I will review our recent work in advanced applications of optical microcombs to optical neural networks, optical communications and other areas.

Thin film aluminum nitride on insulator (AlNOI) has gained attention as a promising material platform for integrated photonic circuits (PICs) due to its ability to operate over a wide spectral range covering the ultra-violet to mid-infrared regions, while enabling a broad range of passive photonic functionalities. This study aims to optimize sputtered AlNOI films for PICs, with an emphasis on the spectroscopic ellipsometry study over a range from 0.19 µm to 25 µm. Furthermore, we discuss our approach for fabricating AlNOI PICs components, with a particular focus on optimizing the etching process to attain smooth sidewall waveguides.

In last years, the introduction of 2-dimensional materials such as graphene has revolutionized the world of silicon photonics. In this work, we demonstrate a new approach for integrating graphene into silicon-based photodetectors. We leverage a thin film of hydrogenated amorphous silicon to embed the graphene within two different photonic structures, an optical Fabry-Perot microcavity, and a waveguide, achieving a stronger light-matter interaction. The investigated devices have shown promising performance resulting in responsivities as high as 27 mA/W and 0.15 A/W around 1550 nm, respectively.

Novel applications in optical coherence tomography (OCT) and LiDAR systems have become possible due to performance characteristics of a state-of-the-art silica-on-silicon planar lightwave circuit (PLC) platform. We have achieved ultra-low propagation losses of <0.009 dB/cm with unmatched phase control in a polarization-insensitive way, enabling a range of real-time advanced vision and imaging applications utilizing k-clocks and analog frequency sampling architectures.

We describe a selection of work carried out within the ECSEL-VIZTA European research project concerning the development of an integrated solid-state 905nm time-of-flight (TOF) LIDAR device. Pseudo two-dimensional, single wavelength beam steering from a 7x32 channel silicon nitride-based optical phased array was achieved, with optimized single-pass thermo-optic phase shifters with Pπ = 30mW. Direct optical coupling of a photonic chip to a 7 W tapered GaInAsP laser diode is also shown to suggest a pathway to achieving medium-to long-range integrated LIDAR using a low-cost light source.

Recently, pulsed laser deposition has been utilised to fabricate multi-component thin films and embed

dissimilar materials (polymer and glasses) and nanoparticles from rare earth ions doped glasses target. This review

presents the results of ns/fs-PLD fabrication of the rare-earth-doped multicomponent glass thin films onto semiconductor

and silica substrates for engineering optically active optical waveguides for amplifiers, lasers and integrated sensor

applications. We present the results of waveguide analysis by investigating the surface morphology, cross-section, and

the fraction of crystalline phase using electron microscopy and X-ray diffraction. In addition, other complementary

characteristics such as refractive index, photoluminescence and lifetime, and optical gain properties will be presented.

Ultrashort pulse (USP) laser ablation is gaining popularity as a novel manufacturing technique for brittle materials, enabling the creation of complex freeform shapes that are challenging to produce with conventional optics manufacturing techniques. Freeforms have revolutionized optics manufacturing by providing designers with increased degrees of freedom using non-rotational symmetric components. However, this evolution presents new challenges for manufacturing processes, calling for innovative solutions such as USP ablation. To ensure the industrial viability of areal USP laser machining, it is crucial to not only consider material removal rates but also surface quality and subsurface damage (SSD). Especially for optical applications, harsh quality requirements must be met. This study investigates the SSD patterns of fused silica (FS) and borosilicate glass N-BK7 (BK) processed under different laser wavelengths, beam geometries and processing parameters using high-resolution optical coherence tomography (OCT). It is shown that OCT as non-destructive and 3D evaluation method is well-suited for analysing USP processes. The discovered differences in defect morphology between FS and BK emphasize the importance of selecting appropriate processes and process parameters when working with different materials. Compared to previous studies which used destructive techniques for SSD analysis, OCT revealed higher defects depths of up to 441 µm.

Analysis of defects in optical materials is essential for their applicability in cutting-edge optical components. Since fused silica (FS) counts among the most used materials, deep knowledge about the defects in FS is of high importance. These defects have been routinely identified by studying photoluminescence (PL) emission and its analysis via multiple Gaussian bands. Here we present an extended approach based on the Franck-Condon model to study the defects in FS and the connected pathways of charge carrier relaxation. First, we performed the optical characterization of the FS, including optical absorption, photoluminescence (PL) emission and excitation (PLE), and Fourier-transform infrared (FTIR) and Raman spectroscopy (RS). Based on the analysis of the PLE spectra and vibrational frequencies via RS and FTIR, we created a multi-transition Franck-Condon model, which is able to fully reproduce the PL and PLE spectra. Based on the experimental data and the Franck-Condon fit, we discuss two types of oxygen-deficient centres (ODC) present in this fused silica material and their emission pathways.

Stochastic Si nanostructures for antireflection (AR) fabricated by reactive ion etching (RIE) are presented for use in different spectral ranges. The lithography-free fabrication enables its application on highly curved surfaces. ALD-coatings of Al2O3 of varying thickness can improve the mechanical stability of such structures while keeping their optical functionality. While typical black silicon structures are suitable for application from VIS to NIR, an RIE-based fabrication process for stochastic AR structures in the longer IR and THz range is presented as well.

Over the last 15 years, there have been tremendous progress in the technology of optical interference filters. Nowadays, it is more and more common to fabricate optical interference filters that can combine several tens to several hundreds of layers in order to produce more and more complex optical functions. These progresses are the result of improved multilayer structures modeling and design procedures, the introduction of Virtual Deposition Process, and the development of performant physical vapor deposition machines associated with in-situ optical monitoring. In this paper, we will present actual state-of-the-art of these technologies and some typical examples of filters. We will then present some of the actual challenges and outlook in order to produce more and more performant optical components.

Achieving efficient mixing of fluids is a great challenge in microfluidics that has been addressed using microstructures. In this work, Stereolithography (SLA) and Pulsed Laser Ablation (PLA) were combined to manufacture a straight micromixer for uniform mixing of fluids. Computational Fluid Dynamics (CFD) simulation was performed to test the device. The results suggest that the combination of these optical technologies can be an effective method for fabricating microfluidic devices with great mixing capabilities.

A new concept for synchro-speed polishing of flat and spherical surfaces is introduced: 3D printed gradient index (GRIN) polishing tools. By using additive manufacturing technologies in combination with photopolymer plastics, GRIN tools can be fabricated that are individually adapted to the workpiece geometry. By using two different plastics, the hardness and therefore the removal rate of certain tool areas can be defined. Surface structures, benefiting material removal rate and tool wear rate, are possible as well as lightweight structures with high mechanically stability. Tools can be fabricated as thin foils as well as solid pads, ranging from small (few mm) to large diameters. Additionally, the pads can be fabricated with an individual radius. This can enable the replacement of radius-dependent tool holders, because the pads can be mounted on flat tool interfaces, since the radius is not dependent from the tool body anymore. First results from the experimental setup are showing, that by using GRIN foils similar surface quality results can be achieved in comparison to conventional polyurethane foils, while the GRIN foils are offering a lot more possibilities regarding process optimization.

We measure the modal dispersion occurring in a single multimode fibre and account for this using a digital micromirror device to form a raster scanning spot in the far field of the distal facet of the fibre. We perform this with a q-switched 700~ps pulsed laser at a 532~nm wavelength. The raster scanning allows us to spatially interrogate the reflectivity of a scene while the time of flight of the pulse gives distance information allowing for the generation of a three-dimensional image.

This study presents an initiative aimed at developing a real-time optical measurement system for non-contact measurement of fungal spores in protected crops such as strawberries, tomatoes, and cucumbers. The measurement system is based on a modified microscope combined with automatic spore trapping and air sampling. The system has been used in field trials. Work is ongoing to develop image-processing and YOLO-based object classification network algorithms to identify and classify fungal spores in high-resolution microscope images in the presence of pollen, dust, and other aerosols.

Albedo plays a vital role in urban microclimates. Civil engineering structures usually absorb a high amount of energy in form of heat, for example asphalt pavements, which have a low albedo, thus contributing to the Urban Heat Island (UHI) effects. Modifying the physical characteristics of asphalt pavements, including reflectance and thermal properties, can help mitigate UHI. The literature points out that one alternative to thermoregulating asphalt materials is the incorporation of phase change materials. Thus, the main goal of this research is to present a systematic review regarding the effectiveness of the incorporation of polyethylene glycol (PEG) 1000, 2000 and 4000 as Phase Change Material (PCM) in asphalt materials. The results showed that incorporating PEG into asphalt materials can regulate heat storage, promoting stability and reducing UHI effects. PEG2000 was more frequently used. PEGs can reduce between of 3.5 and 4.2ºC of the asphalt materials when compared to the conventional ones.

The aim of kW-flexiburst is to develop a high-power Ultra-short Pulse (USP) laser generating bursts that can be arbitrarily adjusted in terms of burst repetition rate, intra-burst repetition rate, number of pulses per burst, relative intensities in the burst while maintaining 1 kW average power. This will be enabled by a radically new concept of seed oscillator, which offers the opportunity to work at GHz repetition rates.

This high power USP laser will be adaptable to efficiently process any material (metals, dielectrics, semiconductors) using a variety of laser parameters that can be continuously tuned from a few high energy pulses to a large number of pulses in a high repetition rate burst.

The flexible laser performance will be demonstrated in relevant industrial applications, which require high throughput/ high quality laser processing methods and therefore will benefit significantly from the high mean power and the tunable pulses provided by the kW-flexiburst system.

The selected applications span a wide range of industrial fields from micro-structuring of metals, ceramics and other dielectrics, drilling of hard substrates and cutting of transparent materials. Each of them carries the potential for significant or even disruptive improvements of the related industrial production process by employing the kW-flexiburst laser technology in combination with the beam delivery concepts and process methods proposed by the project.

Photoelectrochemical cells (PECs) that mimic photosynthesis belong to the group of direct systems for converting sunlight to stored chemical energy. Common to those is the potential to become more efficient and cost effective because, unlike indirect ones, they do not involve unnecessary steps such as the sunlight to electricity conversion. Despite their greater potential, there is yet no direct conversion device that works on any technological scale. Indeed, there seems to be a large barrier linked to a poor PEC efficiency in absorbing sunlight and driving the catalysis for water oxidation (WO) and selective CO2 reduction (CO2R) to carbon-based compounds to store chemical energy. In addition, most PEC designs incorporate non-abundant or highly toxic elements precluding their future use at a larger scale.

In LICROX we will implement a new PEC type incorporating three complementary light absorbing elements driving WO and CO2R. The latter consists of a tandem assembly that combines Cu nanocatalysts with molecular catalysts made of only abundant elements. BiVO4 photoanodes have been fabricated and incorporated in tandem structures with organic photovoltaics (OPV) providing sufficient photovoltage and photocurrent to drive the bias free CO2R reaction to C2 products, targeting ethylene. Several light trapping mechanisms have been incorporated, which have been proven to be very effective in boosting the light harvesting efficiency in thin film solar cells.

To accelerate the endeavor of converting the triple junction PEC proposed into a working technology for transforming light and CO2 into compounds capable of storing chemical energy, LICROX brings together an interdisciplinary team of scientists with a comprehensive expertise in materials chemistry, semiconductor physics, electrochemistry, and photonics from EPFL, TUM, ICIQ and ICFO. Designing a strategy by DBT to overcome societal resistance, LICROX will set the route for a new scalable renewable energy technology to be initially pushed towards an industrial implementation and commercialization by AVA, HST and a newly developed spin-off from ICFO.

In this talk, the overall LICROX project will be exposed, and the light management will be specifically targeted by ICFO's presenter.

With the total amount of worldwide data skyrocketing, the global data storage demand is predicted to grow to 1.75 × 10^14 GB by 2025. Traditional storage methods have difficulties keeping pace given that current storage media have a maximum density of 10^3 GB/mm3. As such, data production will far exceed the capacity of currently available storage methods. The costs of maintaining and transferring data, as well as the limited lifespans and significant data losses associated with current technologies also demand advanced solutions for information storage. Nature offers a powerful alternative through the storage of information that defines living organisms in unique orders of four bases (A, T, C, G) located in molecules called deoxyribonucleic acid (DNA). DNA molecules as information carriers have many advantages over traditional storage media. Their high storage density, potentially low maintenance cost, ease of synthesis, and chemical modification make them an ideal alternative for information storage. To this end, rapid progress has been made over the past decade by exploiting user-defined DNA materials to encode information. In our project we explored data storage relying on DNA nanostructures (as opposed to DNA sequence) as well as on other combinations of nanomaterials.

It is estimated that 10 % of global greenhouse gas emissions are related to cooling buildings and environments. With demand for cooling expected to grow tenfold by 2050, and the increasing frequency of extreme heat waves, improving the efficiency of cooling systems plays a critical role in addressing the global climate challenge. Passive Radiative Cooling (PRC) materials – an emerging technology that can cool to sub-ambient temperatures, even in direct sunlight, without using electricity – could be an efficient alternative to conventional systems to save energy and reduce heat gains. However, the lack of standardisation and guidance for testing PRC materials and their properties, along with no standardised methods for testing their real-world performance, are limiting their uptake.

The PaRaMetriC project aims at developing a metrological framework to classify and compare PRC materials, assessing and validating appropriate benchmark materials and laboratory testing methods. It will also focus on characterising the properties of PRC materials and develop modelling methods, setting standards for quality control and allowing long-term effectiveness to be evaluated. The project will also create protocols and best-practice guides for in-field testing and set up long-term tests across several sites to assess material performance under a variety of real-world conditions. This project will help drive innovation in PRC technology, producing more energy-efficient cooling to meet rising needs.

ENSEMBLE

Optical clocks based on trapped laser-cooled atoms and single ions have demonstrated frequency stability and estimated systematic frequency uncertainty far surpassing the current generation of caesium microwave frequency standards, with the result that a future optical redefinition of the SI second is anticipated. However before this can happen several key challenges remain to be addressed.

Firstly, the uncertainty budgets of the optical clocks need to be validated through a programme of international comparisons between systems developed independently by different research groups around the world. Continuity with the current caesium-based definition must also be ensured, by performing absolute frequency measurements with as low an uncertainty as possible. And finally, we need to improve the robustness of optical clocks and automate their operation. This will enable them to be operated routinely as secondary representations of the second, regularly contributing to International Atomic Time (TAI) via reporting to the International Bureau of Weights and Measures, and being used to steer the local UTC(k) time scales maintained by national timing laboratories.

I will discuss recent progress towards addressing these challenges, in particular drawing on examples of work performed in the European collaborative project Robust Optical Clocks for International Timescales (ROCIT).

Using near-infrared light, we tightly-lock a mid-infrared quantum cascade laser frequency comb to another laser, achieving a residual integrated phase noise of 200 mrad. This high coherence is pertinent for highly-sensitive dual-comb spectroscopy and metrology.

We will report our recent progress toward H2+ spectroscopy by use of a SI-referenced Mid-IR source laser. H2+ molecular ions are very interesting candidates to improve the determination of fundamental constants, such as the proton to electron mass ratio mp/me and search for new physics beyond the standard model. At LKB, an erbium fibered frequency comb is phase locked to the LNE-SYRTE frequency standards thanks to the T-REFIMEVE network. By sum frequency generation in a AgGaSe2 crystal between a CO2 laser and an output of the comb at 1895 nm, a shifted frequency comb centered at 1560 nm is generated. The latter is then mixed with the original one to generate a beatnote used to stabilise the Mid-IR laser. As a first application, a narrow saturated absorption line in formic acid has been extensively studied. Pressure, power and modulation depth shifts and broadenings have been evaluated, leading to a determination of its central frequency at a sub ppt (10^-12) resolution, high enough for H2+ spectroscopy and fundamental constant determination.

Dual-comb systems have demonstrated their potential for metrology, e.g. spectroscopy vibrometry or ranging. However, the implementation of dual-combs is often complex and generally requires substantial optical and optoelectronic hardware. Here, we propose a simple and compact architecture based on a bidirectional frequency shifting loop, that provides more than 100 mutually coherent comb lines. The system makes use of a CW laser and a slow electronic detection chain (10 MSa/s). We have implemented two configurations enabling dynamic multi-heterodyne interferometry at 20kHz: the first one makes use of acousto-optic frequency shifters, and allows highly sensitive distributed acoustic sensing along a fiber. The second one involves electro-optic frequency shifters, and enables ranging with a sub-mm resolution.

We show that our developed free-running, bidirectional ring Ti:Sa laser cavity meets the requirements for Dual Comb Spectroscopy in the UV range (UV-DCS). Two counter-propagative frequency combs with slightly different repetition rate are generated in such a cavity and we show quantitatively that this repetition rate difference can be explained by the self-steepening effect. Molecular absorption lines of the O2 A-band centered around 760~nm are measured with a 1,5 GHz spectral resolution, demonstrating that the mutual coherence of the two combs allows GHz-resolution DCS measurements. Moreover, we demonstrate that the generated output peak power allows for efficient second harmonic generation (SHG), in the scope of developing laboratory and open-path UV-DCS experiments.

Neuromorphic models are proving capable of performing complex machine learning tasks, overcoming the structural limitations imposed by software systems and electronic neuromorphic models. Unlike computers, the brain uses a unified geometry whereby memory and computation occur in the same physical location. The neuromorphic approach tries to reproduce the functional blocks of biological neural networks. In the photonics field, one possible and efficient way is to use integrated circuits based on soliton waveguides, ie channels self-written by light. Thanks to the nonlinearity of some crystals, propagating light can write waveguides and then can modulate them according to the information it carries. Thus, the created structures are not static but they can self-modify by varying the input information pattern. These hardware systems show a neuroplasticity which is very close to the one which characterize the brain functioning. The solitonic neuromorphic paradigm this work introduces is based on X-junction solitonic neurons as the fundamental elements for complex neural networks. These solitonic units are able to learn information both in supervised and unsupervised ways by unbalancing the X-junction. The storage of information coincides with the evolution of structure that changes plastically. Thus, complex solitonic networks can store information as propagation trajectories and use them for reasoning.

Machine learning has opened a new realm of possibilities in photonic circuit design and manufacturing. First, we describe our approach of using deep learning to optimize the multi-dimensional parameter space for hundreds of optical chips on a mask, resulting in homogeneity of performance in high volume applications. Second, we present our approach of using a support vector machine to predict the performance of optical devices by wafer probing. This approach eliminates the expensive and labour-intensive process of optical chip testing, and allows unprecedented control over the fabrication process, including in-situ monitoring of wafer fabrication and real-time process adjustments. The combination of these two approaches paves the way for accelerated adoption of photonics in high volume applications.

We demonstrate spontaneous emission of discretized conical wave when an ultrashort pulse propagates nonlinearly in a multimode fiber. Our theoretical predictions are experimentally and numerically confirmed, providing a general understanding of phase-matched radiations emitted by nonlinear waves in multidimensional dispersive optical system.

We present a complete Mueller matrix (MM) imaging polarimeter based on liquid-crystal retarders and a pixelated polarization camera. The polarimeter is calibrated and optimized at the pixel level. Therefore, the instrument is applied for the precise characterization of optical components used for the generation of structured light, like patterned retarders and patterned polarizers.

ITO is a transparent conductive material commonly used in everyday life and for its potential in material research. In nonlinear optics for instance, ITO has shown great capabilities for harmonic generation in its epsilon-near-zero configuration. In this article, we demonstrate a completely new nonlinear behaviour from ITO thin layers. After a Ga-Focused Ion Beam (FIB) milling of the thin film, we observe nonlinear photoluminescence produced for tightly focused femtosecond pulses. The signal shares strong similarities with that commonly detected from noble metals. We show that the arising of this nonlinear photoluminescence originates from the radiative decay of metal-like hot electron distribution in the material and is associated to a modification of the optical properties by the Ga ions.

Genetic targeting of neuronal cells with activity reporters (calcium or voltage indicators) has initiated the paradigmatic transition whereby photons have replaced electrons for reading large-scale brain activities at cellular resolution. In parallel, optogenetics has demonstrated that targeting neuronal cells with photosensitive microbial opsins, enables the transduction of photons into electrical currents of opposite polarities thus writing, through activation or inhibition, neuronal signals in a non-invasive way1. These progresses have in turn stimulated the development of sophisticated wave front shaping approaches, based on computer generated holography and temporal focusing, to enable in depth “all optical” brain circuits interrogation with high spatial and temporal resolution2: an essential methodology to link neuronal circuits activity to the control of memory, learning and perception in pathological and healthy brain. Here, we will review the working principles of all-optical methods and will show few breakthrough applications where they have been used for the investigation of visual circuits in mice models.

The past decade has witnessed a step-change in the scale, complexity, and scope of quantum information processing with photonics. Breakthroughs include photonic chips with dense co-integration of a large number of components, deterministic single photon sources with large purity, and high efficiency single photon detectors. Within this framework Boson Sampling is a computational problem that has been proposed as a candidate to obtain an unequivocal quantum computational advantage. There is strong evidence that such an experiment is hard to classically simulate, but it is naturally solved by dedicated photonic quantum hardware, comprising single photons, linear evolution, and photodetection. This prospect has stimulated much effort resulting in the experimental implementation of progressively larger devices. We will review recent advances in photonic boson sampling, describing both the technological improvements achieved and the future challenges. We will discuss recent proposals and implementations of variants of the original problem, theoretical issues occurring when imperfections are considered.

Industrial processes such as smelting and sintering require stable and precise temperature control of furnaces. To achieve this, accurate temperature measurements are required. Pyrometry allows for contactless measurement of bulk materials and is particularly suitable for high temperature applications. One of the main influences on the accuracy of pyrometric measurements is the knowledge of the emissivity in the spectral measurement range. To reduce this dependence, two-color pyrometers or multi-color pyrometers can be used. With this in mind, the IRS is further developing their existing pyrometer technology by designing an advanced multi-channel pyrometer for bulk oven processes in a joint venture with Stange Elektronik GmbH and New Generation Kilns Grün GmbH. The design process is explained here and the different methods of achieving emissivity independence are examined.

The presented investigations build on the results already presented at EOSAM 2022 on the in-situ monitoring of grinding processes, in which high correlations between vibrometry, force and topography data of machined fused silica samples could already be proven. With the help of new measurement setups, it was possible to also detect high-frequency vibration components in CNC grinding processes and to check their effects on the resulting surface qualities. The investigations were carried out on a 5-axis CNC machine and monitored with the help of vibrometric and white-light interferometric measurement technology. The aim was to look at the influences of process-side parameters on the process vibrations and the resulting surface qualities.

Choice of lenses materials in optical design is crucial to reduce aberrations down to an acceptable level. Commercial glasses do not cover a continuous range of refractive indices and must be selected in a discrete library making them discrete variables in any optimization design process to achieve the final optical design to be manufactured. This paper proposes an alternative method to avoid the complicated discrete variables optimization process thanks to a two-steps continuous optimization methodology starting with fictitious glasses models before jumping to the real glasses optimization design. The illustration of this process and achieved results are presented on an example of optical system which validates our proposed method.

Smart lighting systems are capable of producing light when and where it is needed. Such functionality can be achieved with adaptive optical systems, which consist of one or multiple adjustable components, enabling illumination with a variable radiation pattern. This paper introduces the design of a compact, tunable optical system, allowing illumination with variable beam size and beam direction. We demonstrate how this system can be combined with computer vision and a feedback loop, to achieve a fully autonomous, smart illumination system.

High Optoelectronic Chromatic Dispersion in Ge PN-photodetectors is incorporated in an Optoelectronic Oscillator to achieve high sensitivity wavelength monitoring and strain sensing. The sensitivity is enhanced for higher oscillating mode numbers and lower cavity lengths.

The response of three of the most used commercial polymers (poly(vinyl chloride) (PVC), poly(ethylene terephthalate) (PET) and polypropylene (PP)) with different thermal properties under irradiation with high frequency (1 kHz-1 MHz) femtosecond (450 fs) multi-pulse (N=10-1500) laser at λ=515 (1.34 J/cm2) and 1030 (1.70 J/cm2) is reported. Thermal and ablative effects are observed after laser irradiations. The results are compared to a photothermal model that pretends to explain the heat accumulation effect of successive pulses irradiation. Thermal analyses (Modulated Differential Scanning Calorimetry (MDSC) and Thermogravimetry (TG)) are performed and utilized to explain the different behaviour of each polymer. Three different regimes (non thermal, thermal and saturation) are identified and explained from the model and experimental results. A connection between ablation depth and simulated reached temperature is established. Further studies as micro-Raman analyses on the irradiated area and the dependence of damaged area on the repetition rate are being performed.

Robust GHz Frequency Combs: a new tool for many applications

We demonstrate a multimode diode-pumped Yb:CALGO laser oscillator based on bandwidth-optimized cross-polarization pumping targeting sub-30-fs operation. In our first proof of principle experiment we achieved mode-locked operation at 83 MHz repetition rate with 0.4 W of average power and a 33-nm-bandwidth optical spectrum supporting sub-40-fs pulses. This concept offers a simple and cost-efficient alternative to green-pumped Ti:sapphire lasers.

We demonstrate generation of bursts that consist of up to 40 ultrashort pulses with 10 μJ pulse energy, 250 fs pulse duration and an ultrashort tunable spacing, from picoseconds to nanoseconds, corresponding to a terahertz intraburst repetition rate. This was achieved by the build-up of a novel thermally-stable sub-mJ Vernier Regenerative Amplifier (RA), whose round-trip detuning is similar to its master oscillator round-trip time. The RA includes two cavities pumped from a common diode, and is able to provide for either 2 bursts (one burst out of each cavity), or for one burst and a synchronous reference pulse for characterization.

Micromachining of various materials with femtosecond lasers operating in the GHz-burst regime has recently attracted great attention. In this contribution, we show our latest results on top-down percussion drilling in different dielectrics in this new operating regime. The dependence on the burst parameters such as burst repetition rate, number of pulses per burst, and burst energy are discussed. Moreover, we will focus on the influence of the burst shape on the drilling process. The quality of the drilled holes and their reachable dimensions are presented.

We employ real-time spectral measurements to investigate the transitions from the stable mode locking to period doubling and long-period pulsations. We highlight the role of self-phase modulation as a general mechanism triggering period-2 bifurcations. We analyze the new frequencies generated during the sequence of bifurcations and report an entrainment where the period of the long oscillation locks to multiples of the cavity roundtrip time.

We employ one- and two-photon polymerizatin, i.e. flash-TPP printing, which is compatible with metal-oxid-semiconductor (CMOS) technology, to fabricate polymer-cladded and single-mode 3D photonic waveguides and adiabatic splitters. Our 3D technology is a major step forward towards the highly-interconnection required in optical neural networks, which removes the high energy dissipation of electronics and where 3D integration enables scalability that is challenging to realize in 2D.

Photonic neural networks are a highly sought-after area of research due to their potential for high-performance complex computing. Unlike artificial neural networks, which use simple nonlinear maps, biological neurons transmit information and perform computations through spikes that depend on spike time and/or rate. Through comprehensive studies and experiments, a strong foundation has been laid for the development of photonic neural networks. We have recently developed a large-scale spiking neural network, consisting of more than 30.000 neurons, which serves as a proof-of-concept experiment for novel bio-inspired learning concepts. This breakthrough is significant because it demonstrates the potential of using photonic neural networks for advanced computing and highlights the importance of incorporating biological principles into artificial intelligence research.

Photonic computing has attracted much attention due to its great potential to accelerate artificial neural network operations. However, the processing of a large amount of data, such as image data, basically requires large-scale photonic circuits and is still challenging due to its low scalability of the photonic integration. Here, we propose a scalable image processing approach, which uses a temporal degree of freedom of photons. In the proposed approach, the spatial information of a target object is compressively transformed to a time-domain signal using a gigahertz-rate random pattern projection technique. The time-domain signal is optically acquired at a single-input channel and processed with a microcavity-based photonic reservoir computer. We experimentally demonstrate that this photonic approach is capable of image recognition at gigahertz rates.

We experimentally demonstrate an autonomous, fully tuneable and scalable neural network of 350+ parallel nodes based on a large area, multimode semiconductor laser. We implement online learning strategies based on reinforcement learning. Our system achieves high performance and a high classification bandwidth of 15KHz for the MNIST dataset. Our approach is highly scalable both in terms of classification bandwidth and neural network size.

A high-performance photonic reservoir, which utilizes the injection locking effect in a

highly multimodal semiconductor laser, has been developed. This innovative design allows for fully parallel and high-bandwidth operation. The output of this system is projected in space and imaged onto a digital micromirror device, which provides a readout and facilitates the hardware integration of programmable output weights. By using a highly multimodal semiconductor laser, the injection locking effect enables a large number of modes to be simultaneously locked to the injected signal, resulting in high dimensionality of the reservoir, reducing the computational time and complexity. The use of a digital micromirror device provides a flexible readout, allowing the output to be programmed to suit a range of applications. The hardware integration of programmable output weights enables the system to be optimized for specific tasks, improving performance and reducing power consumption.

In this paper, we experimentally demonstrated a novel all-optical reservoir computer with an all optical input mask. The combination of the binary random masks and the time-stretched ultrashort pulses has increased the system's classification performance. Compared with the traditional digital masks, this method shows superior classification performance in spoken-digit classification tasks and eliminates the need for high-speed modulation for digital masks.

UVA one-photon hyperspectral light sheet imaging was performed here to capture and reconstruct three dimensional metabolic maps of mouse embryos during development. We explored numerically and experimentally the advantages of phasor-based hyperspectral approach for detecting embryo metabolism with a single wavelength excitation compared to the conventional detection approach using bandpass filters.

In this work we present a microscope on a chip for automatic structured light sheet imaging of single cells. This integrated platform has been fabricated by femtosecond laser micromachining in glass substrates and it encompasses integrated optical elements such as waveguides, lenses and beam splitters as well as a microfluidic channel for sample delivery. Processing fluorescent cells, we have proven enhanced image resolution, automatic and continuous imaging as well as device ease of use

Root hairs are a delicate single-cell system whose growth is regulated by a fine mechanism characterised by the presence of a tip-high Ca2+ gradient that shows regular oscillations in growing root hairs. We show a method based on the use of Light sheet fluorescence microscopy (LSFM) which allows the quasi-physiological analysis of Arabidopsis thaliana plant roots hairs with excellent spatial and temporal resolution over a wide field of view. We show how the healthy growing root hairs are linked to precise oscillations and how a disruption of this mechanism can be associated to specific genes.

Minimally invasive endoscopy using coherent fiber bundles shows great potential for numerous applications in biomedical imaging. With a diffuser on the distal side of the fiber bundle and computational image recovery, single-shot 3D imaging is possible by encoding the image volume into 2D speckle patterns. In comparison to equivalent lens systems, a higher space-bandwidth product can be achieved. However, decoding the image with iterative algorithms is time-consuming. Thus, we propose utilizing a neural network for fast 2D and 3D image reconstruction at video rate. In this work, single-shot 3D fluorescence imaging with an ultra-thin endoscope is demonstrated, enabling applications like calcium imaging for in vivo brain diagnostics at cellular resolution.

Scanning fluorescence microscopes can image large tissues at the diffraction-limit. Scanning systems are also used for manipulation such as laser severing or optogenetic activation.

The conventional approach to image tissues with a scanning microscope involves scanning the entire bounding box enclosing the tissue, plane by plane, which is time-consuming and results in a high light dose.

We have developed a “smart” microscope that adapts its scanning scheme to the morphology of embryonic cell sheets, with no prior knowledge of the structure of interest. The surface of the tissue is first delineated from the acquisition of a very fractional scan of sample-space, using a robust estimation strategy. Subsequent high-resolution imaging can then be restricted to this targeted structure of interest, yielding a ~20-fold reduction in the scan path and, thus, an equivalent reduction in light dose and increase in speed. Additional scan path reduction can also be obtained using a propagative scanning approach. The resulting reduction in light dose (order of magnitude) is highly beneficial in terms of photobleaching.

We demonstrate the efficacy of our smart-scanning technique imaging Drosophila embryos and demonstrate how it can also be employed in a smart dissection scheme to make precise cuts on large non-planar tissues.

In this talk we introduce two new European projects DYNAMOS and ADOPTION, which will develop advanced integrated photonic technologies for WDM hyperscale data centre architectures including a novel stamped metallic micro-mirror array for advanced PIC-to-fibre coupling with the potential to dramatically reduce PIC design and assembly costs. We also discuss international standardization efforts for these corresponding optical interconnect technologies for future hyperscale data centre, HPC and 6G and Quantum environments.

We review our recent progress on advanced silicon photonic devices and photonic circuits, including advanced grating couplers, modulators, mode and polarization division multiplexing and integrated optical signal processors for use in high capacity data center interconnects. The use of shifted polysilicon overlay gratings on waveguide grating couplers to improve coupling efficiency and polarization independence will be described. We also present our recent results on silicon microring and silicon-germanium electroabsorption modulators for 100Gbaud data transmission and their use polarization and mode division multiplexed optical fiber interconnects. We present novel integrated optical signal processors which can unscramble the mixing of polarization and mode data lanes that will occur after fiber transmission and demonstrate 400Gb/s per wavelength intensity modulation direct-detection silicon photonic transceivers.

We discuss recent results related to the realization of integrated waveguide and fibre-based phase filtering devices for high-speed linear passive logic applications. A record frequency resolution of 1 GHz (a 10-fold improvement over standard optical waveshaper technology) is achieved using fibre Bragg grating-based phase filters. We have also succeeded in realizing Bragg grating devices with sub-mm2 device footprint based on spiral waveguides, paving the way for on-chip implementation. Using (all-pass) phase-only filtering devices, NOT and XNOR logic operations are demonstrated at ultrafast operation speeds with a few-fJ/bit energy consumption.

Femtosecond laser pulse irradiation enables precise control of conductivity in materials, revolutioniz- ing fields like nanoelectronics and materials science. It offers rapid modulation within femtosecond timescales, facilitating advancements in ultrafast electronics and high-speed data processing. In this talk, we will focus on the photoinduced reduction of conductivity in incommensurate crystals through excitation of electrons into localized states, revealing potential applications in optoelectronics, ultrafast switches, and photonic devices.

We present narrow-band polarization-sensitive reflectance of GaN/AlGaN heterostructures in the mid-infrared range. Experimental measurements performed at 15° angle of incidence show the excitation of a Berreman mode at the interface between GaN and sapphire substrate. A transfer matrix method for anisotropic layers has been used to analyze the obtained results. The contribution of the two-dimensional electron gas at the interfaces of the heterostructures has been included by proper modelization of an effective thin layer.

An overview of the applications of bound states in continuum (BICs) applications, from ultrasensitive sensing to giant enhancement of upconversion luminescence at Friedrich-Wintgen BIC, is reported. Perspective exploitation of this new class of devices is discussed.

Laser-induced periodic surface structures (LIPSS) have received considerable attention due to their potential for micro- and nanostructuring and surface functionalization of various materials. We present a novel application of LIPSS on a glass substrate as distributed feedback (DFB) laser resonators, capable of providing sufficient positive optical feedback to achieve lasing in thin-film waveguides with organic small molecules as a gain medium. The direct femtosecond micromachining allows for easy variation of the periodicity across a broad range of values, including those required to reach 1st Bragg order DFB operation. We investigate several small molecule organic thin-film systems and observe lasing in strong accordance with the underlying periodicities of all photonic structures involved. These results demonstrate the effectiveness of LIPSS as DFB laser resonators and suggest that they could facilitate the integration of organic thin-film media-based lasers and other photonic devices into various integrated photonic systems.

Thermal boundary resistance at the interface between carbon nanotubes and water is experimentally investigated measuring the nanotube cooling dynamics via ultrafast optical spectroscopy. This far-field non-contact technique allows quantitative measurement of the thermal boundary resistance and characterization of its dependence on the CNT size, the surrounding liquid and the specifics of the interface.

We demonstrate a nonlinear AlGaAs photonic chip generating biphotons with nonclassical spatial correlations. Photon pairs are generated by parametric down conversion in a waveguide array and simultaneously spread through quantum walks along the various waveguides. This concept implements a compact and versatile source of spatially entangled states, operating at room temperature and telecom wavelength, that could serve as a workbench for simulating condensed matter problems on-chip.

Integrated quantum photonics is a key tool towards large scale quantum technologies. In this work we present an AlGaAs-based photonic circuit for the on-chip generation of broadband orthogonally polarized photons and the deterministic separation of the photons into separate spatial modes, facilitating their further use in protocols. We demonstrate that 85% of the pairs are deterministically separated by the chip over a full 60 nm bandwidth and we assess the chip operation in the quantum regime via a Hong-Ou-Mandel experiment displaying a raw visibility of 75.5% over the same full bandwidth.

The Wigner phase-space formulation for systems possessing SU(1,1) symmetry has been defined by Seyfarth et al. [Quantum 4, 317 (2020)] tackling the difficulty in defining a suitable operational definition of the Wigner function. To further investigate this formulation, we propose a non-linear optical setup that incorporates photon-number-resolving detectors, which would enable a direct and comprehensive point-by-point sampling of the SU(1,1) Wigner function. We discuss the visualization of various two-mode quantum states and the effect of the losses in such a detection scheme.

Spontaneous Four Wave Mixing (SFWM) which generates photonic pairs is studied if it is addressed by optical vortices carrying an orbital angular momentum (OAM). We show that the output beams are OAM-correlated and that the entanglement depends on the 4-level scheme used to realize SFWM.

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DYNAMOS develops fast (1 ns) and widely tunable (>110 nm) lasers, energy-efficient (~ fJ/bit), broadband (100 GHz) electro-optic modulators, and high-speed (1 ns) broadcast-and-select packet switches as photonic integrated circuits (PICs). DYNAMOS meets the expected outcome objectives and call scope by proposing the development of low energy (few pJ/bit) PICs, which are integrated into modular and scalable subsystems, and subsequently utilized to demonstrate novel data centre networks with highly deterministic sub-microsecond latency to enable maximum congestion reduction, full bisection bandwidth (lower congestion) and guaranteed quality of service while reducing cost per Gbps.

The proposed network offers optical circuit switched reconfiguration and guaranteed (contentionless) full-bisection bandwidth, allowing any computational node to communicate to any other node at full-capacity. DYNAMOS builds on recent developments in III-V optoelectronics, thick silicon-on-insulator waveguide technology, and silicon organic hybrid (SOH) modulators. It co-develops the entire ecosystem of transceivers, switches and networks to boost overall performance and to reducing the total cost of data exchange, instead of focusing on the improvement of individual optical links or interfaces. The objectives of DYNAMOS perfectly match the major photonics research & innovations challenges defined in the Photonics21 Multiannual Strategic Roadmap 2021-2027.

There is an absence of lasers with the necessary wavelengths and characteristics to access the possibilities for deeper high-resolution biological tissue imaging in the third bio-window between 1650 nm and 1870 nm. Motivated by recent breakthrough results in multi-photon imaging at twice the depths currently achievable, we will meet the urgent need for new sources to address the outstanding research questions in this spectral region. Results will guide and enable instrument development in this appealing and relatively unexplored biophotonics imaging wavelength range.

The AMPLITUDE consortium proposes a new concept of label-free, multi-modal microscopy and endoscopic imaging operating in this new wavelength region with multiple imaging and spectroscopic technologies, including NIR confocal reflectance microscopy, multi-photon microscopy and spontaneous Raman spectroscopy.

By progressing ultrafast fibre laser developments at 1700 nm, we will deliver new imaging capabilities in an appropriate form factor and at cost suitable for widespread adoption. This will be further enhanced by providing additional output at 850 nm using second harmonic generation from one integrated laser device.

This will enable a pioneering new compact and efficient multi-modal capability combining confocal and non-linear imaging techniques, overcoming performance limitations in medical and biological imaging applications, including improved pathohistological staging of tumours and in-vivo endoscopic assessment of depth of lesion invasiveness. Deeper multi-photon microscopy with autofluorescence imaging of cellular metabolic conditions, whose aspects are tightly related to cellular functioning and to cancer, implemented in tandem with Raman spectroscopy will provide exhaustive characterisation of the examined tissue at morphological, metabolic and molecular levels, allowing in-vivo optical biopsy for bladder cancer diagnosis, grading and staging.

The continuous growth of the global population has been remarking the need of early detection systems to prevent the spread of epidemics as well as to improve the standards of living. The emerging demand of sensing technologies has prompted researchers and industrial companies to develop devices able to monitor medical, food, water, and environmental safety/quality indicators in an efficient, simple, and reliable way. While high sensitivity and selectivity must be guaranteed, compactness, user-friendliness and low-cost are key characteristics to enable the use of the sensing technology for point-of-care diagnostics without the need for trained personnel [1].

Among state-of-the-art methodologies for pollutants detection, optical sensing has emerged as one of the most simple, versatile, and powerful approaches for analytical purposes. However, a major obstacle towards the development of a portable system has been the use of bulky optical components (e.g. lasers and optical fibers), which are necessary to ensure a good sensing capability. In particular, huge interest has been attracted by functionalized metallic surfaces based on surface plasmon resonance (SPR), as extremely sensitive, label-free, quantitative systems for real-time detection of single or multiple analytes. However, the need of a fine and precise control of the angle of the incident light ended up in the use of not-portable optical components in the final sensor [2].

In this scenario, organic optoelectronic components might enable the definition of new miniaturized detection schemes to boost the advent of compact optical sensors for on-site analysis, given their inherent capability of smart monolithic integration in nm-thick multi-stack devices on almost any surface.

Here, we report an unprecedented ultra-compact system endowed with optical and plasmonic sensing capabilities through the smart integration of (i) organic light-sources such as organic light-emitting diodes (OLEDs) or transistors (OLETs), (ii) an organic light-detector such as organic photodiode (OPD) and (iii) a sensing nanostructured surface such a nanoplasmonic grating (NPG) [3]. The components and the layout of integration were suitably designed to make the elements work cooperatively in a reflection-mode configuration. In particular, the OPD was vertically stacked onto the source electrode of the OLET thus providing electrical switching, light-emission and light-sensing capability in a single organic multilayer architecture. When coupled to the NPG, a multifunctional system with SPR-sensing ability was obtained at a remarkably high level of miniaturizationat a sensor size as low as 0.1 cm3, arising from the direct fabrication of the NPG onto the encapsulating cap of the light-emitting/-sensing platform [4].

Once finalized into a working prototype and operated with standard solutions, the sensor is calibrated by providing quantitative and linear response that reaches a limit of detection of 10−4 refractive index units. Analyte-specific and rapid (15 min long) immunoassay-based detection is demonstrated for targets relevant for the milk chain. By using a custom algorithm based on principal-component analysis, a linear dose–response curve is constructed which correlates with a limit of detection as low as 3.7 µg mL−1 for lactoferrin, thus assessing that the miniaturized optical biosensor is well-aligned with the chosen reference benchtop SPR method.

[1] R. Dragone, …, S. Toffanin Frontiers in Public Health, 2017, 5, 1.

[2] M. Prosa, ..., S. Toffanin Nanomaterials 2020, 10, 480.

[3] M. Bolognesi, ..., S. Toffanin Adv. Mater. 2023 2208719

[4] M. Prosa, ..., S. Toffanin, Adv. Funct. Mater. 2021, 31, 2104927.

A high power 1.8 kW laser providing from picosecond down to femtoseconds pulses at repetition rates up to 1GHz with excellent beam quality will be developed and brought to the market at highly competitive costs enabling widespread industrial uptake. By harnessing the unique characteristics of patent protected tapered double-clad fiber amplifiers power-scaled multichannel laser, unparalleled high-power beam qualities, and pulse energies 2.5-250µJ will be achieved. Using the state-of-the-art highly stable laser diodes as seed lasers allowing parameter flexibility by ultrafast electrical control of pulse duration and repetition rate will a broad range of high-power laser processing application requirements to be met. An extremely stable advanced all-fiber based configuration allow development of a compact ultrashort pulse laser system. A newly-designed delivery fiber utilising cutting-edge technology of high purity glass material fabrication will be used to capable of handling the very high power ultra-short pulses, preserving beam quality over several meters distance. Pioneering technology based on 3D nano-imprint lithography will be exploited to produce coherent beam combining optics and fiber-facet-integrated micro-lenses for advanced beam shaping elements to elongate voxels. Together these will provide laser pulse delivery via patented polygon scanner technology capable of handling high-power pulses at speeds of up to 1.5 km/s. These will enable demonstration in automotive and renewable energy sectors of ultrafast 3D ablation, low-thermal welding of dissimilar metals and faster cost-effective cutting of ultra-hard materials. Exploitation in the form of high-power laser processing systems will immediately follow, benefitting from the unmatched performance data and detailed cost benefit and investment case analysis performed.

Hybrid organic-inorganic perovskites (HOIPs) with Cr3+ ions could be very useful in luminescence thermometry, especially in self-calibrating temperature sensing in a wide temperature range (10-400 K). The upcoming presentation will delve into the structural and optical characteristics of formate hybrid perovskites that incorporate Cr3+ ions. The primary focus will be on examining how the organic cation A+ affects the luminescent properties and temperature sensing capabilities of [A]B(HCOO)3:Cr3+ compounds. Additionally, the presentation will showcase the impact of substituting metal B on the structure, bond lengths, distortions of CrO6 octahedra, crystal field strength surrounding Cr3+ ions, and subsequently, the luminescence properties and temperature detection.

Conducting polymer nanoantennas enable active control of light-matter interactions at the nanoscale and are emerging as a new class of materials for dynamic plasmonics. While metal plasmonics is limited to static function due to fixed permittivity, we demonstrated for the first time that conducting polymer nanostructures can provide tunable plasmonic responses in the near infrared and infrared spectral ranges. Conducting polymer nanodisks of PEDOT:sulf could be modulated by chemical redox reactions[1] as well as by electrical tuning using a convenient ion gel device structure[2]. Furthermore, we showed that semiconducting polymer nanodisks made from PBTTT could provide reversible metal-to-dielectric transition by chemical doping/dedoping and thermal annealing[3]. I will present these studies and discuss our recent further developments within this new research direction of dynamic polymer nanooptics. The emergence of tunable polymer nanoantennas for dynamic plasmonics can be greatly expected for applications in advanced integrated optics, like dynamic holography and virtual reality.

Two-dimensional (2D) Transition Metal Dichalcogenide semiconductors (TMDs) are a promising platform in view of developing a novel generation of optoelectronics devices and renewable photon to energy conversion technologies. However new ultra-compact photon harvesting schemes are required to mitigate their poor photon absorption properties. In this work we propose a novel flat-optic solution where a few layers MoS2 film is conformally deposited on a large area (cm2) nanogrooved template. The subwavelength reshaping of the TMDs film induces the excitation of photonic Rayleigh Anomalies (RA). The latter promote a strong in-plane electromagnetic confinement and can be easily tuned over a broadband spectrum by tailoring the illumination conditions. As a demonstration of the potential of this large-area surface functionalization we employed the hybrid 2D nanopatterns as a photocatalyst in a prototype photobleaching reaction of Methylene Blue (MB) molecules. We demonstrate a strong enhancement of the photochemical MB degradation, well above a factor 2, by effectively tuning the RA mode in resonance to the molecular absorption band. Therefore, these findings pave the way to flat-optics photon harvesting schemes for boosting photoconversion efficiency in large-scale hybrid 2D-TMD/polymer layers, with a strong impact in applications ranging from waste-water remediation to new-generation photonics and renewable energy storage.

Fiber-based sensors have become a promising platform for the development of remote sensing solutions, allowing in-situ and faster responses. These devices are continuously evolving and new methods of improving their performance are constantly being developed, such as the use of chemosensor agent to generate or enhance the signal to be detected. In this sense, lanthanide metal-organic framework (Ln-MOFs) has shown great potential for sensing several analytes, such as gases and volatile organic compounds (VOCs). This work aims to develop sensors based on optical fibers coated with luminescent Ln-MOFs for remote sensing. Oxide glasses were used as a substrate for the in-situ growth of Ln-MOFs synthesized from EuCl3 and carboxylate ligands, specifically trimesic (1,3,5-benzene tricarboxylic) and pyromellitic (1,2,4,5-benzene tetracarboxylic) acids. The Ln-MOFs were deposited on glass bulks and optical fibers and had its structural and photoluminescent properties investigated. The composites were exposed to different organic analytes and photoluminescence measurements revealed a luminescence quenching in the presence of acetone. Thus, such composites seem promising for VOCs sensors, and remote sensing tests can be performed using optical fibers.

Mid-Infrared methane (CH4) spectroscopy results were obtained in band III beyond 7 µm. To achieve this, the generation of supercontinuum covering the spectral range between 5 and 12 µm was realized by using purified chalcogenide optical fibers free of highly toxic elements such as arsenic and antimony. Besides a pumping with an optical parametric amplifier, an all fibered pumping scheme has also been investigated. In both configuration, supercontinuum absorption spectroscopy experiments have allowed for CH4 sensing, concentration as low as 14 ppm has been detected.

Thin-disk laser oscillators can nowadays reach few tens of femtosecond pulses at gigawatt-level intracavity powers and megahertz-repetition rates becoming increasingly more powerful sources for intra-oscillator high harmonic generation (HHG). Currently, we can generate high harmonics in neon reaching photon energies of 70 eV, which we expect to increase toward 100 eV in the near future. In parallel, the achievable average and peak output powers of these oscillators in the range of 100 W and 100 MW, respectively, make these sources very promising to drive HHG in single-pass configuration after nonlinear pulse compression. Starting from transform-limited 30 to 50-fs soliton output soliton pulses of TDL oscillators, we will likely see these lasers approaching a single-cycle regime becoming highly attractive sources for attosecond science.

We present a table-top, efficient and power scalable scheme enabling the effective generation of extreme ultraviolet radiation up to 100 eV photon energy. Therefor ultrashort pulses (< 20fs) in the visible spectral range (515 nm) are used to drive high harmonic generation in helium. This allows for a significant efficiency boost compared to near-infrared (NIR) drivers, enabled by the favourable scaling of the single-atom response of λ-6 [1]. The experimental realization of a mulitpass cell delivering 15.7 fs pulses with a peak power close to 25 GW at 515 nm and an overall efficiency (IR to compressed green pulse) of >40 %. In conjunction, preliminary HHG results will be presented, paving the way for mW-class HHG sources at 13.5 nm.

The technological refinements on high-power laser systems of Petawatt class unveil scenarios for light-matter interaction beyond the laser-plasma perspective. In this contribution we explore the possibility of assisting high-harmonic generation (HHG) with the strong magnetic field associated with one of those intense sources. Recently, there has been an interest in developing schemes to employ intense laser beams to define spatial volumes in which strong magnetic fields are found isolated from the electric field. In this conditions, the magnetic field can be used to assist the harmonic generation from atoms from standard drivers. We demonstrate that, using the proper interaction geometry, the magnetic field confines the transversal dynamics of the continuum electrons allowing, on one side, to enhance the efficiency of the electron rescattering that produces the harmonic radiation and, on the other side, to excite the electron transverse dynamics and to convert this energy into phase-locked harmonic photons of few hundreds of eV.

We report on a high energy ultrafast fibre laser architecture designed for high harmonics generation in solids. The laser delivering 50 fs pulses with 2.12 µJ at 1550 nm has enabled the generation of harmonics up to harmonic H5 from a magnesium oxide (MgO) bulk sample. To the best of our knowledge this is the first solid-state HHG source driven by a µJ-class few-cycle fiber laser in the mid-IR region.

A phase-matching free pulse retrieval technique based on plasma-induced defocusing in a rare gas is presented. Based on a pump-probe setup, this technique uses a moderately intense pump laser pulse for ionizing the medium, creating in turn an ultrafast defocusing lens. While a coronagraph blocks out the probe pulse in absence of ionization, the plasma lens leads to increase the probe beam size in the far field. By measuring the spectrum of the probe propagating around the coronagraph as a function of the pump-probe delay t, a bi-dimensional trace (w-t) is obtained. This enables to fully characterize the temporal and spectral characteristics of the probe pulse through a method that is free of phase matching constraints. Demonstrated both in the near-infrared (800 nm) and in the ultraviolet (266 nm), the present technique is potentially suited for characterizing pulses in the whole transparency region of the used gas, i.e., from the deep-ultraviolet to the far-infrared.

We point out the breakdown of two approximations widely used to describe decoherence in open quantum systems, the secular and Markov approximations. We probe their limits by studying the influence of pressure on the alignment revivals (echoes) created in properly chosen gas mixtures (HCl and CO2, pure and diluted in He) by one (two) intense and short laser pulse(s). Experiments, as well as predictions using molecular dynamics simulations, consistently demonstrate in some of the aforementioned systems the break-down of these approximations at very short times (<15 ps) after the laser kick(s).

Deep neural networks are increasingly applied in many branches of applied science such as computer vision and image processing by increasing performances of instruments. Different deep architectures such as convolutional neural networks or Vision Transformers can be used in advanced coherent imaging techniques such as digital holography to extract various metrics such as autofocusing reconstruction distance or 3D position determination in order to target automated microscopy or real-time phase image restitution. Deep neural networks can be trained with both datasets simulated and experimental holograms, by transfer learning. Overall, the application of deep neural networks in digital holographic microscopy and 3D computer micro-vision has the potential to significantly improve the robustness and processing speed of holograms to infer and control a 3D position for applications in micro-robotics.

Modern optical microscopes, from super-resolved fluorescence to label-free mechanisms of contrast, are powerful instruments able to produce images that are rich sources of molecular information towards an unprecedented insight into the morphological and functional properties of biological cells at the nanoscale. Today we are in the realm of multimodal optical microscopy boosted by artificial intelligence that makes intelligent the microscope. Super-resolved fluorescence microscopy, incorporating photochemical parameters from brightness to lifetime, and non-linear approaches, like those associated with multi-photon excitation able to exploit intrinsic fluorescence and SHG/THG, is coupled to label-free polarisation methods like Mueller matrix microscopy, expanding the available data set. Such a data set is the core for developing an artificial microscope aiming to transform a label-free interrogation of the sample into a molecular-rich fluorescence-based image. The intelligent microscope is AI-guided through a computational core based on three modules based on a convolutional neural network (CNN) and a tensor independent component analysis (tICA) un-supervised machine learning within a supervised deep learning strategy having the ambitious target to create a robust virtual environment "to see "what we could not perceive before". An interesting case study is related to understanding the visualisation of chromatin organisation.

Optical approaches have made great strides enabling high-speed, scalable computing necessary for modern deep learning and AI applications. In this study, we introduce a multilayer optoelectronic computing framework that alternates between optical and optoelectronic layers to implement matrix-vector multiplications and rectified linear functions, respectively. The system is designed to be real-time and parallelized, utilizing arrays of light emitters and detectors connected with independent analog electronics. We experimentally demonstrate the operation of our system and compare its performance to a single-layer analog through simulations.

Constraint Bayesian optimization approach is used to optimize the beam pointing and spatial filtering of a laser beam using the capillary transmission and the output beam profile, as the optimization criteria. We have demonstrated that the developed method was able to robustly find the optimal laser parameters and it will be implemented in the SwissFEL UV photocathode laser in the future.

Encoded-diffraction hybrid systems—optical encoding and simple electronic decoding—offers feature distillation via model training. Additionally, the most faithfully reconstructed images are not the ones that are best classified. We parametrize our results with singular value decomposition (SVD) entropy, a proxy for image complexity.

Despite the breadth of scientific literature on micro- and nanoplastics (MNPs), a standardized procedure for detecting MNPs is still lacking so far, leading to incomparable results between published studies. This work innovatively proposed the combination of machine learning with advanced optical photothermal infrared (O-PTIR) spectroscopy to develop an efficient and reliable detection framework for MNPs. Spectra of MPs and non-MPs were first collected and inputted to build a classification model, based on which four important wavenumbers were selected. A simplified support vector machine (SVM) model was subsequently developed using the selected four wavenumbers. Good predictive ability was evidenced by a high accuracy of 0.9133. The developed method can improve speed as well as the reliability of results, having a great potential for routine analysis of MNPs, ultimately leading to the standardization of detection methods.

Evaluation of disease models is facilitated by live imaging which can be used to follow the behavior of the model during disease evolution, and when comparing before and after therapeutic intervention. When exploring in vitro samples for disease modeling in culture, there is a need for live, 3D, non invasive, real time, label free, subcellular resolution, dynamic, longitudinal imaging, which is currently lacking from the microscopy toolkit. Dynamic full field optical coherence tomography meets these needs and shows promise as a next generation tool for 3D live microscopy. Full-field optical coherence tomography is an interferometric technique to image transverse planes inside a sample in one shot, thus allowing distortionless rapid en face and volumetric imaging. Dynamic full field OCT is an evolution of full field OCT, where a series of frames is collected by the camera and the contrast generated by natural movements of subcellular organelles within the sample is revealed. Here, we present a new dynamic full field OCT module that may be interfaced to commercial microscopes, designed for use by biologists for long term applications in culture conditions. We present its application to models of disease in 2D and 3D samples.

A low-powered, non-invasive digital holographic microscopic imaging technique for embryo quality assessment is presented. Two groups of 2 cell-stage embryos cultured in media of different lipid concentrations have been characterized with digital holographic microscopy for lipid aggregation. The study suggests refractive index measurements are reflective of the lipid and dry mass content in embryos thus making DHM a prospective label-free diagnostic tool for quality assessments in assisted reproduction.

It has recently been discovered that biological live cells can behave like optical microlenses.

This has opened a new path towards future disruptive scenarios with the possibility of using such biolenses for the next technological developments in optics and photonics. Live cells can be employed and exploited as optical components for incredible applications ranging from simple imaging, to soft matter manipulation and biomedical diagnosis. In fact, the optical properties of such biological lenses can reveal new biomarkers useful for medical diagnosis. Different examples of application of biolenses will be illustrated and discussed. Furthermore, a new perspective for engineering biolenses to tailor their photonic properties will also be presented. Furthermore, it will be demonstrated that in-flow staining-free cytotomography based on digital holography allows for a complete and accurate 3D characterization of biolenses.

Whether host phenotypic alterations induced by parasites are reversible or not is a core issue to understand underlying mechanisms as well as the fitness costs of infection and recovery to the host. Clearing infection is an essential step to address this issue, which turns out to be challenging with endoparasites of large size relative to that of their host. Here, we took advantage of the lethality, contactless and versatility of high-energy laser beam to design such tool, using thorny-headed worms and their amphipod intermediate host as a model system. We show that laser-based de-parasitization can be achieved using blue laser targeting carotenoid pigments in Polymorphus minutus but not in the larger and less pigmented Pomphorhynchus tereticollis. Using DNA degradation to establish parasite death, we found that 80% P. minutus died from within-host laser exposure. Survival rate of infected gammarids to laser treatment was higher than uninfected ones. The failure to kill P. tereticollis was also observed with nanosecond-green laser, an alternative laser source targeting lipid. We discuss the possible causes of amphipod death following parasite treatment and highlight the perspectives that this technology offers.

At Zero Point Motion we create low noise chipscale optical inertial sensors by combining photonic integrated circuit (PIC) structures with micro-electro-mechanical systems (MEMS) mechanical structures. Our technology is derived from cavity optomechanics which uses the coupling between optical resonances and mechanical motion to detect picometer to femtometre displacements, producing lower noise readout compared with capacitive devices. Our platform comprises ring resonators with whispering gallery mode resonances, that are evanescently coupled to the motion of MEMS accelerometer and vibratory gyroscope test-mass. We report on progress in realising an integrated device, with both MEMS and PIC structures die-to-die bonded and then packaged with light sources and detectors on-chip.

Here, we report on a CMOS-compatible thulium-doped high power continuous wave (CW) optical amplifier, leveraging large mode-area gain waveguides. The amplifier structure combines a silicon nitride waveguide

above which a sputtered 1250 nm-thick thulium-doped alumina gain layer is deposited. We demonstrate > 220 mW output signal power at center wavelength of 1850 nm inside a 9-cm-long amplifier. Small signal gain of > 15 dB is achieved.

We propose a novel polarization rotator concept using two-dimensional (2D) anisotropic materials, such as molybdenum trioxide, on top of 3 µm silicon waveguides. The in-plane anisotropic behavior of 500 nm thick MoO3 flake is analyzed and confirmed with Raman spectroscopy.

Silicon waveguides are a promising candidate for integrated nonlinear optics applications. Nonlinear coefficients of Silicon on Insulator (SOI) waveguides have been previously measured using techniques such as Z-scan, D-scan, Four Wave Mixing (FWM) and Self-phase modulation. However, they have several drawbacks such as they operate at high power or are cumbersome to setup and require multiple measurements to determine all the coefficients. In this work, we develop a direct and single measurement technique to characterize the nonlinear processes in SOI waveguides. This is achieved by employing a heterodyne interferometric technique to accurately measure minute nonlinear response. The measured nonlinear amplitude and phase shifts at 1550 nm wavelength are fit to extract third-order nonlinear coefficients of Two-photon absorption, Kerr nonlinear index, Free carrier absorption and Free carrier dispersion. The obtained coefficients for SOI waveguides are close to that found in literature measured using the above mentioned techniques. The advantages of this method include easy interpretation of the output signal and relatively low power of operation. It is especially advantageous for studying materials such as Phase Change Materials (PCM) in which phase changes occur dynamically. This aspect is quite promising for characterizing emerging materials for integrated photonics applications.

Ray-wave correspondence has proven a powerful tool in mesoscopic optics, in particular in the description of deformed microdisc cavities with a versatile application potential ranging from microlasers to sensors. New material classes such as graphene-based systems have enriched the field by adding Dirac Fermion optics as well as anisotropic material properties as further system parameters. The trigonally warped dispersion relation in bilayer-graphene billiards generalizes the concept of birefringence and opens unconventional ways of trajectory control in the interplay of dispersion relation and the cavity geometry as we illustrate in this contribution.

Photonic quantum technologies are a promising platform for a large variety of applications ranging

from secure long-distance communications to the simulation of complex phenomena. Among the material

platforms under study, semiconductors offer a wide range of functionalities opening several opportunities for

the development of integrated quantum photonic circuits. AlGaAs is particularly attractive to monolithically

integrate active and passive components since it combines high second order nonlinearity, electro-optic effect

and direct bandgap. In this talk, I will present the work of our team on the generation of quantum states of

light in the telecom range with nonlinear AlGaAs chips working at room temperature.

Memristive devices are an emerging new type of devices operating at the scale of a few or even single atoms. They largely exploited for emulating the electrical function of synapses and are thus currently investigated for performing in-memory and neuromorphic computing. In this contribution, we report the observation of a novel feature in these devices. We show that memristors can also emit photons during their activity. We identified three mechanisms producing photons with vastly different properties. The crossover between emission regimes depends on the history of the memristor and its operating conductance. Our results suggests that this new generation of memristor pave the way for multidimensional neural networks using both electrons and photons as information carrier.

Femtosecond pump and probe optical spectroscopy has been employed for investigating ultrafast cooling of metal and carbon nano-objects, leading to quantitative determination of the physical parameters ruling thermal exchanges, such as thermal boundary resistance and thermal conductivity. Experimental and theoretical investigations on plasmonic nanoparticles and carbon nanotubes will be reviewed, as well as their applications to photoacoustics.

Silicon nanowires (Si NWs) represent one of the most promising platforms to be integrated into modern nanodevices. The fabrication of a dense array of vertically aligned ultrathin Si NWs using a low-cost, maskless approach and compatible with Si technology will be here demonstrated. Si NWs with efficient light emission at room temperature (RT) represent a great advance industry, paving the way for a wide range of unexpected photonic applications. In this work I will show the realization of a new hybrid material based on the luminescence of Si NWs and two different dyes for light-harvesting antennas applications, without any surface functionalization and with energy transfer efficiencies higher than 90%. The luminescence of Si NWs has also been used for sensing applications by the realization of highly sensitive sensors for the detecting of low concentrations of toxic gases. These sensors allow the detection of toxic gases below the threshold limits for human health, through both optical and electrical transduction. The achievement of light emission from silicon-based materials represents a revolution in the industrial field, as it paves the way for new Si applications.

In this work, we present the first experimental results on a Schottky photodetector based on Silicon Carbide (SiC) and Graphene (Gr) designed to operate in the visible spectral range. While SiC has been extensively investigated for various applications in the ultraviolet domain, there are only a few works in the visible range, where SiC exhibits negligible optical absorption. To overcome such intrinsic limit of SiC, we exploit the properties of a single layer of Gr to enhance, significantly, the photodetection performance of the device operating, in our experiments, at the wavelength of λ=633 nm. From the current-voltage (I-V) characteristics, a series resistance of 3.7 kΩ, an ideality factor of 8.4, and the zero-bias Schottky barrier height of 0.755 eV have been calculated. Finally, the internal responsivity, as function of the reverse bias applied to the device, has been measured demonstrating a maximum value exceeding 1 mA/W at -5V.

You Two-dimensional nanomaterials, such as MoS2 nanosheets, have been attracting increasing

attention in cancer diagnosis and treatment, thanks to their peculiar physical and chemical properties.

Although the mechanisms which regulate the interaction between these nanomaterials and cells are not yet

completely understood, many studies have proved their efficient use in the photothermal treatment of cancer,

and the response to MoS2 nanosheets at the single-cell level is less investigated. Clearly, this information can

help in shedding light on the subtle cellular mechanisms ruling the interaction of this 2D material with cells

and, eventually, to its cytotoxicity. Here, as a first presented biomedical application of nanomaterials, we use

confocal micro-Raman spectroscopy to reconstruct the thermal map of single human cancer cells targeted

with MoS2 under continuous laser irradiation. The experiment is performed by analyzing the water O-H

stretching band around 3,400 cm−1 whose tetrahedral structure is sensitive to the molecular environment and

temperature. Compared to fluorescence-based approaches, this Raman-based strategy for temperature

measurement does not suffer fluorophore instability, which can be significant under continuous laser

irradiation. As a second biomedical application, we focus on preliminary obtained by the fabrication and use

of magnetic nanomaterials in Magnetic Resonance Imaging, tested on 3D-printed phantoms.

We present our recent theoretical and experimental advancements in studying complex multiple nonlinear interactions of coherent solitary wave structures on unstable background -- breathers. We use the focusing one-dimensional nonlinear Schrödinger equation (NLSE) as a theoretical model. First, we describe the nonlinear mutual interactions between a pair of co-propagative breathers called breather molecules. Then with the novel approach of breather interaction management, we adjust the initial positions and phases of several breathers to observe various desired wave states at controllable moments of evolution. Our experiments carried out on a light wave platform with a nearly conservative optical fiber system accurately reproduce the predicted dynamics. In addition, we consider generalizations of the scalar breathers theory to the vector two-component NLSE describing polarized light and show examples of resonance vector breathers transformations.

We deploy a neural network to predict the spectro-temporal evolution of simple sinusoidal temporal modulations upon propagation in a nonlinear dispersive fibre. Thanks to the speed of the neural network, we can efficiently scan the input parameter space for the generation of on-demand frequency combs or the occurrence of substantial spectral/temporal focusing.

A nonlinear interaction of waves in a dispersive medium manifests itself in a four-wave mixing process that can be described as an evolution of waves’ parameters on a phase plane in a form of closed orbits. Here we propose a method to control these trajectories and to switch from one state to another in an optimal manner by implementing an abrupt change of the average power. The method is confirmed experimentally by the reconstruction of a fundamental four-wave mixing dynamics in an idealized model using iterative propagation in a short segment of fiber.

We present in this work a study of 4-field symmetry breakings in two photonic molecule structures consisting of two identical microresonators with distinct coupling arrangements. Mediated by the Kerr-interaction, the systems also display different 2-field symmetry breakings, periodic switching and chaos. The wide range of nonlinear optical dynamics makes the system ideal for all-optical switching, optical memories, telecommunication systems, polarization controllers and integrated photonic sensors.

We have implemented of a light pulse atom interferometer based on the diffraction of free-falling atoms of Rubidium by a picosecond frequency-comb laser. We have studied the impact of the pulses' length as well as of the interrogation time on the contrast of the fringes. Our data are well reproduce by a theoretical model based on the effective coupling which depend on the overlap between the pulses and the atoms. This technique, which we demonstrated in the visible spectrum on Rb atoms, paves the way for extending light-pulse interferometry to other spectral regions (deep-UV to X-UV) and therefore to new species, since one can benefit from the high peak intensity of the ultrashort pulses which makes nonlinear frequency conversion in crystals and gas targets more efficient.

This study investigates the use of Zinc Telluride (ZnTe) as a second-order nonlinear coating to enhance THz wave generation in silica nanofibers. Numerical simulations show that ZnTe coatings can significantly improve THz wave generation efficiency due to their large second-order nonlinear susceptibility and high transparency in the THz frequency range. Specifically, we observe a 2000-fold increase in THz wave generation efficiency with a 100nm thickness ZnTe coating compared to an uncoated silica nanofiber.