Conference Agenda

There are many fields, such as microfluidics and Organ-on-a-chip technologies, where an optimal setting and control of temperature is necessary. These fields are reaching the forefront of personalised medicine, thus requiring developing more complex systems to adequately mimic any biological condition. On this work we propose the design and fabrication of a microfluidic chip mixing Polydimethylsiloxane (PDMS) and magnetic nanoparticles (MNPs) to obtain a device whose temperature could be adjusted by means of magnetic hyperthermia. Characterization of the device was performed with confocal microscopy and microcomputed tomography (micro-CT). Magnetic hyperthermia was employed to estimate the heating curve of the devices and Computational Fluid Dynamics (CFD) simulations enabled to analyse the heat distribution within the device when introducing flow.

Differential Absorption Lidar (DiAL) method is widely used for a number of ground-based and airborne greenhouse gas measurement applications. However, for a direct detection in the 2µm range, other sources of random noise can be neglected in front of the detection noise which increases with ranging. We therefore propose to evaluate the effect of non-constant Scheimpflug-like averaging to reduce the signal-to-noise ratio along the line of sight, during a 5-hour measurement campaign in the Paris region.

This work describes the development and testing of a diagnostic technique, based on a robust setup named Point Diffraction Interferometer, to characterize the wavefronts generated by metalenses. The presented optical setup is simple, cheap and insensitive to mechanical disturbances, nevertheless precisely capable to reconstruct the radiation wavefront produced by a metalens. The obtained interference patterns exhibit suitable contrast ratio of the fringes and high spatial resolution, thus allowing the detection of even highly distorted wavefronts, and providing a measurable information about the metalens properties.

To improve the efficiency of lens blocking for grinding and polishing, plaster use was studied in the work herein reported.The dimensional stability, low thermal expansion, shapability, and cost-effectiveness of plaster can contribute to the production of high-quality optical lenses. These results foster advancements in optical manufacturing, enhancing the simultaneous processing of multiple lenses or prisms.

The further development of optical lens production is a continuous optimisation process to improve results and shorten processing times. One approach to this is the adaptation of CNC programmes to produce rotationally symmetrical spherical lenses, as well as processing with additive manufactured tools as an ultra-fine grinding step. This can enable high surface qualities with Rq roughness around 100 nm and lower.

This study approaches to turn subjective influencing factors of CNC polishing into more deterministic ones by using cerium oxide foils in a similar way to CNC grinding tools. Due to the high cerium oxide concentration of those foils, coolant lubrication is sufficient without the need of a polishing slurry, enabling polishing processes on CNC grinding machines. A surface roughness Sq ≤ 50nm could be achieved.

Holographic multimode fibre endoscopes have established themselves as a tool for minimally invasive imaging, with particularly promising applications in the domains of neurobiology. These instruments allow imaging of previously inaccessible deep brain regions of living animals models. In all these applications, wavefront shaping is used to holographically control the input light fields entering the multimode fibre, with it being treated purely as a complex medium. Yet, multimode fibres exhibit symmetries and strong input-output field correlations, which are distinct for step-index and graded-index multimode fibres. In this work, we appropriately leverage these correlations to enable high-quality focussing of pulsed lasers with minimal intermodal dispersion. Such effect is then used as the underlaying basis for delivering pulsed super-resolution STED microscopy through a custom multimode fibre endoscope comprising input-output correlations of both step-index and graded-index fibre types. We show resolution improvements over 3-fold beyond the diffraction limit and showcase its applicability to bio-imaging. This work offers a solution for delivering short pulses through step-index segments and represents a step towards enabling advanced imaging techniques with virtually no depth limitation.

Lensless endoscopy enables minimally invasive imaging of biological tissues, particularly in the brain. However, miniaturization and optical performance remain key challenges. Multicore fibers (MCFs) are promising probes, where beam shaping at the output is typically achieved using Spatial Light Modulators (SLMs) at the input. Even though SLMs are active components, they require bulky optical elements and have efficiency and speed limitations.

Metasurfaces offer a compact alternative for wavefront shaping. By integrating them with MCFs, we aim to create a highly flexible two-photon endoscope. Metasurfaces can perform phase and group delay compensation with improved resolution while significantly reducing system footprint, as they match the fiber’s dimensions.

We characterize fiber transmission and metasurface performance. First, we measure the fiber’s transmission matrix, determine the required curvature for focusing, and fabricate the metasurface via lithography and etching. After fabrication, phase and transmission measurements validate its optical response. The metasurface is then imaged at the fiber input to realise the focusing at the output.

Our demonstration features a scanning endoscope using a passive metasurface for phase compensa-tion and focal spot generation, with beam scanning controlled by galvo mirrors. Finally, we discuss future prospects, including group delay compensation and active metasurfaces for dynamic wave-front control.

We propose a new spectroscopy technique in the mid-infrared (MIR) domain without any cryogenic system. The MIR field emitted by the source is shifted to the near-infrared using sum-frequency generation in a Periodically Poled Lithium Niobate ridge waveguide, and is then detected in the photon-counting regime using a low-noise SiAPD detector. The non-linear process is powered by a continuously tunable pump laser. We present here an experimental proof-of-concept, where the light emitted by a thermal source in the 3-4μm band is spectrally modulated using a Michelson interferometer. By continuously tuning the pump laser wavelength between 1058nm and 1078nm, the MIR spectrum is reconstructed, and the imposed spectral modulation period is retrieved successfully with a relative error of less than 5%

In this work, we present a novel approach to determine the refractive index n and the extinction coefficient κ from terahertz time-domain spectroscopy (THz-TDS) measurements using artificial neural networks (ANNs). We train the network in our experimental datasets to create a model that can accurately and efficiently calculate these material properties, the proposed neural network is superior to traditional analytical methods, which rely on approximations, and a faster and easier alternative to iterative root-finding algorithms. Our results demonstrate that this machine learning methodology solves common issues in THz-TDS data analysis, such as phase unwrapping, time-domain windowing, low computation rates, and high accuracy at low-frequency regions, effectively and achieve results with high accuracy.

Crude oils extracted from Kuwait oil wells were investigated using Far-infrared Transform Spectroscopy technique and compared to quantum chemistry calculation. Experimental data showed absorption peaks at 198 cm-1, 254 cm-1, 429 cm-1, and 528 cm-1. On the other hand, the calculated spectral bands of several alkane molecules were found near the experimental absorption bands that different level of calculation revealed more accurate assignment. Although only two bands were predicted by the calculation, adding alkane molecules of different lengths (pentane to decane) resulted in the formation of new bands. These preliminary results suggest that there is a mixture of different alkanes present in the investigated samples, a typical characteristic of unprocessed crude oil.

Accurate displacement measurement is critical in areas such as structural health monitoring, bioengineering, and industrial or high-radiation environments. Optical fiber microdisplacement sensors offer significant advantages for these applications, including high precision, reliability, compact size, and flexibility. Their ability to operate under extreme conditions such as elevated temperatures, corrosive atmospheres, or high-pressure environments makes them ideal for integration into complex or confined systems.

This work presents the experimental analysis of single-mode optical fibers (SMFs) modified with transverse through-hole microchannels, fabricated using femtosecond laser processing combined with ultrafast laser-assisted etching. These structures have been experimentally demonstrated as micro-displacement sensing devices.

Pulsed laser synthesis (PLS) of nanomaterials in liquids is a promising technique for synthesizing high-purity nanoparticles. However, its industrial scalability is limited by low production rates. This contribution discusses strategies to enhance nanoparticle yield as accurate control of the temporal dispersion and spatial beam shaping. Additionally, we explore applications of PLS-derived nanoparticles.

3D Stereolithography (SLA) technologies have emerged as a novel methodology to create a wide range of structures in the millimetric scale. Nevertheless, advancements in fields such as microfluidics or medicine rely on the creation of structures featuring micrometric resolution. SLA encounters resolution limits when printing objects within this range of sizes, especially when requiring hollow structures. On its side, femtosecond (fs) laser ablation emerges as a technique overcoming these limitations. The non-linear phenomena involved in the fs laser-matter interaction enable to perform a neat and precise extraction of material, resulting in a laser writing featuring microns. We propose a hybrid approach combining SLA and fs laser ablation to create a multi chamber microfluidic chip where micrometric substructures enable an accurate confinement of the samples.

Green and blue lasers have seen increased use in manufacturing of copper. They offer great advantages compared to common IR lasers especially in additive manufacturing. We tested the feasibility of a low average power femtosecond lasers at a centre wavelength of 515nm for use in micron-precision additive manufacturing of copper particles. A laser beam with an average power of 4W in the near IR was used to achieve second harmonic generation, and the resulting green beam was used to melt copper particles with sizes between 30 and 50µm. Melting of the powder was achieved and small two-dimensional structures were created.

We present a novel near-infrared broadband, flat-top optical

frequency comb spanning 1.6 THz. This comb is generated using an

interband gain medium operated in an ultrafast gain recovery regime within

a unidirectional ring cavity. The remarkable stability of our approach is

evidenced by a 1 Hz RF linewidth. The injected RF signal not only governs

the spectral bandwidth and free spectral range but also tailors the comb’s

spectral shape—a feat achieved by simultaneously injecting multiple

modulation tones. This advanced level of control opens promising avenues

for applications in communication, sensing, and ranging, where precise and

stable frequency lines are essential for performance and reliability

Optical sensing exploiting plasmonics and other types of surface waves provides exceptional performance for chemical and biological detection due to its high sensitivity and real-time capabilities. This study explores the integration of thin films with plasmonic, specifically leveraging metallic and dielectric nano structures, fabricated through sputtering and colloidal synthesis techniques. Advanced surface wave excitations such as localized surface plasmon resonances (SPR), Tamm Plasmon Polaritons (TPP), Bloch surface waves, and surface plasmon polaritons (SPP) are used to amplify sensor performance. Simulations and experimental data show that these nanostructured coatings significantly enhance electromagnetic field confinement, leading to improved detection limits and sensor robustness, showcasing promising applications in environmental monitoring, gas detection, and biomedical diagnostics.

The range of applications using gold nanostructures for optical sensing increases rapidly, primarily utilizing the local surface plasmon resonance effect that increases the sensitivity. Among electrochemical and colloid chemical preparations, one of the most effective and widely used ways of preparing gold nanoparticles is sputtering or evaporation followed by thermal annealing. A broad range of recipes exists in the literature; however, the optimal parameters depend greatly on the initial thickness of the gold layer, the temperature profile, or the substrate material. We show that combinatorial preparation and in situ ellipsometry are powerful ways to optimize the amount of material and the temperature profile, respectively. We show that the sensitivity can be enhanced even more when ordered periodic gold nanostructures are used, one of the simplest forms of which is a gold grating. The limit of detection values for the ambient and overlayer were calculated using finite element optical simulations.

Achieving optimal wine quality depends on precise harvest timing, a traditionally laborious and subjective task. To address this challenge, this study proposes the integration of advanced sensing technologies. Proximal sensors, such as the Multiplex fluorescence sensor, and remote sensing via UAV-based imaging are combined to provide a comprehensive assessment of grape phenolic maturity. This integrated approach aims to deliver spatially explicit information, enabling accurate and efficient monitoring of grape quality and ultimately, optimizing wine production.

Aimed at enhancing the sensitivity, we develop an integrated optically pumped magnetometer (OPM) with the dual-beam scheme. Additionally, we explore the application of this sensor for magnetic particle detection and propose a method to estimate the rotation frequency of magnetic particles. Through experimental analysis, we establish a correlation between the rotation frequency and the flow rate, which enables the flow rate measurement.

This paper presents a novel optical-comb-based refractive index sensor that simultaneously achieves high-sensitivity and high-precision by combining THz-comb-based frequency multiplication with active-dummy temperature compensation in a dual-comb configuration. In this approach, a little RI-induced shift of the comb mode spacing (frep) is frequency-multiplied via THz frequency comb, while the dual-comb scheme compensates for temperature drift in frep. Experimental results demonstrate a 3100-fold improvement in RI sensitivity and a 10-fold enhancement in measurement precision.

In this work, a motionless method to achieve quantitative phase imaging in single-pixel microscopy based on the transport of intensity equation is presented. In this approach, a digital micromirror device is used to generate wide-field structured illumination over the sample. The light resulted by the interaction between the sequence of light patterns and the sample is collected using a bucket detector. The integration of a focus tunable lens allows the motionless acquisition of multiple intensity images required for applying the transport of intensity equation. Quantitative phase retrieval in active single-pixel microscopy is demonstrated by imaging calibrated pure-phase test targets.

Photonic circuits, engineered to couple optical modes according to a specific map, serve as processors for classical and quantum light. They can be employed for tasks like vector-matrix multiplications, unitary transformations, and nonlinear operations, forming the basis for application like quantum computing. Liquid-crystal meta-surfaces (LCMSs) have recently been employed for optical simulations of quantum walks (QWs), by coupling transverse light modes with the polarization degree of freedom. These can be modeled as patterned waveplates, whose optic-axis orientation angle is non-uniform in space. In general, the system’s size and complexity (number of LCMSs) grow with the simulated evolution, affecting its feasibility in quantum experiments due to optical losses. Based on [3], we present an implementation of a purely quantum photonic circuit for a two-photon quantum walk experiment using a spontaneous parametric down-conversion source with visibility > 95%. We perform up to 5-step walks, involving up to 30 modes.

While indirect optical geometry measurements do not rely on the optical characteristics of the target’s surface, they depend on the presence of the fluorescent particles in the surrounding medium. In order to overcome uncertainty limits due to the random particle distribution, a well-controlled single particle is applied using an optical tweezer. As a result, the surface of a transparent object is detected via a trapped silica particle to pave the way for more precise indirect optical geometry measurements and to make measurable what is difficult to measure with state-of-the-art direct optical principles.

This work discusses the full-field measurement and characterization of guided ultrasonic waves (GUWs) on technical surfaces. The measurement is realized by a lensless digital holography approach with stroboscopic coherent illumination. This approach ultimately yields the height distribution featuring the deformation caused by the GUWs, which is then statistically evaluated using the structure function. As a result, GUWs are captured single-shot and characterized regarding wavelength and amplitude.

We propose a precise method for measuring the rotation angle of the polarization plane using a polarization-holographic grating combined with a quarter-wave plate. This approach enables real-time measurements with high accuracy.

To reduce the computational load for Digital Image Correlation (DIC) measurement, this paper proposes a multi-level grid interpolation and motion characteristics analysis initial guess method. In an image, all subsets that need to be calculated are divided into multiple levels of grids. Based on the deformation parameters of low-level grid cells, the initial deformation parameters of higher-level grid cells can be estimated. In the image sequence of quasi-static material tests, the deformation parameters of the 0-level subsets in the next image can be estimated by analyzing the motion characteristics of those subsets. The proposed method is validated using images from the classic "DIC Challenge". The algorithm proposed in this paper can effectively improve the accuracy of overall initial value estimation, and improving the overall execution speed of the algorithm.

Superconducting Nanowire Single-Photon Detectors (SNSPDs) are well known for providing a combination of single-photon sensitivity, low jitter, and high efficiency. Their dynamic range is generally limited to detecting one photon per event, causing dynamic range issues. To mitigate this problem,we present time-gated SNSPD detectors. We showcase our work from simple schemes giving switch-off switch-on transition times of about from 100 ns and improving those to the sub-nanosecond range.

Superconducting Nanowire Single-Photon Detectors (SNSPDs) are well known for providing a combination of single-photon sensitivity, low jitter, and high efficiency.

We present our recent developments on fast-recovery and arrays of SNSPDs specifically tailored for optical communication applications. We perform a full characterization of the detectors and we show their performance on a table-top optical communication setup, emulating a deep space optical communication (DSOC) experiment. We measured data rates exceeding several hundred Megabits per second (Mbits) depending on the communication protocol conditions. These results demonstrate the suitability of this technology for optical communications.

The ITER Upper port Wide Angle Viewing System (UWAVS) is designed to use wall and plasma luminance detected by visible and MWIR cameras at high spatial resolution and frame rates to provide information on the divertor wall temperature and related operational parameters. The modular UWAVS optical system is divided into four subsystems: Front-End Optical Module looks directly at the divertor. Following, light traverses the Interspace Optics Tube and the Bio-shield Optical Labyrinth to the Back-End Optics and Cameras in the port cell. Here light is split in four different channels and imaged. Design is defined by environmental conditions and accessibility and has a strong influence in the alignment and tolerance methodology. The in-vessel subsystem must endure extreme environmental conditions, requiring tight manufacturing and alignment tolerances, while module position and tolerances are somewhat more relaxed. Analysis on alignment tolerances sensitivity and STOP (Structural-Thermal-Optical-Performance) was performed for each of the four UWAVS subsystems. Individual module tolerances and STOP analyses were integrated to obtain an evaluation on the full system performance. Results of the simulations suggest it is possible to build a complex optical system to transport light over the required distance of 21 meters in ITER , while maintaining imaging performance.

We introduce a tabletop high harmonic generation scatterometry technique to extract structural and material characteristics of periodic nanostructures. Grazing incidence reflection scatterometry enables fast and robust measurements of linewidth and groove height with 20 nm and 2 nm precision respectively, paving the way for ultrafast spectroscopy on layered heterostructures.

The study of cultural heritage (CH) objects benefits greatly from non-invasive techniques like hyperspectral imaging (HSI), which enables material identification and spatial mapping. Due to the heterogeneous composition of CH artifacts, combining complementary techniques is essential for comprehensive analysis. However, handling such high-dimensional datasets remains a challenge. We present a computational protocol that combines spatial and spectral dimensionality reduction to enable early-stage fusion and efficient analysis of fused data, through multivariate methods, with a focus on Uniform Manifold Approximation and Projection (UMAP). We introduce an open-source plugin for Napari viewer, which allows for UMAP-based exploration of fused multimodal datasets. Our approach is demonstrated in case studies involving reflectance and photoluminescence data fusion, showcasing its effectiveness in detecting degradation phenomena and revealing material complexity in both plastic artifacts and historical paintings.

In line with the energy transition it is desirable to replace fossil fuels in the curing process of industrial powder coating. Infrared curing is an approved method for flat steel strip surfaces in the steel industry. However, powder coatings are often applied to complex geometries with cavities, where shading reduces the efficiency of infrared curing. IR-emitter arrangement in the reflective heating chamber, their geometry and the dwell time of the components are therefore crucial for a successful and efficient process. In addition, process optimization has to consider the optical parameter variation of the powder coating during the procedure to adjust the radiant power for different coatings and components. For that matter, measurements in the NAPUBEST prototype system are compared with optical simulations of the setup to get the simulation parameters in agreement with reality and thus provide a foundation for the design layout of industrial processes. For fast heating, in this investigating we chose short wave emitters.

Authors: Carlos Álvarez-Ocampo, Juan Julián-Barriel, Anna I. Garrigues-Navarro, Aleksander S. Paterno, Martina Delgado-Pinar, Antonio Díez, Jose Luis Cruz, Miguel V. Andrés

In the classical polarimetric solutions, the light polarization states generator (PSG) and analyzer (PSA) are placed on opposite sides of the medium. Such a solution is difficult to realized and even impossible for some media. An interesting alternative are configurations in which light passes through the PSG, the test medium and, after reflecting off the mirror, comes back again through the medium and the same module (PSG) acting as a PSA. This arrangement can be named one-way double pass Mueller polarimeter. Crucial to the system capabilities is the single module PSG/PSA design. This work verifies the possibility of using in them twisted nematic liquid crystals (TNLCs). There are noticeable differences in the quality of the polarimeter depending on the used components (linear polarizer with a single TNLC, two TNLCs or a combination of TNLCs with a liquid crystal variable retarder). Based on the measurement results, numerical models were created and optimized by minimizing condition number to find the best set of PSG/PSA configurations. The one-way double pass polarimetric systems were then tested in the laboratory. The results show that the use of TNLCs overcomes some measurement limitations and increases the system stability, compared to other solutions proposed in the literature.

This study explores the early detection of degradation in plastic-based cultural heritage objects using non-invasive spectroscopic techniques. The results on artificially aged ABS specimens revealed degradation markers at low exposure levels. Changes in polymer composition were then correlated with mechanical stiffening and increased friction. The approach offers valuable tools for in situ monitoring and preventive conservation of modern art and design objects.

The production of optical free-form surfaces requires a high level of precision and surface quality. The process chain presented combines pre-grinding, fine grinding and ultra-fine grinding using a 5-axis CNC machine in order to achieve high shape accuracy and surface quality. The presented process chain makes it possible to produce free-form surfaces with high geometric precision and optical qualities.

In recent years, non-Hermitian photonics has emerged as a prominent field, exploring open systems with complex eigenvalues. We propose simulating non-Hermitian dynamics via non-unitary photonic quantum walks, leveraging liquid-crystal technology for manipulating polarization and light amplitude.

to be announced

Filter-based spectral systems are highly competitive due to their compactness, simplicity, and well-defined spectral characteristics. However, their primary drawback remains low detection efficiency. This work explores various strategies to enhance detection efficiency. While an additional row of beamsplitters can significantly improve illumination, alternative folded beam path designs—eliminating the need for beamsplitters—prove to be far more effective. Additionally, a novel approach utilizing a freeform mirror is introduced, enabling differential adjustment of detection efficiency across different spectral regions. For the first time, a comprehensive comparison of these strategies is presented.

Exposure of the human skin to sunlight is essential for Vitamin D production. Due to our modern indoor lifestyle an increasing part of the population shows insufficient Vitamin D levels, especially in wintertime. Exposure to artificial UVB radiation can help in maintaining a sufficient Vitamin D level. The provided dose should be high enough to be effective, but low enough not to cause damage to skin or eyes. We designed a UVB module for integration in office luminaires that provides a very low UVB irradiance level that leads to an effective dose in a full working day. Ideally, the intensity distribution for a ceiling-mounted UVB module provides a uniform irradiance level on the face and hands of a sitting person. The final design is a balance between UVB LED availability, optical material use, manufacturing considerations, and required light distribution.

Urban Heat Islands (UHIs), aggravated by intense urbanisation and heat-retaining materials from buildings and roads, affect the thermal comfort of human beings. To mitigate this issue, this study aims to study the thermal performance of cement mortars with coaxial polymeric fibres produced by wet spinning and containing polyethylene glycol (PEG 600 and 1000) (CM_PCF) as phase change material. Samples were irradiated with a solar simulation lamp and monitored through infrared imaging and a thermometer. The CM_PCFs showed surface temperature reductions of up to 1°C. The results suggest that the phase change fibres can increase energy efficiency and support sustainable strategies for mitigating UHIS.

Laser-induced printing is an affordable, fast, and non-contact method for creating high-resolution images. Using plasmonic nanocomposite thin films, it enables the printing of color images with visual effects. However, the color gamut of these images is limited compared to inkjet printing. Therefore, it is necessary to optimize this gamut in order to print images that contain the widest range of colors and are closest to the original. There is currently no model to directly infer the color from the laser parameters used. Instead, a lookup table is required to associate these parameters with actual colors. Since colors vary depending on the type of sample used, it is essential to have a reliable method to quickly determine the laser parameters that produce the best colors. Two methods have been implemented to optimize the color gamut: a genetic algorithm approach to find colors that both increase both hue diversity and saturation, and a Bayesian approach to increase the size of the color gamut. Gamut mapping is then used to print the image, and the quality of the final printed image is assessed using metrics obtained from a psychophysical study.