Conference Agenda

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.