DNP-AuNPs-LY@Gel complex offers a promising alternative strategy for reducing drug dosages and subsequent undesired effects.

The presence of microplastics in various food products has raised significant concerns regarding potential health risks for consumers. Among these products, milk, being a staple in many diets, has attracted attention for its widespread consumption and nutritional significance. In this work, a metrological method was developed to accurately quantify and characterize small microplastics (100-5 μm) in milk powder (infant formula) using micro-Raman (μRaman) technology, combining enzymatic digestion, organic matter removal under alkaline conditions, chemical analysis, microwave digestion and a final filtration step through a silicon (Si) filter. The present methodology was developed and validated for several polymers using both commercially available reference materials with defined dimensions and morphology, and more representative polydisperse materials.

Regarding PET microplastics, size, number and numerical distribution were previously evaluated in an intervalidation study involving two different laboratories with different micro-Raman instrumentation to provide a reference number for this material. The analytical procedure was further validated in terms of microplastic recovery rate and quantification sensitivity with the calculation of LOD (limit of detection) and LOQ (limit of quantification)

Additives are excessively used in agriculture for the purposes of crop protection, and enhancement of the yield quality and quantity of the products. Although the use of these chemicals is necessary for the food industry, they are associated with short- and long-term effects on human health. Thus, their use should be regulated, and their detection is critical not only for human health but also for the environment and wildlife. In this study, the detection of additives by surface-enhanced Raman scattering (SERS) substrates is proposed. For this purpose, flexible substrates are prepared from poly(ethylene glycol) diacrylate (PEGDA) and gold Nanoparticles (AuNPs). The detection performance of the designed substrates was tested against sulfur dioxide (SO2). It was found that designed substrates can provide homogenous signal distribution and significant signal enhancement. Moreover, they can allow detection of SO2 in wine down to 0.4 ppm which is lower than the regulatory limits.

Single-cell analysis without immune-specific labelling is essential across research fields, but conventional flow cytometers (FCMs) struggle with label-free analysis. We introduce a novel microfluidic scanning flow cytometer (µSFC) designed for label-free analysis within a simple microfluidic chip. Our system outperforms traditional FCMs for label-free analysis but its signal-to-noise ratio (SNR) limits the minimum detectable size. We present three modifications to enhance SNR and improve the smallest detectable particle size: additional neutral optical density filtering, a lower noise-equivalent-power photoreceiver, and laser spot size reduction. These improvements enable reliable characterization of particles as small as 3 µm. Experimental results validate the correlation between angular profile oscillations and particle size. While reliable detection down to 1 µm is achieved, further refinement is needed. The simplicity and low setup of the µSFC make it promising for integration into multi-parametric single-cell analysis systems, facilitating comprehensive cellular characterization for diagnostic and point-of-care applications.

Imaging flow cytometry (IFC) integrates flow cytometry with optical microscopy, enabling high-throughput, multi-parameter analysis of single cells. Current 3D IFC systems face limitations related to instrumental complexity that might lead to optical misalignment or mechanical instabilities in day-by-day operation. We propose a fully integrated optofluidic platform combining reconfigurable photonic circuits and cylindrical hollow lenses for structured light sheet microscopy in a microfluidic channel. The components are fabricated using femtosecond laser irradiation and chemical etching, ensuring a high level of integration that allows durable alignment and mechanical stability.

Statistical analysis of properties of single microparticles, such as cells, bacteria or plastic slivers, has attracted increasing interest in recent years. In this field flow cytometry is considered the gold standard technique, but commercially available instruments are bulky, expensive, and not suitable for use in Point-of-Care (PoC) testing. Microfluidic flow cytometers, on the other hand, are small, cheap and can be used for on-site analysis. However, in order to detect small particles, they require complex geometries and the aid of external optical components. To overcome these limitations here we present an opto-fluidic flow cytometer with an integrated 3D in-plane spherical mirror for enhanced optical signal collection. As result the signal-to-noise ratio is increased by a factor of 6, enabling the detection of particle sizes down to 1.5µm. The proposed optofluidic detection scheme allows the simultaneous collection of particles fluorescence and scattering - using a single optical fiber - which is crucial to easily distinguish particle populations with different optical properties. The devices have been fully characterized using fluorescent polystyrene beads of different sizes. As a proof of concept for potential real-world applications, signals from fluorescent HEK cells and Escherichia coli bacteria were analyzed.

This project aims to produce a microfluidic device capable of separating 6 µm and 20 µm diameters particles by inertial sorting. This Lab-on-Chip (LoC) was designed with a trapezoidal cross-section for better fluid control and effective particle manipulation at the microscopic level, as demonstrated by COMSOL simulations. The device was manufactured on a substrate of Polymethyl Methacrylate (PMMA) by femtosecond laser technology and then assembled using an innovative geometry-preserving Isopropyl alcohol-based procedure. The LoC was test with spherical plastic microparticles of two diameters (6 µm and 20 µm) suspended in distilled water. The separation efficiencies were (98.2 ± 1.6) % for 20 µm diameter particles and (70.0 ± 1.8) % for 6 µm diameter particles in good agreement with the simulation results. Finally, after a microfluidic channels’ acetone vapors treatment, the device demonstrated a good ability to separate biological particles (Red Blood Cells) at different concentrations (20%, 30%, 40%, 50%) in a PBS buffer.

Pancreatic ductal adenocarcinoma (PDAC) is a prevalent form of pancreatic cancer, contributing significantly to cancer-related mortality worldwide. Early lesions manifest within the exocrine pancreatic gland. Thus, in vitro fully human models of the exocrine pancreatic unit are needed to foster the development of more effective diagnosis and treatments. However, it is challenging to make these models anatomically and functionally relevant. Here, tomographic volumetric bioprinting was used to biofabricate human fibroblast-laden gelatin methacrylate-based pancreatic models, mimicking glandular structure. Indeed, this technique is an optically based method that uses reverse optical tomography to construct 3D objects in a layerless fashion.

Pancreatic epithelial cells, healthy or cancerous, were then seeded, and the development of a thin epithelium inside the lumen of the 3D model was demonstrated. Immunofluorescence and ELISA assays revealed higher activation of fibroblasts when they were co-cultured with cancer cells, replicating the realistic situation in vivo. To our knowledge, this is the first demonstration of a 3D bioprinted portion of pancreas that recapitulates its physiological 3-dimensional microanatomy, and which shows tumor triggered inflammation. It opens new avenues to the application of light-based additive manufacturing in tissue engineering, overcoming the difficulties associated with light scattering from cells in hydrogels.

Non-linear excitation microscopy offers superior in-vivo imaging but faces challenges in deep tissue. High numerical aperture beams suffer spherical aberrations, while tissue scattering impacts image quality. To address this, we propose implantable microlenses for precise focusing below the skin in lab animals. By using low numerical aperture lasers, we avoid spherical aberrations induced by high NA objectives. Our study presents various microlens designs differing in size, shape, and fabrication methods, all on glass or organo-hybrid ceramic substrates. This approach shows promise for enhancing deep tissue imaging, facilitating better understanding of biological processes in vivo.

Computer scientists discovered that a school of Italian landscape painters in the 18th century around Giovanni Paolo Panini (1691 - 1765) did not paint their paintings in rectilinear perspective, but in an alternative, non-rotationally symmetrical perspective projection. For three-dimensional landscapes with large fields of view, Panini’s projection provides much better images. Recently, it has been widely used in 3D computer graphics software and game engines. However, this alternative perspective projection is still unknown in the optics community.

We present first optical designs of imaging systems with Panini projection. The use of toric or free-form surfaces is very advantageous for this type of system. We discuss the pros and cons of hardware and digital post-processing solutions as well as a design example that benefits from a digital co-optimization strategy.

Analytical expressions for the ray-transfer matrix have been proven useful for the understanding of ray propagation in gradient-index (GRIN) lenses. The determination of an exact analytical expression for the ray-transfer matrix of arbitrary GRIN lenses remains unsolved. We propose an approximation based on the perturbation method with highly accurate results for models of the crystalline lens, which outperforms existing methods.

The fast computation of the Jacobian is an essential part in the optimization of optical systems using the damped least-squares algorithm. While finite differences provide an intuitive way to approximate derivatives, algorithmic differentiation is a technique to calculate them exactly. However, applying algorithmic differentiation to a raytracing routine for optical systems with many parameters is comparatively expensive, where the main costs are caused by the determination of a ray-surface intersection. To overcome this disadvantage, we present a mathematical analysis of the ray-surface intersection and its efficient differentiation in both forward and reverse mode algorithmic differentiation. Futhermore, the structure of the optimization variables and operands is exploited to derive a method that allows to compute the Jacobian in the same order of computational complexity as the primal raytrace. The method is successfully tested for a freeform design task and a classical spherical lens system.

OptiMat, by Sagittal Optics, is a tool developed to generate initial designs for color-corrected lens-based systems. OptiMat focuses on material selection, which is the most critical aspect for correcting chromatic aberration. However, this tool extends beyond material selection; it is also used to establish initial systems in the design process, which optical designers can further refine. By selecting from a catalog of materials and specifying the number of lenses in the system, optical designers receive the ideal combination of materials to correct chromatic aberration, together with a set of parameters to further improve the received system, such as lens ordering and radii. Additionally, engineers can filter combinations based on different metrics, such as chromatic and monochromatic aberrations.

In optical system design, material selection is not usually decided at the start of the project. Instead, it is determined gradually through a merit function that explores numerous combinations, which is an inefficient method. OptiMat identifies the best material combination upfront, drastically reducing design times from months to hours.

In this contribution, the results achieved through OptiMat will be presented alongside case study outcomes and detailed comparisons with other tools. This will highlight the significant advantages offered by OptiMat in optimizing lens-based systems.

Accurate and uniform fabrication of microstructures on highly curved substrates requires exposure with the waist of a focused laser beam at every point. In order to realize this, the exposure beam must be held perpendicular and focused onto the local substrate. Here we present an optical tool for our developed 5-axis nano-positioning and nano-measurement machine based on the chromatic differential confocal microscope.

Nonlinear optics lies at the heart of classical and quantum light generation. The invention of periodic poling revolutionized nonlinear optics and its commercial applications by enabling robust quasi-phase-matching in crystals such as lithium niobate. However, reaching useful frequency conversion efficiencies requires macroscopic dimensions, effectively limiting on-chip integration with ultracompact footprints.

Here we realize a periodically poled van der Waals semiconductor (3R-MoS2). Due to its exceptional nonlinearity, we achieve macroscopic frequency conversion efficiency (0.01%-0.1%) over a microscopic thickness of only 3μm, 10−100× thinner than current systems with similar performances.

Further, we report the generation of photon pairs at telecom wavelengths via quasi-phase-matched spontaneous parametric down-conversion. This work opens the new and unexplored field of phase-matched nonlinear optics with microscopic van der Waals crystals, unlocking new applications that require simple, ultracompact technologies such as on-chip entangled photon-pair sources for integrated quantum circuitry and sensing.

Multi-pass cells, known for their efficient spectral broadening, currently face a challenge in their peak power scalability. To address this, we implemented a strategy where the input pulse was split into 8 replicas, resulting in an increased pulse energy following nonlinear compression. The used laser delivered 208 fs pulses at 1030 nm, with pulse energies reaching up to 140uJ. Using 3 calcite crystals, the input pulse was divided and passed through the MPC, achieving a spectral broadening down to a 40 fs bandwidth limit. Subsequently, the replicas were recombined using an identical set of crystals and compressed via chirped mirrors. FROG measurements revealed a duration of 43 fs. The recombination losses amounted to less than 5 % of the output energy. This method is particularly attractive and cost-effective for spectral broadening of ultrafast lasers with adjustable repetition rate.

We present a single-stage nonlinear compression of a high power, high repetition rate Yb-doped amplifier based on a gas-filled multi-pass cell (MPC). The amplifiers delivers 100 W, 570 fs pulses at 1030 nm.

At the output of the 6.15 bar Ar-filled MPC, we measure 91 W, 22.4 fs corresponding to a transmission higher than 90 % and a compression factor of 26.

In the last years, differentmethods of laser pulse post-compression have proven their efficiency. Nonlinear spectral broadening achieved when coupling an ultrafast pulse in a gas-filled multi-pass-cell (MPC) provides common pulse compression factors of 10 to 20, depending on the initial pulse duration. We report here on the compression of up to 2 mJ, 330 fs pulses of an Ytterbium (Yb) laser down to sub-20 fs (compression factor of 17), using gas-filled MPCs, at the limit of temporal pulse breakup. Numerical calculations reproducing the experiment data, and demonstrating the importance of the driver pulse profile on the shape of the broadened spectra, are discussed.

Analysis of defects in optical materials is crucial for their applicability in cutting-edge optical components. Since calcium fluoride (CaF2) is highly regarded for optical applications, understanding the nature of defects within CaF2 is particularly significant. These defects have been conventionally identified through absorption and photoluminescence (PL) emission studies. In this work, we investigate the defects by measuring laser-induced fluorescence (LIF) spectra over a long irradiation. By decomposing the PL spectrum into multiple Gaussian PL bands, we identify the defects within the CaF2 material. The measurement of irradiation-induced PL can be rationalized by the stabilization of F-centers via the formation of M-centers. PL mapping has been also studied to study the potential link between the surface oxygen contamination of CaF2 samples and polishing techniques.

Metal-Organic Frameworks (MOFs) have emerged as promising candidates for detecting metal ions owing to their large surface area, customizable porosity, and diverse functionalities. In recent years, there has been a surge in research focused on MOFs with luminescent properties. These frameworks are constructed through coordinated bonding between metal ions and multi-dentate ligands, resulting in inherent fluorescent structures. Their luminescent behavior is influenced by factors like structural composition, surface morphology, pore volume, and interactions with target analytes, particularly metal ions. This study investigates the impact of Fe3+ cation exchange on the structural, thermal, and photoluminescent (PL) properties of MIL-53(Al) MOF samples. Incorporating Fe3+ ions induces structural distortions, altering coordination environments and leading to amorphization. Enhanced metal-ligand bonds boost thermal stability, delaying decomposition processes. Raman peak changes reflect ionic and charge disparities, disorder from cation exchange, and electronic effects. PL emission spectra variations reveal MOF framework influence on emission characteristics, with Fe3+ exchange quenching PL intensity and shortening lifetimes due to structural distortions and stronger linker binding, favoring non-radiative decay. These findings underscore the complexity of MOF interactions, crucial for applications like catalysis, gas storage, and luminescent devices. Cation exchange emerges as a promising strategy for tailoring MOF properties to specific needs.

3D-hollow microstructures with few tens of micrometer in diameter and up to 330 µm in length with an optical-quality surface roughness (Ra ≤ 1 nm) have been fabricated in the volume of lithium niobate by selective etching of fs-laser written structures and post-etching annealing. The fs-laser writing parameters and the annealing process have been refined to reduce the average surface roughness and the shape change. Systematically investigating the annealing process, a functional description of the temporal evolution of the surface roughness was found completing the data set of processing parameters for selective etching of fs-laser written structures, allowing to control the fabrication process of the hollow microstructures concerning both shape and surface roughness precisely. Thus, our results represent another milestone within the research towards monolithic micro-(opto)fluidic applications inside the multifunctional crystal lithium niobate.

Planar X-cut lithium niobate (X-LiNbO3) optical waveguides were prepared by proton exchange in benzoic acid. We carried out Raman spectroscopy of proton exchange (PE) and annealing proton exchange (APE) in the cross-section of the substrate. The E(TO1) mode after annealing indicates compositional disorder near the surface, while it is not visible by Raman before annealing. In order to isolate the PE film, undercut has been performed by focused ion beam (FIB). The isolated film presents no more ETO1 but spectra characteristic of LiNb3O8. Ab-initio calculations confirm stable proton exchange layers of HNbO3. The focused ion beam seems to have activated the cubic phase of HNbO3 to monoclinic LiNb3O8. Rhombohedra LiNbO3, cubic HNbO3 and monoclinic LiNb3O8 transform coherently.

Vanadium dioxide has attracted much interest due to the drastic modification of the electrical and optical properties it undergoes following the transition from the semiconductor to the metallic state, which takes place at a critical temperature of about 68°C. Many advanced fabrication methodologies have been proposed to improve the performance of VO2 thin films for phase-change applications in optical devices. Here, a purely optical approach is proposed, combining Phase-Transition by Continuous Wave Optical Excitation and Polarized Raman Mapping to acquire both morphological and thermal behaviour information of pulsed laser deposited polycrystalline VO2 thin films. The combination of the two techniques allows to reconstruct a complete picture of the properties of the samples in a fast and effective manner, for comparison and optimization purposes, but also to unveil an interesting stepped structure of the hysteresis cycles.

There has been an unprecedented increase in the growth of photonic components over the last 25 years based on different photonic materials; each having structural/functional limitation in integrated devices.

The challenge is that the semiconductors are grown inside MBE chambers, whereas the polymeric waveguides are fabricated by spin-coating. By comparison, glass and crystal-based materials are processed via sputtering and sol-gel techniques. None of these materials processing techniques, therefore, are compatible for a single-step device fabrication, due to the incompatibilities of chemical and physical properties of individual materials. A solution for overcoming the materials limitation is to develop a multi-materials deposition chamber which allows sequential/heterostructure growth on a substrate, without compromising the structural, spectroscopic, and device performances. The rare-earth-ion doped glass- and crystal-based devices are pumped with semiconductor lasers, suggesting that the glass-semiconductor devices might perform better when structurally integrated which may also help in reducing the pump-power for achieving efficient population inversion.

We explain the applications of PLD for controlling the structure of thin-films grown on inorganic and metallic substrates for photonic device and photo-active coatings for biological applications, respectively. Examples of materials deposited on dissimilar substrates are discussed with applications such as photonic devices and photo-bioactive surfaces for sensing.

We review recent works in signal shaping and advanced characterization techniques within the framework of nonlinear fiber optics. Here, we focus on characterization methods based on the dispersive Fourier transform to monitor incoherent spectral broadening processes with enhanced resolution and sensitivity. In this framework, we further discuss recent studies of modulation instability in a noise-driven regime. Paired with suitable optical monitoring techniques, we show that controlled coherent optical seeding can be leveraged using suitable machine learning approaches to tailor and optimize incoherent spectral broadening dynamics.

Photonics has proven to be a promising platform for the implementation of neuromorphic architectures. In this context, we implement an optoacoustic recurrent operator (OREO) based on stimulated Brillouin scattering in a highly nonlinear fiber. We demonstrate how OREO can establish a connection between optical pulses through acoustic waves. We show how the depth of our network benefits from cooling the fiber, as this extends the acoustic lifetime. We use OREO under this concept to perform a pattern classification task with 67% accuracy.

High harmonic generation (HHG) stands as one of the most complex processes in strong-field physics, as it enables the conversion of laser light from the infrared to the extreme-ultraviolet or even the soft x-rays, enabling the synthesis and control of pulses lasting as short as tens of attoseconds. Accurately simulating this nonlinear and non-perturbative phenomena requires the coupling the dynamics of laser-driven electronic wavepackets, described by the three-dimensional time-dependent Schrödinger equation (3D-TDSE), with macroscopic Maxwell’s equations. Such calculations are extremely demanding due to the duality of microscopic and macroscopic nature of the process, thereby requiring the use of approximations. We develop a HHG method assisted by artificial intelligence that facilitates the simulation of macroscopic HHG within the framework of 3D-TDSE. This approach is particularly suited to simulate HHG driven by structured laser pulses. In particular, we demonstrate a self-interference effect in HHG driven by Hermite-Gauss beams. The theoretical and experimental agreement allows us to validate the AI-based model, and to identify a unique signature of the quantum nature of the HHG process.

Disordered, self-assembled media, contain a large amount of information, which can be seen as a huge set of random and uncontrolled memory patterns. In the framework of optics, in which an opaque medium may modelled with the transmission matrix approach, each transmitted mode “contains” a memory element which is embodied by the correspondent transmission vector. Even if the stored amount of information in this system is huge, these random memories cannot be tailored easily. Here we present a new approach to write, read, and classify memory patterns: the photonic emergent learning. The writing paradigm is borrowed form a-physical- mathematical model for the biological memory, the emergent archetype, which we translated to photonics. In our approach the random patterns enclosed in the transmitted electromagnetic modes, are used as prototypes which are summed in constructive fashion in order write our target archetype-memory into our disordered optical memory (DOM). The DOM can work as a content addressable memory, retrieving at the lightning speed which memory in the library is the closest to an optically proposed query pattern. Moreover, the optical memories can be organized into super structures containing memories of the same thus efficiently delivering a classification task.

We describe our use of deep learning to optimize the multi-dimensional parameter space of systems-on-chip as an important step towards the scalable production of photonic solutions and their widespread integration into high-volume applications. The challenges of transitioning between prototype and volume production are highlighted, and the suitability of deep neural networks for navigating the multi-dimensional design space of today’s photonic circuits is discussed. We adopt multi-path neural network architectures to reduce the computational requirements of model training and to mitigate the risk of overfitting. We demonstrate the use of a multi-path neural network to optimize the construction parameters of photonic designs in a high-volume production environment. Lastly, we discuss the advantages of using machine learning not only as a highly capable tool for navigating the multi-dimensional design space of complex systems-on-chip but also as an effective strategy for compensating for fabrication process non-uniformities that are undetectable by standard process metrology instruments.

We present two distinct types of 'smart' surfaces designed for facilitating the quantitative exploration of dynamic processes occurring at sub-wavelength distances from interfaces, using far-field optical techniques. Based on evanescent waves in excitation and/or emission, we achieve an axial localization precision of about 10 nm. The first type of substrate incorporates nanocavities in a thin metallic film, enhancing and confining the electromagnetic field to a tiny volume. The second sample consists of a thin fluorescent film sandwiched between transparent spacer and capping layers deposited on a glass coverslip. The emission pattern from this film codes detailed information about the local fluorophore environment, namely, the refractive index, defects, reciprocal lattice, and the axial distance of the molecular emitter from the surface. An application to axial metrology in total internal reflection fluorescence and axial super-localisation microscopes is presented.

Emission patterns from molecules at interfaces encode many details about their local environment and their axial position, along the microscope’s optical axis. We introduce an advanced approach that synergizes back focal plane (BFP) imaging with innovative 'smart' surfaces make surface imaging more qualitative, more reliable, and more robust. Our method is particularly focused on accurately measuring the refractive index (RI) of transparent thin films and their imperfections close to the interfaces. Our technique utilizes a 'smart' surface, which features a uniform fluorescent thin film of about 4 nm thickness together with back-focal plane (BFP) imaging. We manage to detect bubbles or other imperfection in 100 nm thin film of polymer with RI of 1.34.

Coherent fiber bundles (CFB) are used in endoscopes for instance in biomedical diagnosis or optical inspection for industrial processes. Their working principle is based on the pixelated intensity transfer via several thousands of fiber cores, within a single monolithic structure. Due to scattering of the effective refractive index in the fiber cores, all phase information is lost. Thus, CFB endoscopes conventionally offer pixelated 2D imaging only, whereas the distal optics used for (de-) magnification enhances the endoscope diameter typically beyond 2 mm and suffers aberrations.

Measuring the optical transfer function of the CFB or more specifically the phase distortion enables correcting said distortion. Advances in CFB endoscopy are presented and discussed. This encompasses single-sided self-calibration and video rate 3D imaging without distal optics based on digital optical phase conjugation using a spatial light modulator. Deep learning is used for real-time complex light field generation as well as image deconvolution. Furthermore, a CFB with bending invariant OTF is introduced. In combination with laser-based manufacturing, this enables an ultrathin and mechanically flexible optical lens. The novel component can be integrated into standard widefield or raster scanning microscopes to enable endoscopic applications with diameters below 400 µm and 1 µm resolution.

The new polarization-holographic element of an optimal configuration is developed for the real-time complete analysis of the polarization state of light (for determining all Stokes parameters). The simultaneous measurement of the intensities in all points of images in diffracted orders using CCD camera and appropriate software allows to determine the spatial distribution of a polarization state in the images of objects, and also the dispersion of this distribution.