HAL Portal IOGS (nstitut d'Optique Graduate School)
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A basic introduction to ultrastable optical cavities for laser stabilization
No full text10 pages, 8 figures, tutorial article to appear in Am. J . PhysInternational audienceWe give a simple introduction to the properties and use of ultrastable optical cavities, which are increasingly common in atomic and molecular physics laboratories for stabilizing the frequency of lasers to linewidths at the kHz level or below. Although the physics of Fabry-Perot interferometers is part of standard optics curricula, the specificities of ultrastable optical cavities, such as their high finesse, fixed length, and the need to operate under vacuum, can make their use appear relatively challenging to newcomers. Our aim in this work is to bridge the gap between generic knowledge about Fabry-Perot resonators and the specialized literature about ultrastable cavities. The intended audience includes students setting up an ultrastable cavity in a research laboratory for the first time and instructors designing advanced laboratory courses on optics and laser stabilization techniques
Assessment of polishing processes on sintered silicon carbide components produced by additive manufacturing
No full textInternational audienceSilicon carbide (SiC) is a commonly used technical ceramic in various fields such as energy and space mirrors applications. In recent years, additive manufacturing (AM) technologies have provided new fabrication opportunities for near-net-shape ceramic components which are of significant interest for the design of complex-shaped components for space mirrors. However, some of these technologies are still difficult to implement because of SiC properties such as UV light absorption and sintering difficulties. To consolidate AM SiC parts, silicon infiltration methods can be used to eliminate porosity and manufacture Reaction-Bonded SiC (RBSiC). At the moment, only AM extrusion methods such as Fused Filament Fabrication (FFF) offer the possibility to manufacture pressureless sintered SiC (SSiC). This study reports an evaluation of the manufacturing steps to obtain high quality SSiC components using the FFF process. Firstly, small structural components and 64 mm-diameter flat discs were 3D printed. After sintering, the resulting substrates reveal a fine microstructure with a high density. Polishing tests were carried out on disc samples using conventional polishing processes. Surface roughnesses were measured to 12 nm RMS and below 1 nm RMS after coating and polishing. In order to demonstrate the feasibility of printing off-axis and freeform geometries, some spherical shape components up to 160 mm-diameter were printed on a glass mould using a non-planar printing strategy. The first results confirm that this new manufacturing approach can be considered to reduce the number of manufacturing steps as well as costs and time for production of SSiC mirrors up to 200 mm-diameter
Ultrafast non-diffractive beams with tunable dispersion; opportunities for smart laser material processing
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Évaluation d'une architecture laser pour un microlidar troposphérique aérosols/vapeur d'eau
No full textInternational audienceNous décrivons la conception et l'évaluation d'une source compacte pour un microLiDAR à détection directe réalisant des mesures atmosphériques (aérosols, vapeur d'eau) au sol. L'architecture laser consiste en l'amplification d'une diode laser de grande pureté spectrale dans plusieurs amplificateurs fonctionnant en parallèle
2D and 3D nanomaterials-based metal oxide composites and their applications in gas sensing
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Unconventional Optical Imaging for Biology
No full textInternational audienceOptical imaging of biological systems has undergone spectacular development in recent years, producing a quantity and a quality of information that, just twenty years ago, could only be dreamed of by physicists, biologists and physicians.Unconventional imaging systems provide access to physical quantities –phase, absorption, optical index, the polarization property of a wave or the chemical composition of an object – not accessible to conventional measurement systems. To achieve this, these systems use special optical setups and specific digital image processing to reconstruct physical quantities. This field is also known as computational imaging.This book presents various non-conventional imaging modalities developed for the biomedical field: wave front analysis imaging, digital holography/tomography, optical nanoscopy, endoscopy and single-sensor imaging. Experimental setups and reconstruction algorithms are presented for each modality
Oxidation of metals during topographic functionalization upon ultrafast laser irradiation
No full textInternational audienceUltrafast laser-induced surface texturing became a well-recognized technique of surfacefunctionalization, with comparatively little work focused on the accompanying chemicalchanges. This paper reports a detailed investigation of the oxidation mechanisms induced onmetals in the form of pure metal and metallic glass.Ultrafast laser irradiation was performed in ambient and high vacuum conditions on tungstento generate so-called High Spatial Frequency Laser Induced Periodic Surface Structures(HSFL) with a sub- 100 nm period and sub-20 nm amplitude, as they are supposed to arise ina non-ablative regime. Scanning Transmission electron microscopy cross-sectional images,and x-ray photoelectron spectroscopy analyses reveal significant structural differencesbetween the laser-generated oxides and the oxides accumulated over time from ambientexposure [1]. The oxidation mechanism during ultrafast laser interaction was examined withthe help of Two Temperature Model and Molecular Dynamics simulations (TTM-MD)complemented by oxygen diffusion data, providing a predictive insight into the developmentof a thin oxide layer induced by the laser, a conclusion substantiated by the STEM images.This study is complemented by a detailed analysis of ultrafast laser irradiation of metallicglasses under conditions of generation in a one-step laser process of dense nanowell arrayswith dimensions down to 20 nm spontaneously formed in the ultrafast laser irradiation spot[2]. In addition to the topographic functionalization, the laser-irradiated amorphous materialexhibits structural changes analyzed by spectroscopic techniques at the nanoscale such asenergy-dispersive X-ray spectroscopy and electron energy loss spectroscopy. Results revealstructural changes consisting of nanocrystals of monoclinic zirconia that grow within theamorphous ZrCu matrix. The mechanism is highlighted by an atomistic simulation of thelaser-induced nanowell formation.References:[1] P. Dominic, D. Iabbaden, F. Bourquard, S. Reynaud, A. Nakhoul, A. Weck, J.-P. Colombier, F.Garrelie, ‘Unveiling nature and consequences of tungsten oxidation upon ultrafast laser irradiation’,Applied Surface Science 655 (2024) 159580 (doi.org/10.1016/j.apsusc.2024.159580[2] M. Prudent, D. Iabbaden, F. Bourquard, S. Reynaud, Y. Lefkir, A. Borroto, J.-F. Pierson, F.Garrelie, J.-P. Colombier, ‘High-Density Nanowells Formation in Ultrafast Laser-Irradiated Thin FilmMetallic Glass’, Nano-Micro Lett. (2022) 14:103 (doi.org/10.1007/s40820-022-00850-4
14 MeV and Atmospheric Neutron Monitoring Through Optical Fiber Dosimeters
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Prediction of Wetting Behaviours of Femtosecond Laser Texturized Surfaces
No full textInternational audienceIt is well known that surface topography modification can be used to tune and control surface wettability, and femtosecond laser ablation can be applied to modify a surface's topography with ultimate precision. However, it is not so well known how to predict surface wettability based on the surface topography produced by femtosecond laser pulses. In this communication, a Level Set Method (LSM) based model is developed on the commercial multiphysics software platform, COM-SOL, to evaluate the wettability of polished and ultrafast laser-patterned silicon and germanium surfaces. We demonstrate its capacity for simulation of the liquid droplet evolution on various topographies of laser-textured surfaces. The calculations suggest that to achieve more hydrophobic behavior on laser-textured silicon and germanium, more attention should be paid to the height of the relief, and caution should be exercised when varying the period of the relief during femtosecond laser processing