bluuebunny/crossref_metadata_2025 huggingface dataset:
New polishing concepts for optical components in flexible and efficient process chains
Authors: Bliedtner Jens , Faehnle Oliver , Henkel Sebastian , Schulze Christian , Frank Samson
Published: October 2024

The flexible and efficient production of precise optical free-form surfaces requires advanced kinematic operating principles. Due to the complex surface geometries, polishing processes with point or linear contact are used. These generally result in longer polishing times due to the smaller footprint compared to large-area polishing tools. The creation of a high precision, polishable surface in the shaping steps of the process chain is therefore of great importance. This applies in particular to minimising the roughness, but also the depth of SSD (sub-surface damage) and the mid-spatial frequency errors before the polishing process. The article describes selected process chains for the production of free-form optics and presents options for optimising the required polishing steps.
A perturbation method for the ray-transfer matrix of the crystalline lens
Authors: Barion Antonio , Mitra Koondanibha
Published: October 2024

Analytical expressions for the ray-transfer matrix have been proven useful for the understanding of ray propagation in gradient-index (GRIN) lenses. The determination of an exact analytical expression for the ray-transfer matrix of arbitrary GRIN lenses remains unsolved. We propose an approximation based on the perturbation method with highly accurate results for models of the crystalline lens, which outperforms existing methods.
Exploring the Potential of Chalcogenide Lens Designs for Cost-effective LWIR Systems
Authors: Liu Chang
Published: October 2024

The high cost of optical raw materials in the long wavelength infrared (LWIR) region necessitates the development of cost-effective solutions without compromising resolution. Chalcogenide glasses offer a faster and easier production process compared to growing single crystals of Germanium (Ge). Additionally, they can be molded into complex optical surfaces, reducing processing costs further for serial production. In this study, we explore the potential of chalcogenide lenses. Our comprehensive design study demonstrates that chalcogenide lens designs can achieve comparable or even superior optical performance with reasonable system complexity when compared to a wide-angle benchmark Ge design.
Generating function approach for freeform two-reflector two-target system
Authors: Braam Pieter , ten Thije Boonkkamp Jan , Anthonissen Martijn , IJzerman Wilbert
Published: October 2024

We discuss an inverse method to compute a freeform two-reflector two-target system. The optical path length constitutes an integral component and can be expressed in terms of position coordinates at the first target. The system is expressed in terms of a generating function, closed with energy balance and requires a sophisticated least-squares solver to compute the shapes of the reflectors. In a numerical example, we illustrate the algorithm’s capabilities to tackle even the most intricate light distributions.
Light Scattering of optical Components and their Imperfections: Measurement, Modelling, and System Analysis
Authors: Herffurth Tobias , Mühlig Christian , Munser Anne-Sophie , Schröder Sven
Published: October 2024

Light scattering in optical systems is caused by various imperfections such as surface roughness, bulk inhomogeneity, contamination, and ghost light beam paths. Control of these scattering sources is crucial, particularly for high-precision optical components, and involves both measurement and modelling from the design phase through fabrication to system integration. Recent developments at Fraunhofer IOF have led to advanced instruments for characterization of both optical components and system. Moreover Light scattering measurements provide not only analysis capabilities but also critical data for optimizing fabrication processes by identifying scattering contributors. Results and applications of these techniques and tools will be presented, highlighting their impact on optimizing optical system fabrication.
Mesh-Based Double-Sided Freeform Lens Optimization
Authors: Sun Yuou , Deng Bailin , Zhang Juyong
Published: October 2024

We present a mesh-based method for optimizing double-sided freeform lenses to control their caustic effects. Unlike traditional single-sided approaches, we optimize both sides of the lens simultaneously, using a bijective correspondence between the two sides to control light refraction paths. Our approach balances image fidelity, geometric compatibility, and physical constraints. Results demonstrate the method’s capability to accurately produce intricate light patterns, opening new possibilities in optical applications.
Surface characterization in fabrication environments using angle resolved light scattering: From roughness and defect analysis to in-situ coating inspection
Authors: Munser Anne-Sophie , Herffurth Tobias , Wyltschew Marius , Gischkat Thomas , Schröder Sven
Published: October 2024

The performance of an optical component or surface might quicky be limited by light scattering induced by the surface and coating roughness, as well as imperfections and contaminations. On the other hand, the scattered light contains valuable information about its source, which makes scattering based techniques powerful characterization tools for these important features. A major advantage is the fast, robust, and contact free measurement approach enabling even close-to process applications. Based on several examples we demonstrate the potential of light scattering characterization during the fabrication process up to even in-situ coating inspection.
Using Acoustic Emissions for an in-situ evaluation of the polishing process and its parameters
Authors: Benisch Michael , Fähnle Oliver , Bogner Werner
Published: October 2024

Mechanical chemical glass polishing is a complex process with mechanical and chemical interactions. While we have used Acoustic Emissions (AEs) already for basic measurements, we have researched the process and its parameters e.g., the density of the polishing slurry or the glass type for further investigation. We also have carried out crack tests on samples to investigate the crack mechanism. We suggest the further investigation of AEs to improve the above mentioned process and to prepare a transfer of this approach for further processes.
Bioluminescence biosensing platforms for One Health: From paper sensors to thread-based analytical devices
Authors: Michelini Elisa , Gregucci Denise , Nazir Faisal , Maiorano Emanuela , Calabretta Maria Maddalena
Published: October 2024

Bioluminescence is a fascinating phenomenon in which photons are emitted as byproduct of a chemical reaction occurring in living organisms, including bacteria, fireflies, and several marine species. Here we report the development of novel bioluminescent tools and strategies which can be used to improve the analytical performance of paper-based smartphone biosensors. In particular two new applications are reported based on paper and thread-based bioluminescent biosensors.
Analysis of imaging modalities for classification of tumoral vs. normal tissues using an FD-FLIM based MMF endoscopy probe
Authors: Fay Victoria , Tolstonog Genrich , Simon Christian , Psaltis Demetri , Moser Christophe
Published: October 2024

Current surgical resections for Head and Neck Cancers aim for clear margins to prevent local recurrence. However, up to 20% of cases result in positive margins, with secondary surgery increasing the chances of death after 5 years. We envision a MMF endoscope that collects high resolution images using wavefront shaping to scan a 405 nm beam at the fiber tip and collecting fluorescence intensity and lifetime to map tumor margins and detect residual malignant cells. To address the question whether the information contained in the fluorescence and morphology can be used to classify cancer and normal tissues, we used images acquired with a microscope and artificial neural network. Initial findings show promise to separate cancer from normal tissue when training neural networks on FLIM data. Spatial and temporal resolution and required field of view for effective margin assessment are determined.
Evolution of the optical scattering properties of blood plasma during clot formation
Authors: Abi Nassif Lea , Khater Wadih , Pellen Fabrice , Le Jeune Bernard , Abboud Marie , Espinasse Benjamin , Le Brun Guy
Published: October 2024

Venous thromboembolism (VTE) is a common and serious disease which encompasses deep vein thrombosis (DVT) and pulmonary embolism (PE). DVT is created when a blood clot forms in the deep veins of the leg and when the clot migrates through the bloodstream, to lung arteries, it creates a PE. VTE is the third cardiovascular cause of death overall and is responsible for 30000 annual deaths in Europe. After biological and clinical investigation, nearly half of VTE cases have no known origin (idiopathic VTE). Among the patients developing idiopathic VTE, about 30% of them would have a recurrent thromboembolic event, 70% would not be subjected to any recurrence. A balance must be struck between the risks of recurrent thrombosis if anticoagulant treatment is stopped versus the risks of bleeding associated with continued anticoagulation therapy that can go up to the course of decades. The search for new biomarkers allowing to best stear the treatment of patients is thus of major interest. Recent studies seem to link clot’s structure to a risk of recurrence. The aim of our work is to develop a sensitive optical method, in order to help with VTE patient’s prognosis, measuring the evolution of the scattering coefficient of a plasma during ex vivo clot formation.
Polarization-resolved surface-enhanced sensing of single-stranded DNA with Bloch surface waves
Authors: Mogni Erika , Pellegrini Giovanni , Gil-Rostra Jorge , Yubero Francisco , Celebrano Michele , Finazzi Marco , Schmidt Katharina , Fossati Stefan , Biagioni Paolo , Dostálek Jakub
Published: October 2024

We describe a novel one-dimensional photonic crystal design allowing for the concurrent excitation of transverse-electric and transverse-magnetic Bloch surface waves, thus paving the way for polarization-resolved sensing experiments. We discuss its application for the surface-enhanced sensing of oriented DNA molecules through nanoscale birefringence measurements.
Raman and Polarization-sensitive digital holographic imaging for rapid and label-free prostate cancer diagnosis
Authors: Khadem Hossein , Ferrara Maria Antonietta , Mangini Maria , Luini Alberto , Coppola Giuseppe , De Luca Anna Chiara
Published: October 2024

In this study, we report the results of two non-invasive optical methods, Raman microscopy (RM) and polarization-sensitive digital holographic imaging (PSDHI), for distinguishing prostate cancer cells from healthy ones. RM reveals cancer cells metabolize glucose faster, storing it as fatty acids and cholesteryl esters in lipid droplets (LDs). On the other hand, PSDHI shows significant morphological changes in LDs in glucose-incubated cancer cells, including number, volume, and refractive index. High birefringence in cancer LDs under perpendicular polarizations was observed, enabling fast discrimination with over 90% accuracy. PSDHI results align closely with Raman microscopy, suggesting its potential as a promising, high-speed technique for cancer screening purposes.
Side-scattering spectroscopy of biological aggregates
Authors: Salajkova Zita , Barolo Lorenzo , Baiocco Paola , Ruzicka Barbara , Boffi Alberto , Ricco Vincenzo , Ruocco Giancarlo , Leonetti Marco
Published: October 2024

In this study, we introduce a novel optical setup tailored for measuring scattering spectra of small biological aggregates with minimal sample volumes. Calibration was achieved using Polystyrene beads (PS beads) based on Mie scattering principles, enabling accurate measurements of scattering intensities. Bovine serum albumin (BSA) served as a model for studying protein aggregation due to its predictable aggregation behaviour at elevated temperatures. Analysis of non-aggregated and aggregated BSA solutions revealed significant differences in particle size, underscoring the setup's capability to detect variations in aggregation states. Key findings demonstrate the system's efficacy in monitoring protein aggregation processes, which is critical for biochemical and pharmaceutical research. The precise calibration method and the use of BSA as a validation tool highlight the setup's sensitivity and accuracy in quantifying changes in particle concentration and size due to aggregation. This study provides a framework for analysing protein aggregation and offers insights into the aggregation's impact on scattering properties.
Spatially resolved refractometry, fluorophore-concentration, axial-position, and orientational imaging using an evanescent Bessel beam
Authors: Szederkenyi Kaitlin , Julien Carine , Lagarde Bruno , Olevsko Ilya , Salomon Adi , Oheim Martin
Published: October 2024

Simultaneous field- and aperture-plane (back-focal plane, BFP) imaging enriches the information content of fluorescence microscopy. In addition to the usual density and concentration maps of sample-plane images, BFP images provide information on the surface proximity and orientation of molecular fluorophores. They also give access to the refractive index of the fluorophore-embedding medium. However, in the high-NA, wide-field detection geometry commonly used in single-molecule localisation microscopies, such measurements are averaged over all fluorophores present in the objective’s field of view, thus limiting spatial resolution and specificity. We here solve this problem and demonstrate how an oblique, variable-angle, coherent ring illumination can be used to generate a Bessel beam that - for supercritical excitation angles - produces an evanescent needle of light. Scanning the sample through the this evanescent needle enables us to acquire combined sample-plane and BFP images with sub-diffraction resolution and axial localisation precision. Background, resolution and polarisation considerations will be discussed.
Second harmonic Circular Dichroism in Achiral Nanostructures
Authors: Frizyuk Kristina , Nikitina Anastasia
Published: October 2024

We theoretically show that under circularly polarized plane wave or vortex beam illumination, the second-harmonic circular dichroism is possible even if the nanostructure is achiral. The interplay of nanostructure’s and crystalline lattice’s symmetries leads to specific conditions for observation of the circular dichroism, which can be expressed by a short formula. This can be particularly important for chiral sensing enhancement with nanostructure, where it is important to separate the signal from the nanostructure itself.
A convolutional neural network approach for multilayer analysis in infrared nanospectroscopy
Authors: Siebenkotten Dario , Kästner Bernd
Published: October 2024

The combination of Fourier-transform infrared spectroscopy and scattering-type scanning near-field optical microscopy allows for the spectroscopic investigation of materials and structures at the nanoscale, far below the diffraction limit in the infrared. This resolution is achieved by the use of metallized atomic force microscopy tips which locally illuminate the sample through the creation of near-fields at their apex. The complex interaction between incident light, a metallized tip and a layered sample necessitates the use of sophisticated models. While these models are powerful, using them to fit measured spectra is generally slow and often unstable, thus requiring expert oversight. Neural networks present a fast and often more stable alternative, but their application so far has focused on bulk samples. Here, we present the use of convolutional neural networks for the recovery of the optical and thickness properties from the spectra of samples consisting of one or two layers of polar crystals on silicon.
Advanced vibrational spectroscopy of magnetite nanoparticles
Authors: Sainz-Menchón Mireia , González de Arrieta Iñigo , Echániz Telmo , Nader Karam , Insausti Maite , López Gabriel A.
Published: October 2024

In this work, we discuss the challenges associated with measuring and interpreting the vibrational properties of nanomaterials at mid- and far-infrared frequencies, where vibrational bands are often broad and overlapping. This issue is compounded by the complex interaction between infrared light and particulate samples, which depends on packing density and particle connectivity. Preliminary results concerning the far-infrared optical properties of Fe3O4 nanoparticles have been obtained using the two most reliable methods (specular reflectance and attenuated total reflectance). These results are compared to one another and to their Raman counterparts. Finally, the influences of particle size and composition on the vibrational spectra are qualitatively discussed.
Investigation of random laser effect in structural disordered aperiodic multilayer
Authors: Falcone Pasquale , Moretti Luigi
Published: October 2024

The gap states of a random Fibonacci-on-average multilayer exhibit strong localization and high Q-factors, indicating potential suitability for random lasing applications. This study investigates the gain threshold behavior of random lasing within the visible spectrum. Using the scattering matrix method with complex refractive indices, our simulations examine the relationship between the gain threshold, structural disorder, and the number of layers. The results contribute to the understanding of random lasing behavior of this type of quasi-crystal.
Probing Dirac plasmon polaritons in bismuth selenide coupled nano-antennas by terahertz near-field microscopy
Authors: Schiattarella Chiara , Viti Leonardo , Sichert Lucia , Pistore Valentino , Wang Zhengtianye , Law Stephanie , Mitrofanov Oleg , Vitiello Miriam S.
Published: October 2024

The study of Dirac plasmon polaritons (DPPs) in two-dimensional materials has raised considerable interest in the last years for the development of tunable optical devices, plasmonic sensors, ultrafast absorbers, modulators, and switches. In particular, topological insulators (TIs) represent an ideal material platform by virtue of the plasmon polaritons sustained by the Dirac carriers in their surface states. However, tracking DPP propagation at terahertz (THz) frequencies, with wavelength much smaller than that of the free-space photons, represents a challenging task. Herein, we trace the propagation of DPPs in TI-based coupled antennas. We show how Bi2Se3 rectangular nano-antennas effectively confine DPPs propagation to one dimension, enhancing their visibility despite intrinsic attenuation. Furthermore, plasmon dispersion and loss properties of coupled antenna resonators, patterned at varying lengths and distances are experimentally determined using holographic near-field nano-imaging at different THz frequencies. Our study evidences modifications on the DPP wavelength along the single nano-antenna ascribable to the cross-talk between neighbouring elements. The results provide insights into DPPs characteristics, paving the way for the design of novel topological devices and metasurfaces by leveraging their directional propagation capabilities.
Refractometric sensing with plasmon resonances in dimer, trimer and quadrumer ensembles of gold nanoparticles
Authors: Toth Istvan , Farcau Cosmin
Published: October 2024

We studied by FDTD computer simulations the dependence of the surface plasmon resonances in linearly arranged gold nanospheres on incident light polarization, spheres number and diameter, and interparticle gap. The observed scattering spectra of large particles show a particularly interesting behaviour, with coupled plasmon resonances that can be either red or blue shifting with the modification of the interparticle gap. The sensitivity of the various observed coupled plasmon modes to refractive index variations is then evaluated.
Elucidating the photophysics behind the stimulated emission processes in CsPbBr3 nanocrystals films
Authors: Cerdán Luis , Milanese Stefania , De Giorgi Maria Luisa , Anni Marco , Bodnarchuk Maryna I.
Published: October 2024

Thanks to their excellent photoluminescence quantum yields, their facile and low-cost production, and their processing versatility, CsPbBr3 perovskite nanocrystals (NCs) stand out as excellent candidates to implement light-emitting devices. Elucidating their stimulated emission mechanisms is fundamental to achieve much more efficient and versatile perovskite lasers. In particular, two questions remain open: why the Amplified Spontaneous Emission (ASE) band is significantly shifted from the fluorescence one, and why the former seems to suddenly emerge from, and coexist with, the latter. These characteristic features have led to a debate, which is not settled yet, on which is the mechanism behind the ASE band shift. In this communication, we try to settle this debate and address these questions through experimental ASE measurements combined with numerical simulations. We show that the ASE behaviour in CsPbBr3 NCs thin films stems from a combination of reabsorption, excited state absorption, excitation of differently polarized waveguide modes, and the coexistence of short- and long-lived localized single excitons. The results in this work help understanding the stimulated emission mechanisms in perovskites and provide insightful information on research avenues to increase the efficiency of the light-emitting devices based on these materials.
Epitaxial LiNbO3 growth and layer transfer for thin-film electro-optic modulator realization
Authors: Larger Grégoire , Hauden Jerôme , Ecarnot Aurore , Pointel Anne-Laure , Astié Vincent , Bartasyte Ausrine
Published: October 2024

The aim of the PhD project is to develop a new trend in modulation system for Exail company: thin film (<1 μm) lithium niobate (LN) electro-optic modulator. It exhibits better performance in term of bandwidth, power consumption and footprint than legacy ones [1-3]. This PhD is a cooperation between Exail photonics which is world-renowned for the performances of their electro-optic modulators and FEMTO-ST institute which can offer the possibility to grow stoichiometric LN thin film by means of direct liquid injection metalorganic chemical vapor deposition (DLI-MOCVD). This cooperation opens the possibility to obtain industrialization of optical device based on CVD LN stoichiometric layers which allow to have enhanced performances such as higher electro-optic coefficient than that of congruent compositions of commercial single crystals. Thus, all steps from MOCVD layer deposition to modulator realization can be done here in Besançon.
Origin of extrinsic chirality in metasurfaces and nanoholes fabricated by nanosphere lithography
Authors: Petronijevic Emilija , Cesca Tiziana , Scian Carlo , Mattei Giovanni , Li Voti Roberto , Sibilia Concita , Belardini Alessandro
Published: October 2024

Nanosphere lithography is a cost- and time-efficient tool for the fabrication of various nanostructured materials. Multiple steps of metal layer deposition at different oblique angles were shown to produce complex asymmetric and chiral shapes. Here, we investigate samples in which polystyrene nanospheres are covered by Ag or combination of Ag and Au at a single step (under 45°). In this way, we obtain metasurfaces with asymmetric shells, with a nanohole array formed due to the shadowing effect. We investigate chiro-optical properties of four samples by exciting them in the 700-1000 nm range, at angles of incidence from -45° to +45°; we report on dissymmetry in the total extinction between left and right circularly polarized excitation gext, which follows the rules of extrinsic chirality. We then resolve the transmission of Ag metasurface in terms of hyperspectral Stokes parameters, and we connect the S3 parameter with gext. Finally, we characterize nanohole arrays obtained from the same samples when the nanospheres are removed; we further perform electromagnetic simulations to gain insight into the “egg” shaped nanohole.
Periodically-Poled Lithium Tantalate Ridge Waveguides for Efficient Nonlinear Frequency Conversion in the Near UV
Authors: Suntsov Sergiy , Sharma Chaitanya , Kretschmann Sarah , Hasse Kore , Kip Detlef
Published: October 2024

Optical damage resistant ridge waveguides for blue and near UV wavelengths have been fabricated using high-temperature Zr and Zn diffusion doping and vapor transport equilibration (VTE) of congruent LiTaO3 crystals. For both dopants high optical damage thresholds >10 MW/cm2 for 532 nm light were demonstrated at room temperature, which can be increased by a factor ~3 when heating the samples to ~150°C. Ridge waveguides with low optical losses of ~0.4 dB/cm were fabricated using diamond-blade dicing. First-order periodic poling with grating periods of ~3 μm can be used for efficient nonlinear frequency conversion for both SHG (800 nm pump) or SPDC (400 nm pump) processes.
Remote control of excitonic materials using coupled optical cavities
Authors: Pirruccio Giuseppe , García Jomaso Yesenia , Vargas Brenda , Ley Domínguez David , Armenta Rico Román , Sauceda Huziel , Ordóñez Romero César , Lara García Hugo , Camacho Guardian Arturo
Published: October 2024

Strong coupling with light has emerged as a powerful tool for modifying the properties of optical materials. Typical systems are based on a fluorescent layer embedded in a single optical cavity, whereby the excitonic emission is converted into a polarized, energy-tunable and dispersive polariton emission. There, excitons and photons coexist in the same volume and therefore any change in the emission properties of the excitonic material comes at the expense of simultaneously modifying the photonic environment where excitons reside, i.e., layer thickness and refractive index. Here, we demonstrate remote control over the intensity and total decay rate of the fluorescent layer by adding an extra purely photonic cavity strongly coupled to the first one. By modifying the resonant condition of the extra cavity, we reduce the total decay rate and suppress the fluorescence intensity of the fluorescent layer without explicitly affecting the first cavity. Such modification of the optical properties of the layer is the consequence of a resonant configuration that spatially segregates photons and excitons into different cavities.
Room-temperature photoinduced effects in elasticity and mechanical loss of GaAs for applications in high-precision optical metrology
Authors: Wagner Nico , Kroker Stefanie
Published: October 2024

Crystalline coating materials like AlGaAs/GaAs have the potential to revolutionise applications in high-precision optical metrology, such as ultra-stable laser cavities or gravitational wave interferometers. The primary driver for that is the promise of reduced noise and, thus, enhanced stability and measurement sensitivity. However, recent investigations revealed that the aspired noise level could be out of reach as an additional noise source is present, seemingly originating from intrinsic material properties and being related to the illumination of the material. To contribute to understanding this effect, we employ mechanical spectroscopy to explore the illumination-dependent mechanical loss of GaAs flexures at mechanical frequencies from 100 Hz to 94 kHz. The results indicate that photoinduced effects in bulk GaAs change the elasticity and mechanical loss with relaxation times of several minutes.
Type-I intermittency route to chaos in passively Q-switched Tm:YLF laser emitting at 2.3 μm
Authors: Dupont Hippolyte , Glasset Matthieu , Loiko Pavel , Georges Patrick , Druon Frédéric
Published: October 2024

We report on an original chaotic dynamic behaviour of a passively Q-switched 2.3-μm Thulium laser operating on the 3H4 → 3H5 transition. The experiment employs a Tm:LiYF4 laser crystal within various laser cavity configurations, involving optional additional cascade laser operation on the 3F4 → 3H6 transition at 1.9 μm. The saturable absorber employed is Cr2+:ZnSe, which is exclusively saturated by the 2.3 μm laser emission. A precise analysis of the Q-switching dynamics shows a pronounced inclination of the cascade laser scheme towards chaotic operation. To investigate the origins of chaos, we originally monitor the metastable 3F4 level population using cascade laser operation at 1.9 μm, which proves to be a crucial underlying parameter for explaining the observed instabilities. This analysis allows for explaining the specific dynamics of the Q-switched 2.3 μm Tm-laser intrinsically linked to Tm3+-doped materials. A very atypical route to chaos for a Q-switched laser is demonstrated involving type I intermittencies. The obtained results are of great interest for studying the premises of chaos in pulsed solid-state lasers.
Thermo-optical liquid-crystal phase modulator for ultrafast optics, driven by neural network
Authors: Jullien Aurélie , Ramousse Loic , Barland Stéphane , Femy Vincent , Cheriaux Gilles , Forget Nicolas , Claudet Cyrille
Published: October 2024

We propose a new spatial light modulator (SLM) concept, relying on a local thermal modification of a thick liquid crystal layer, that is optically-induced through the absorption of a control beam. This innovative thermo-optically addressed SLM, coined TOA-SLM, has shown dynamic phase control capabilities over multi-octave light spectrum, as a promising candidate for spatial or temporal manipulation of ultrafast pulses. In addition to being ultra-broadband and programmable, such a device is low-cost, large-aperture and un-segmented with a high number of control points. The construction and training of a neural network-based statistical model provides configurable design of a prototype TOA-SLM. This step, together with the ultra-broadband acceptance of the device and its ability to introduce continuous and deep phase modulation over a large aperture, opens the way for ultrafast laser aberration compensation using this new technology.
Multi-GW Peak Power Scaling in a Multi-pass Cell by Divided Pulse Scheme
Authors: Schygulla Henrik , Jimenez Nayla , Jiang Yujiao , Hartl Ingmar , Seidel Marcus
Published: October 2024

Multi-pass cells, known for their efficient spectral broadening, currently face a challenge in their peak power scalability. To address this, we implemented a strategy where the input pulse was split into 8 replicas, resulting in an increased pulse energy following nonlinear compression. The used laser delivered 208 fs pulses at 1030 nm, with pulse energies reaching up to 140μJ. Using 3 calcite crystals, the input pulse was divided and passed through the MPC, achieving a spectral broadening down to a 40 fs bandwidth limit. Subsequently, the replicas were recombined using an identical set of crystals and compressed via chirped mirrors. FROG measurements revealed a duration of 43 fs. The recombination losses amounted to less than 5 % of the output energy. This method is particularly attractive and cost-effective for spectral broadening of ultrafast lasers with adjustable repetition rate.
The phase of darkness – measuring the phase of a dark pulse
Authors: Brunzell Martin , Oxelmark Krook Christoffer , Laurell Fredrik , Pasiskevicius Valdas
Published: October 2024

Dark optical solitons are solutions to the nonlinear Schrödinger equation in normal dispersion media with positive Kerr nonlinearity, exhibiting a discrete π phase jump. These solitons are valuable to applications within telecommunication. Recent advancements have demonstrated the generation of two-colour bright-dark soliton pairs through cross-amplitude modulation in laser cavities, resulting in mode locking. In this study we present for the first time full field characterization of the electric field of a dark pulse. We achieved this by performing Blind Frequency Resolved Optical Gating measurements using the synchronous bright pulse as the gate pulse. The retrieved dark pulse verifies the existence of the expected π phase jump in the phase of the dark pulse, confirming theoretical predictions.
The role of crystal orientation in attosecond photoinjection dynamics in germanium
Authors: Talarico Matteo , Di Palo Nicola , Adamska Lyudmyla , Bonetti Simone , Inzani Giacomo , Arias Velasco Marta , Dolso Gian Luca , Borrego-Varillas Rocío , Nisoli Mauro , Pittalis Stefano , Rozzi Carlo Andrea , Lucchini Matteo
Published: October 2024

Ultrashort light pulses can be used to manipulate electronic and optical properties of solids at extreme temporal scales, paving the way to the study of ultrafast electron dynamics. In recent years, attosecond-based spectroscopic techniques have proved to be an instrumental tool in such studies. To this end, we investigated the effects of crystal orientation on ultrafast photoinjection dynamics in germanium using attosecond transient reflectance spectroscopy (ATRS) aided by time-dependent density functional theory (TD-DFT) calculations. Our results show that ATRS is sensitive to subtle changes in the transient reflectance due to crystal orientation, although carrier photoinjection in germanium is qualitatively robust against crystal rotation, displaying similar photoinjection processes and timings at two different crystal angles.
Ultrafast magnetic field induced by anisotropy in carbon nanotubes irradiated by intense laser fields
Authors: Zurrón-Cifuentes Óscar , Martín-Doménech Sergio , García-Cabrera Ana , Hernández-García Carlos , Plaja Luis
Published: October 2024

We report an unexpected result of the anisotropy of the nonlinear optical response of carbon nanotubes, inherent to their chirality. Using a model based on the resolution of the semiconductor Bloch equations, we theoretically demonstrate that, upon irradiation with an intense linearly polarized laser pulse along the axial direction, chiral nanotubes exhibit an oscillating azimuthal current that is absent in achiral species. This current induces a magnetic field parallel to the axis of the nanotube that radiates like a loop antenna.
Hybrid III-V/Silicon photonic circuits embedding generation and routing of entangled photon pairs
Authors: Lazzari Lorenzo , Schuhmann Jérémie , Lemaître Aristide , Amanti Maria I. , Boeuf Frédéric , Raineri Fabrice , Baboux Florent , Ducci Sara
Published: October 2024

Hybrid photonic devices, harnessing the advantages of multiple materials while mitigating their respective weaknesses, represent a promising solution to the effective on-chip integration of generation and manipulation of non-classical states of light encoding quantum information. We demonstrate a hybrid III-V/Silicon quantum photonic device combining the strong second-order nonlinearity and compliance with electrical pumping of the III-V semiconductor platform with the high maturity and CMOS compatibility of the silicon photonic platform. Our device embeds the spontaneous parametric down-conversion (SPDC) of photon pairs into an Al-GaAs source and their subsequent routing to a silicon-on-insulator circuitry. This enables the on-chip generation of broadband telecom photon pairs by type 0 and type 2 SPDC from the hybrid device, at room temperature and with strong rejection of the pump beam. Two-photon interference with 92% visibility proves the high energy-time entanglement quality characterizing the produced quantum state, thereby enabling a wide range of quantum information applications.
Solid and hollow whispering gallery mode resonators for all optical switch
Authors: Frigenti Gabriele , Murzina Tatyana V. , Farnesi Daniele , Pelli Stefano , Nunzi Conti Gualtiero , Soria Silvia
Published: October 2024

Whispering-gallery-modes resonators (WGMR) are effective switching devices when either coated or filled with non-linear material. We present examples of all-optical switching of hybrid WGM using polyfluorene, a methacrylate azobenzene and an acrylate derivates. We have studied the Kerr non-linear effect and thermal nonlinearities in a such hybrid systems.
Infrared and conductive properties of TCO films deposited by magnetron sputtering at different temperatures
Authors: Di Napoli Annalisa , Gaudino Eliana , Strazzullo Paolo , Farooq Umar , Musto Marilena , De Luca Daniela , Krammer Anna , Schueler Andreas , De Gennaro Emiliano , Russo Roberto
Published: October 2024

Low-emissive Transparent Conductive Oxide (TCO) coatings, such as Indium Tin Oxide (ITO) films, can be used to reduce radiative losses that affect Hybrid photovoltaic-thermal (PV-T) devices. This work shows the optical properties of ITO deposited by magnetron sputtering on a glass substrate with and without thermal heat treatment at different temperatures. All the analyses conducted include UV-VIS and infrared regions, up to 20 μm.
Photo-acoustic spectroscopy with widely tuneable laser enables circular dichroism mapping
Authors: Petronijevic Emilija , Skubisz Claudia , Seda Luca , Cesca Tiziana , Scian Carlo , Mattei Giovanni , Li Voti Roberto , Sibilia Concita , Belardini Alessandro
Published: October 2024

Sensitive and reliable characterization of chirality in nanostructures and molecules is of great importance in multidisciplinary research combining physics, chemistry and nanotechnology, with potential applications in pharmaceutical and agrochemical industry. Chirality is connected to circular dichroism (CD) - the absorption difference when the chiral medium is excited with circular polarizations of opposite handedness. Hence, measuring chirality by direct absorption measurements is of great interest in nanophotonics and plasmonics community, where the nanostructured media can enhance chiro-optical effects. Here we present a recently constructed photo-acoustic spectroscopy (PAS) set-up, which offers many degrees of freedom in characterization. We use a laser which is widely tuneable in the near-infrared (680-1080 nm) and visible (340-540 nm) ranges. The laser output is modulated with a mechanical chopper, where its frequency defines the penetration depth of the thermal signal. The input polarization is controlled by a linear polarizer and a quarter-wave plate, and the laser can be focused before impinging on the sample in the tightly closed photo-acoustic cell. The cell is placed on translational and rotational stages, which allows for the spatial mapping and extrinsic chirality measurements. Finally, a sensitive microphone measures the pressure changes in the cell, enabling scattering-free measurement of absorption and CD.
Novel Forward Brillouin Scattering measurement technique based on high-Q fiber ring resonator
Authors: Garrigues-Navarro Ana I. , Delgado-Pinar Martina , Díez Antonio , Andrés Miguel V.
Published: October 2024

The conventional detection of Forward Brillouin Scattering (FBS) in optical fibers requires of interferometric techniques using lengths of tens of meters. In this paper, we demonstrate an alternative approach that provides efficient and high-resolution detection of FBS signals, while using just a 20 cm length section of bare fiber. It consists of a pump and probe scheme using a fiber ring resonator as the interrogation system of the mechanical vibration, which modulates the resonances. The result is an amplitude modulated optical trace which allows the detection of resonances R0,m and TR2,m.
Applied Optics in the Development of Smart Road Markings
Authors: Lima Orlando , Rocha Segundo Iran , Reis Edson , Mazzoni Laura , Costa Manuel F.M. , Freitas Elisabete , Carneiro Joaquim
Published: October 2024

Road markings (RM) consist of two distinct layers: the paint layer and the retroreflective layer. Together, they function as system and are essential features for road safety. Recent studies have been centred on elevating these systems to a smarter level, imbuing them with novel functionalities, increasing their visibility, service life and road safety. These new capabilities encompass photoluminescence, anti-aging, self-cleaning, and thermochromism. The aim of this study is to review the advancements and highlight potential opportunities for RM, the materials employed, functionalization techniques, and the key outcomes achieved.
Terahertz waveform synthesis in scattering systems via nonlinear ghost imaging
Authors: Cecconi Vittorio , Kumar Vivek , Totero Gongora Juan Sebastian , Cutrona Antonio , Peters Luke , Olivieri Luana , Bertolotti Jacopo , Pasquazi Alessia , Peccianti Marco
Published: October 2024

Terahertz Nonlinear Ghost Imaging introduces a groundbreaking method for object sampling at spatial-temporal levels, achieving super-resolution (i.e., beyond the diffraction limit). Our theoretical and experimental endeavour seeks to leverage this technique, enabling arbitrary field-level waveform manipulation through intricate propagation in scattering environments. This approach facilitates essential agile waveform adjustment, made possible through near-field interactions between terahertz sources and scattering media.
Wavefront folding interferometer for single-shot lensless imaging
Authors: Halder Atri , Partancn Henri , Koivurova Matias
Published: October 2024

We have developed a fast, high-resolution, and single-shot lensless imaging technique based on the wavefront folding interferometer (WFI). Considering a stationary, quasimonochromatic, and quasihomoge-ncous source of light we studied the effect of spatial coherence on the retrieved image quality. Moreover, a thorough investigation of the resolution and the semi-infinity depth of focus of the imaging system was performed and demonstrated experimentally.
Exploiting SPDC of photons in polarization singular modes to generate heralded-single photons in remotely controlled topological classes
Authors: Corona-Aquino Samuel , Ibarra-Borja Zeferino , Calderòn-Losada Omar , Piccirillo Bruno , Vicuña-Hernández Verònica , Moctezuma-Quistian Tonatiuh , Cruz-Ramírez Hector , Lopez-Mago Dorilian , U’Ren Alfred B.
Published: October 2024

Polarization structured heralded single photons have been generated through spontaneous parametric down-conversion in a type-I dual crystal pumped by an inhomogeneously polarized beam in a general Poincaré mode, i.e. an inseparable superposition of two orthogonally polarized states through two orthogonal orbital angular momentum modes. The polarization structure of the signal photons can be controlled by manipulating the polarization state of their idler photon sisters with zero orbital angular. Due to the separate conservations of spin and orbital angular momenta in a type-I dual crystal SPDC process, any projection of the idler polarization state turns into a unitary transformation of the polarization basis of the signal photons, while preserving the orbital angular momentum modes originally included in the pump. We demonstrate, in this way, the ability to toggle between direct and basis-switched pump-single photon transfer by selectively projecting the polarization of the heralding photon before detection.
Bicolor Bessel beams generator based on single-mode fiber for STED system light source
Authors: Shao Luqing , Li Xijun , Qiu Min
Published: October 2024

In this paper, we have presented a novel and compact bicolor Bessel beams (bi-BBs) generator based on a single-mode fiber integrated with an axicon-like microstructure (AM). The proposed design utilized two Bessel beams manifested as pump beam of circular distribution at λ=405 nm and STED beam of donut distribution at λ=532 nm. Through numerical simulations, the influence of the AM size variance on the characteristics of bi-BBs was investigated and a type of AMs has been found to support STED beam. By controlling and optimizing the characteristics of bi-BBs emitted from a single-mode fiber greatly reduces the coaxial alignment difficulty of the free space STED systems and provides a new way to achieve mirrorless STED super-resolution systems.
Design of composite nanofibers for new all-solid state Raman wavelength converters
Authors: Bouhadida Maha , Azzoune Abderrahim , Dampt Théo , Divay Laurent , Fauvel Mathieu , Larat Christian , Beugnot Jean-Charles , Lebrun Sylvie
Published: October 2024

We present the design of composite optical nanofibers coated with different nonlinear materials (PMMA and TiO2) for the realization of new all-solid state Raman wavelength converters. Two coating processes, multilayer dip-coating and atomic layer deposition, have been successfully developed and optimized for the functionalization, inducing only relatively low losses comprised between 0.5 dB and 1.76 dB on 2 cm. Encapsulation has also been demonstrated. The Raman modal gain coefficients have been calculated to lie between 0.3 and 0.4 m-1W-1. Based on our previous results obtained with nanofibers immersed in different liquids, Raman threshold in the ns second regime should be obtained with few cm long nanofibers. This work opens the way to a new family of composite nanofibers for different applications in nonlinear optics.
SERS-based biosensors for the detection of human Thyroglobulin in liquid biopsies
Authors: Spaziani Sara , Quero Giuseppe , Managò Stefano , Zito Gianluigi , Terracciano Daniela , Macchia Paolo Emidio , Galeotti Francesco , Pisco Marco , De Luca Anna Chiara , Cusano Andrea
Published: October 2024

Here we have developed an advanced surface-enhanced Raman scattering (SERS) platform that enables the ultrasensitive, rapid and highly specific identification of tumour biomarkers in liquid biopsies. Our focus is on the detection of Thyroglobulin (Tg), the most important tumour biomarker for the diagnosis and prognosis of thyroid cancer. Specifically, SERS-active substrates fabricated by nanosphere lithography on chip or on tips of optical fiber (OF) were functionalised with Tg Capture antibodies. Gold nanoparticles were functionalized with Detection antibodies and conjugated with a Raman reporter. The sandwich assay platform was validated in the planar configuration and a detection limit of only 7 pg/ml was successfully achieved. A careful morphological characterisation of the SERS substrates allowed us to strictly correlate the coverage area with the Tg concentration. The same approach was successfully demonstrated in the washout of fine needle aspiration biopsies from cancer patients. The strategy was transferred to the Lab On Fiber (LOF) SERS platform and successfully used to detect Tg concentration. The proposed SERS-enhanced immunoassay platform has proven to be highly versatile and can be used with both microfluidic chip POC devices and SERS-OF-based optrodes to perform sensitive, specific and rapid ex vivo assays for Tg detection in liquid intraoperative biopsies.
Study of self-heated tapered silica microfibers by laser in air
Authors: Liss Ludivine , Abdedou Yanis , Weng Ruiling , Jeunesse Pierre , Hecquet Christophe , Nogrette Florence , Delaye Philippe , Besbes Mondher , Salvi Jérôme , Beugnot Jean-Charles , Lebrun Sylvie
Published: October 2024

We present measurements of the temperature of optical microfibers self-heated by a cw laser emitting at 1.48 μm. The experimental method we have implemented is simple and enables to perform for the first time to our knowledge spatially distributed measurements along the tapers and the microfiber part. Temperature rise of more than 20 °C is measured for moderate powers (200 mW) and relatively large radii (1.45 μm). The results are confronted to a numerical model we have developed and enable to determine range of values for the couple thermal transfer coefficient/surface absorption coefficient.
Deployment Integration Strategy for Daytime Radiative Cooling Materials: A Comparative Numerical Analysis of Roof Cooling and Water-Cooling Panels
Authors: Zghaib Peter , Es-Saidi Soukaina , Ortego Egoï , Abou Rached Ghady , Zoughaib Assaad
Published: October 2024

Daytime radiative cooling has emerged as a promising solution for continuous passive cooling. While significant progress has been made in material developments, questions persist regarding the potential large-scale deployment of this technology. Among the potential applications, two predominant uses of daytime radiative cooling materials arc under study: passive roof cooling and water-cooling panels. In the present study, a numerical assessment to compare the benefits of both integration schemes for passive daytime radiative cooling materials is conducted. These findings suggest adjusted approaches based on climatic considerations for the optimal deployment of daytime radiative cooling technologies worldwide.