Optical Detection of Melting Point Depression For Silver Nanoparticles Via In Situ Real Time Spectroscopic Ellipsometry

Silver nanoparticle films were deposited by sputtering at room temperature and were annealed while monitoring by real time spectroscopic ellipsometry (SE). The nanoparticle dielectric functions (0.75 eV-6.5 eV) obtained by SE were modeled using Lorentz and generalized oscillators for the nanoparticle plasmon polariton (NPP) and interband transitions, respectively. The nanoparticle melting point could be identified from variations in the oscillator parameters during annealing, and this identification was further confirmed after cooling through significant, irreversible changes in these parameters relative to the as-deposited film. The variation in melting point with physical thickness, and thus average nanoparticle diameter, as measured by SE enables calculation of the surface energy density

All dielectric broadband mirror for Fabry-Perot interferometer

International audienceWe present our first results on Fabry-Perot plates manufacturing with a broadband dielectric mirror on the front side and an antireflective coating on the rear face. Physical thicknesses of both coatings are optimized to reduce stress deformations

Influence of regular dance practice on the postural stability during quiet standing in healthy women

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Chalcogenide-based Ultra-uniform Narrow Bandpass Filters

Summer 2020 SVC Bulletin, 76-84 (2020)International audienc

Semi-automated method for the determination of the all-optical monitoring strategy of complex thin-film filters

International audienceOne of the critical steps in the fabrication of complex optical interference filters is the precise control of the thickness of the layers during the fabrication process. However, the definition of the optimal optical monitoring strategy remains a challenge as it relies on user experience and there is no reliable automatic determination of this strategy. Here, we propose a semi-automated method that allows the determination of the optimal strategy. It is based on the combination of trinary mappings to select spectral regions that are compatible with optical monitoring and the use of the reflected phase error at a single wavelength versus optical monitoring wavelength. We show how this procedure can be used for the determination of either a single optical monitoring wavelength or a multi-wavelength procedure of a complex filter and confirm these theoretical results with an experimental demonstration

In-situ interferometric monitoring of optical coatings

International audienceWe present a new method for the in situ measurement of the amplitude and phase of the reflection coefficient of a plane substrate installed in a mechanical holder rotating at high speed (120 turns per minute) during the deposition of an optical thin-film stack. Our method is based on digital holography and uses a self-referenced scheme to cancel the effects of the severe constraints generated by the vibrational and thermal environment of the deposition machine

Marcatili's extended approach: comparison to semi-vectorial methods applied to pedestal waveguide design

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X-ray reflectometry study of diamond-like carbon films prepared by plasma enhanced chemical vapor deposition in a low pressure inductively coupled plasma

International audienceIn this work we probe the structural properties of amorphous hydrogenated carbon thin films prepared by plasma-enhanced chemical vapor deposition in a low pressure inductively coupled plasma using X-ray reflectometry in order to study the effect of varying the ion energy on the density of these films. The ion energy is varied by varying the RF power used to bias the substrate. It is shown that a very low ion energy is already sufficient to obtain a dense diamond-like carbon (DLC) film, in contrast with other deposition techniques where much higher ion energies are required to obtain a dense DLC film. The results of this study are corroborated by Raman spectroscopy and ellipsometry measurements. The X-ray reflectometry data analysis is detailed in order to highlight some methodological problems encountered during the data fitting which could lead to an incorrect interpretation of the measured curves

Influence of Ion Bombardment and Annealing on the Structural and Optical Properties of TiOx Thin Films Deposited in Inductively Coupled TTIP/O-2 Plasma

International audienceTiO2 films were deposited in a low-pressure inductively coupled rf plasma in O-2/titanium tetraisopropoxide (TTIP). First, depositions were realized at floating potential using nitrogen as bubbling gas. The structural and optical properties of the films were studied, before and after annealing at 450 degrees C under air. As expected, as-deposited films are amorphous, with a columnar structure. A post-annealing under flowing air allows obtaining partially crystallized films in anatase phase. Secondly, films were deposited using nitrogen and oxygen as bubbling gas. In both cases, TiO2-like films exhibit very similar structure and optical properties. Finally, the effect of biasing the substrate was investigated. An improvement of film proper-ties has been found for a bias voltage of -15 V at T < 100 degrees C: deposited TiO2 film is dense (3.7) with a high refractive index (n = 2.32 at 634 nm) and partially crystallized in rutile phase