HAL Portal IOGS (nstitut d'Optique Graduate School)
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Intraoperative Glioma Delineation with robust estimation of 5-ALA-Induced PpIX Contributions in Multiple-Wavelength Excitation Fluorescence Spectroscopy : Application on Clinical data
No full textInternational audienceDiffuse gliomas are challenging to remove due to indistinguishable tumor margins. This work focuses on tissue classification using fluorescence spectroscopy. A novel approach enhances classification accuracy, aiding in better differentiation of tumor and healthy tissues
Tailoring the visual appearance with correlated-disorder metasurfaces
No full textInternational audienceWe will review our current effort to model the resonance of individual resonators and collections of them with various theories, including quasinormal modes expansion and multiple scattering
Roadmap on Optics and Photonics for Security and Encryption
No full textInternational audienceIn 1994, Javidi and Horner published a paper in Optical Engineering that highlighted the ability of free space optical systems to manipulate sensitive data for authentication purposes. The underlying idea was effective yet surprisingly simple: an optical nonlinear joint transform using a random phase mask in both the input and the reference could produce a correlation peak to indicate whether the input object is authentic or not. This seminal paper fueled the development of this new discipline. After three decades, optical encryption and security have matured into a field that plays a central role in the development of photonics techniques. While the pioneering work was mainly focused on the field of optical information processing, nowadays, a broad spectrum of disciplines are contributing to developing security solutions, including nanotechnology, materials science, quantum information, and deep learning, just to cite a few. The present roadmap paper gathers 28 leading authors in the field from 21 academic institutions across nine different countries. It is organized into 17 sections which discuss the present and future challenges, state-of-the-art technology, and real-world solutions to address the security challenges facing our society
The Quantum-Efficiency Normalized Light Scattering Spectra of Colloidal Nanoparticles in Solution: Quantitative Comparison between Theory and Experiment
No full textInternational audienceLight scattering is an intrinsic property of colloidal nanoparticles and molecular assemblies in fluid or solid transparent media. Various measurable light scattering parameters may contribute to the characterization of colloidal systems. Herein, a quantitative, spectrallyresolved, steady-state light scattering technique is formulated and realized for the characterization of ensembles of colloidal nanoparticles in solution: quantum-efficiency normalized light scattering (QENLS) spectroscopy. QENLS spectra are complementary to standard ultraviolet-visible-near-infrared (UV-vis-NIR extinction spectra. Their measurement does not require knowledge of nanoparticle concentration, and they can be quantitatively compared to theoretical calculations. This is illustrated for archetypal plasmonic gold nanospheres, nanocubes and nanorods. We find good agreement between experimental and theoretical QENLS spectra for gold nanospheres and nanocubes, corroborated by results from the literature. Concerning gold nanorods, our QENLS results fall into the broad, somewhat disperse trends reported in the literature
Benchmarking direct and indirect dipolar spin-exchange interactions between two Rydberg atoms
No full textInternational audienceWe report on the experimental characterization of various types of spin-exchange interactions between two individual atoms, where pseudospin degrees of freedom are encoded in different Rydberg states. For the case of the direct dipole-dipole interaction between states of opposite parity, such as between nS and nP , we investigate the effects of positional disorder arising from the residual atomic motion on the coherence of spin-exchange oscillations. We then characterize an indirect dipolar spin exchange, i.e., the off-diagonal part of the van der Waals effective Hamiltonian that couples the states nS and (n + 1)S . Finally, we report on the observation of a new type of dipolar coupling, made resonant using addressable light shifts and involving four different Rydberg levels: this exchange process is akin to electrically induced Förster resonance, but featuring local control. It exhibits an angular dependence distinct from the usual -3 cos²(θ ) form of the resonant dipolar spin-exchange
Optimizing NN reduction in an atom interferometer network for GW detection
No full textInternational audienceThe sensitivity of an atom gradiometer aiming to detect gravitational waves (GW) is impacted by fluctuations of Earth's gravity field also called Newtonian Noise (NN). Sensor arrays have proved to be a promising technique for NN reduction. In our study, we further investigate the benefits of Atom Interferometer (AI) networks by improving their geometry and the extraction of the GW signal. We focus on Seismic Newtonian Noise in the frequency band from 0.1 to 10 Hz. On one hand, we show that using a specific detector geometry, a better NN rejection can occur optimizing the number of gradiometers in the network. On the other hand, we show that carrying out optimization in sub frequency bands - which results in using various detector geometries from a common network - allows even higher NN rejection while keeping a similar number of interferometers
Towards laser additive manufacturing of magnetic ferrite: processing of yttrium iron garnet and potential applications to electronic components
No full textInternational audienceThe potential of laser based additive manufacturing is investigated to prepare 3D ceramic magnetic pieces starting from powder of yttrium iron garnet (YIG) type ferrites. This preparation technique is demonstrated to be successfully applicable to produce YIG ceramic samples for studying their magnetic and structural properties. Deposition of YIG is performed on several different substrates and some experimental conditions discussed. X-ray diffraction characterization allowed to observe the influence of laser sintering on the composition of the ferrite. A relative magnetic permeability of about μr=44 is obtained for the produced prototype parts. Postdeposition heat treatment has been found to be efficient to improve the permeability of the printed ceramic. The performances of the laser manufactured ceramic parts have been tested in a wide frequency range up to 20 GHz, for different 2D or 3D devices such as magnetic core for toroidal inductor, waveguide isolator or coplanar isolators. Interestingly, non-reciprocal effect can be achieved at 12.4 GHz in a waveguide isolator and 10.8 GHz for a coplanar isolator. This study paves the way to an interesting manufacturing tech-nique with high potential enabling to prepare complex geometries for high performance devices operating at high frequency (radio and microwave frequencies)
Quasiannealed Monte Carlo method for light transport in strongly heterogeneous media
No full textInternational audienceRandom-walk Monte Carlo simulations are widely used to predict the optical properties of complex, disordered materials. In the presence of large heterogeneities (e.g., spatially extended nonscattering regions in a turbid environment), an explicit description of the microstructure and the macrostructure and of the light propagation therein is generally required, in addition to a statistical average over a representative set of microstructures, thereby making simulations in the so-called “quenched” disorder particularly time consuming. Here, we explore the possibility of modeling light transport in finite-size strongly heterogeneous media without an explicit description of the underlying microstructure but from the knowledge of typical random-walk trajectories in infinite-size media that take correlations between successive interaction events into account. Simulations may thus be performed for media of any macroscopic shape and size more efficiently. We illustrate this approach, coined “quasiannealed,” with the case of a two-phase emulsion consisting of transparent spherical droplets dispersed in a turbid medium. Good agreement with predictions from simulations in quenched disorder on the reflectance of a finite-thickness slab is found for a large set of microstructure properties and thicknesses with typical errors on the reflectance on the order of a percent
