Thomas Bégou

Centrale Marseille

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Thin-Film Optical Elements Based on Chalcogenide Materials

Antoine Bourgade Frédéric Lemarquis Thomas Bégou Julien Lumeau

Thin-film components based on chalcogenide layers will be demonstrated. These component include volume diffractive optical elements based on photo-induced refractive index change or silver photodissolution in As 2 S 3 layers and ultra-uniform bandpass filters based on photosensitive chalcogenide spacers. Theoretical study and design, experimental demonstration and final complete characterization of various optical elements will be presented.

Characterization

Chalcogenide glass

10.1109/icton.2019.8840367

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Broadband antireflection coatings for visible and infrared ranges

International Conference on Space Optics — ICSO 2020 (2019)

Frédéric Lemarquis Thomas Bégou J. Ruscica Daniel Turover Julien Lumeau

Antireflection coatings are among the most common and spread optical coatings that are used in every optical system in order to decrease losses and prevent shadow images. For space applications, they are critical elements which specifications will highly influence the overall optical systems performances. Despite the very wide range of developments that have been carried out over the past thirty years, the production of broadband antireflection coatings for visible and infrared ranges remains a challenge. In this paper, we will present some recent results based on thin film technology for the production of antireflection coatings dedicated to visible, near-IR and mid-IR spectral ranges. We will first present broadband antireflection coatings for [400-1100] nm spectral range We will present two type of coatings, one for normal and one for oblique incidence. Experimental demonstration by plasma assisted reactive magnetron sputtering using a Bühler HELIOS machine will be presented. We will then show antireflection coatings covering the [1.5-15] μm range. Experimental demonstration and limitation will be presented.

Optical coating

Visible spectrum

10.1117/12.2536066

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Versatile Multilayer Metamaterial Nanoparticles with Tailored Optical Constants for Force and Torque Transduction

ACS Nano (2020)

Ying Tang Seungkyu Ha Thomas Bégou Julien Lumeau H. P. Urbach

The ability to apply force and torque directly to micro- and nanoscale particles in optical traps has a wide range of applications. While full control of both force and torque in three dimensions has been realized using top-down fabrication of rod-shaped particles composed of birefringent crystalline materials, widespread usage of such particles is limited as the optical constants of the predominant birefringent materials (quartz SiO2 and rutile TiO2) preclude coverage of the full application space of optical trapping. Here, we show that multilayer metamaterial nanoparticles provide access to a wide range of optical constants that can be specifically tuned for each application. Selecting the material pair Nb2O5/SiO2 from the library of amorphous dielectrics as our metamaterial, we show that its refractive index and birefringence can be designed by adapting the ratio of layer thicknesses. Using a robust top-down fabrication process, we show that uniformly sized, free-floating Nb2O5/SiO2 particles with high birefringence at moderate refractive index are obtained at high yield. Using an optical torque wrench, we show that these particles function as joint force and torque transducers while maintaining excellent stability in aqueous solutions and can be controllably optimized for particular physical characteristics such as maximal torque transfer or rapid response time. We expect that such customizable birefringent metamaterial nanoparticles whose properties surpass those of conventional crystalline particles will provide a means to unleash the full potential of optical trapping applications.

Optical force

10.1021/acsnano.0c04233

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Citations (10)

Comparative study of bandpass filters manufactured by different deposition technologies

Optical Interference Coatings Conference (OIC) 2022 (2019)

Antonin Moreau Thomas Bégou F. Lemarchand Frédéric Lemarquis Karine Mathieu

We perform a comparative study of the performances of thin-film bandpass filters fabricated using plasma assisted reactive magnetron sputtering and electron beam deposition. Design, fabrication and characterization of such filters are presented.

Deposition

Cavity magnetron

Characterization

10.1364/oic.2019.wb.7

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Modeling of optical constants of organosiicon plasma thin films by parameterization of density of states

HAL (Le Centre pour la Communication Scientifique Directe) (2006)

Daniel Franta Lenka Zajı́čková Thomas Bégou A. Bousquet A. Granier

Modeling of optical constants of organosilicon thin films by parameterization of denstity of states

Organosilicon

Constant (computer programming)

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Guides d'ondes pour l'optique intégrée par plasma PECVD

HAL (Le Centre pour la Communication Scientifique Directe) (2008)

Thomas Bégou Akram Soussou K. Makaoui A. Granier Marie‐Paule Besland

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Integrated optics based on plasma processed dielectric materials

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (2008)

Thomas Bégou Bruno Bêche Jean-Pierre Landesman Étienne Gaviot Akram Soussou

A first generation of dielectric rib waveguides has been designed and shaped to support a monomode confinement by using organosilicon materials elaborated by plasma enhanced chemical vapor deposition (PECVD). Optical losses have been measured around 5.5dB.cm^-1 and 11.5dB.cm^-1 for TE₀₀ and TM₀₀ modes, respectively. Then, synthesis of titanium dioxide thin films by PECVD has been investigated to improve optical and propagation properties. The first results on these films exhibit a refractive index around 1.99 at a 633 nm wavelength with a 380 nm optical gap. When an rf bias is applied to the substrate, the refractive index reaches 2.36, from -5V, without significant optical gap variation.

Organosilicon

10.1117/12.793690

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Use of a broadband monitoring system for the determination of the optical constants of a dielectric bilayer

Applied Optics (2018)

S. L. Nadji Michel Lequime Thomas Bégou Cihan Koc Catherine Grèzes-Besset

This paper extends a method previously applied to the determination of the optical constants of a high-index thin film to a dielectric bilayer. This method is based on the time recording of the spectral transmittance of the stack during its deposition with the help of an in situ broadband monitoring system.

10.1364/ao.57.000877

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Citations (5)

Non‐destructive optical analysis of band gap profile, crystalline phase, and grain size for Cu(In,Ga)Se₂ solar cells deposited by 1‐stage, 2‐stage, and 3‐stage co‐evaporation

Progress in Photovoltaics Research and Applications (2013)

Vikash Ranjan Thomas Bégou Scott Little R. W. Collins Sylvain Marsillac

ABSTRACT Cu(In,Ga)Se 2 (CIGS) thin films co‐evaporated by 1‐stage, 2‐stage, and 3‐stage processes have been studied by spectroscopic ellipsometry (SE). The disappearance of a Cu 2‐x Se optical signature, detected by real time SE during multistage CIGS, has enabled precise endpoint control. Band gap energies determined by SE as depth averages show little process variation for fixed [Ga]/([In] + [Ga]) atomic ratio, whereas their broadening parameters decrease with increasing number of stages, identifying successive grain size enhancements. Refined SE analysis has revealed band gap profiling only for 3‐stage CIGS. Solar cells incorporating these absorbers have yielded increased efficiencies in correlation with phase control, grain size, and band gap profiling. Copyright © 2013 John Wiley & Sons, Ltd.

Ellipsometry

10.1002/pip.2350

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Citations (14)

Photonics integrated circuits on plasma-polymer-HMDSO

Thomas Bégou Bruno Bêche Antoine Goulet A. Granier Christophe Cardinaud

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