Michel Lequime
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View article: All-dielectric metasurface polarization scrambler for imaging applications
All-dielectric metasurface polarization scrambler for imaging applications Open
The partial polarization of the earth's radiation can be the source of radiometric errors for space instruments with polarization-sensitive components. It is therefore necessary to have a device capable of depolarizing the light before it …
View article: Impact of localized defects in light scattered by optical components: measurement and analysis
Impact of localized defects in light scattered by optical components: measurement and analysis Open
Defects and contaminants can be a critical source of performance loss. This paper presents and demonstrates the capabilities of a new SPatially and Angularly Resolved Scatterometry Equipment (SPARSE) designed to measure spatially resolved …
View article: Optical losses as a function of beam position on the mirrors in a 285-m suspended Fabry-Perot cavity
Optical losses as a function of beam position on the mirrors in a 285-m suspended Fabry-Perot cavity Open
Reducing optical losses is crucial for reducing quantum noise in gravitational-wave detectors. In fact, with equal input power, a lower level of round-trip losses in the arm cavities allows more power to be stored. Moreover, losses are the…
View article: Comparison of arm cavity optical losses for the two wavelengths of the Einstein Telescope gravitational wave detector
Comparison of arm cavity optical losses for the two wavelengths of the Einstein Telescope gravitational wave detector Open
A new generation of gravitational wave detectors is currently being designed with the likely use of a different laser wavelength compared to current instruments. The estimation of the optical losses for this new wavelength is particularly …
View article: Thermal detuning of a bichromatic narrow linewidth optical cavity
Thermal detuning of a bichromatic narrow linewidth optical cavity Open
In the Advanced Virgo+ interferometric gravitational-wave detector, the length control of the Fabry-Pérot cavities in the arms and of the detuned filter cavity, used for generating frequency-dependent squeezing, uses an auxiliary green bea…
View article: Interferometric quantification and identification of back-reflected and back-scattered light from a system of two optical components
Interferometric quantification and identification of back-reflected and back-scattered light from a system of two optical components Open
In this work, we recorded the retro-reflected and back-scattered light from a system of two components i.e, a single side AR coated SiO2 window and a mirror placed at tilt angle of 10◦ in the transmission of the window. Retro-re…
View article: Spatially resolved scattering metrology to quantify losses induced by contamination and defects
Spatially resolved scattering metrology to quantify losses induced by contamination and defects Open
In less than 20 years, extraordinary progress has been made on the design and manufacturing of planar optical components, especially in terms of minimizing light scattering (a few 10−6 of the incident flux). This progress is clo…
View article: SPARSE: a high performance scatterometer with imaging ability
SPARSE: a high performance scatterometer with imaging ability Open
View article: Low-coherence interferometric measurement of the spatial frequency dependence of the light field backscattered by optical interfaces
Low-coherence interferometric measurement of the spatial frequency dependence of the light field backscattered by optical interfaces Open
In this paper, we show how the combined use of low-coherence interferometry, balanced detection, and data processing comparable to that used in Fourier transform spectrometry allows us to characterize with ultimate resolutions (sub-parts p…
View article: Low coherence interferometric detection of the spectral dependence of the retro-reflection coefficient of an anti-reflective coated interface
Low coherence interferometric detection of the spectral dependence of the retro-reflection coefficient of an anti-reflective coated interface Open
The measurement of very low reflection coefficients of anti-reflective coated interfaces has become a key issue for the realization of precision instruments such as the giant interferometers used for the detection of gravitational waves. W…
View article: Low-coherence interferometric measurement of the spectral dependence of the light field backscattered by optical interfaces
Low-coherence interferometric measurement of the spectral dependence of the light field backscattered by optical interfaces Open
In this paper, we show how the combined use of low coherence interferometry, balanced detection and data processing comparable to that used in Fourier transform spectrometry allows us to characterize with ultimate resolutions (sub-ppm in l…
View article: Instantaneous measurement of surface roughness spectra using white-light scattering projected on a spectrometer
Instantaneous measurement of surface roughness spectra using white-light scattering projected on a spectrometer Open
Following on from previous studies on motionless scatterometers based on the use of white light, we propose a new, to the best of our knowledge, experiment of white-light scattering that should overtake the previous ones in most situations…
View article: Low coherence interferometric detection of the spectral dependence of the retro-reflection coefficient of an anti-reflective coated interface
Low coherence interferometric detection of the spectral dependence of the retro-reflection coefficient of an anti-reflective coated interface Open
The measurement of very low reflection coefficients of anti-reflective coated interfaces has become a key issue for the realization of precision instruments such as the giant interferometers used for the detection of gravitational waves. W…
View article: Provable Phase Retrieval with Mirror Descent
Provable Phase Retrieval with Mirror Descent Open
In this paper, we consider the problem of phase retrieval, which consists of recovering an $n$-dimensional real vector from the magnitude of its $m$ linear measurements. We propose a mirror descent (or Bregman gradient descent) algorithm b…
View article: Reconstruction de Phase Garantie par Descente Miroir
Reconstruction de Phase Garantie par Descente Miroir Open
National audience
View article: Analysis of the multilayer organization of a sunflower leaf during dehydration with terahertz time-domain spectroscopy
Analysis of the multilayer organization of a sunflower leaf during dehydration with terahertz time-domain spectroscopy Open
We apply reverse engineering techniques (RET) to analyze the dehydration process of a sunflower leaf with terahertz time-domain spectroscopy. The multilayer structure of the leaf is extracted with accuracy during the entire process. Time v…
View article: Immediate and one-point roughness measurements using spectrally shaped light
Immediate and one-point roughness measurements using spectrally shaped light Open
Capitalizing on a previous theoretical paper, we propose a novel approach, to our knowledge, that is different from the usual scattering measurements, one that is free of any mechanical movement or scanning. Scattering is measured along a …
View article: Micro-cavity optimization for ultra-sensitive all-dielectric optical sensors
Micro-cavity optimization for ultra-sensitive all-dielectric optical sensors Open
We present an analytical method for the optimization of luminescent micro-cavities to create a substrate that is extremely sensitive to contamination. Giant optical enhancement can thus be controlled arbitrarily and simultaneously at vario…
View article: Detection of Ultralow Light Power Back-Reflected or Back-Scattered by Optical Components Using Balanced Low-Coherence Interferometry
Detection of Ultralow Light Power Back-Reflected or Back-Scattered by Optical Components Using Balanced Low-Coherence Interferometry Open
International audience
View article: Towards a metasurface adapted to hyperspectral imaging applications: from subwavelength design to definition of optical properties
Towards a metasurface adapted to hyperspectral imaging applications: from subwavelength design to definition of optical properties Open
We numerically demonstrate the capability of a single metasurface to simultaneously separate and focus spectral features in accordance with the specifications of a pushbroom hyperspectral imager. This is achieved through the dispersion eng…
View article: Optimization of micro-cavities for huge enhancement patterns in free-space and modal space
Optimization of micro-cavities for huge enhancement patterns in free-space and modal space Open
Optical sources within micro-cavities have been extensively studied for years [1]–[3]. It is today well known that over-coating these cavities with multilayer optics allows to modify their emission patterns in free space in the surrounding…
View article: Design of multilayer optical thin-films based on light scattering properties and using deep neural networks
Design of multilayer optical thin-films based on light scattering properties and using deep neural networks Open
Despite limiting the performance of multilayer optical thin-films, light scattering properties are not as yet controllable by current design methods. These methods usually consider only specular properties: transmittance and reflectance. A…
View article: Trapped light scattering within optical coatings: a multilayer roughness-coupling process
Trapped light scattering within optical coatings: a multilayer roughness-coupling process Open
Despite numerous works devoted to light scattering in multilayer optics, trapped scattering has not been considered until now. This consists in a roughness-coupling process at each interface of the multilayer, giving rise to electromagneti…
View article: A breakthrough instrument for wide-range wavelength and angle resolved light scattering measurements of high performances optical coatings
A breakthrough instrument for wide-range wavelength and angle resolved light scattering measurements of high performances optical coatings Open
Due to the diversity and complexity of optical functions they address, optical coatings are widely used in space optics but the level of both their specifications and performances is now so high that the characterization of their optical p…
View article: Coherent detection of the light backscattered by an optical surface
Coherent detection of the light backscattered by an optical surface Open
We measured very low light power backscattered by optical surfaces using low coherence interferometry. The backscattered light can indeed be a critical noise source for interferometric gravitational wave detectors such as LISA, the laser i…
View article: In-situ interferometric monitoring of optical coatings
In-situ interferometric monitoring of optical coatings Open
We 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 optic…
View article: Wide-range wavelength and angle resolved light scattering measurement setup
Wide-range wavelength and angle resolved light scattering measurement setup Open
We present a new version of a light scattering measurement setup, using a high-power supercontinuum laser source, two volume hologram filters, and two low-noise scientific grade cameras. This configuration enables spectral and angle resolv…
View article: International round-robin experiment for angle-resolved light scattering measurement
International round-robin experiment for angle-resolved light scattering measurement Open
An international round-robin experiment has been conducted to test procedures and methods for the measurement of angle-resolved light scattering. ASTM E2387-05 has been used as the main guide, while the experience gained should also contri…
View article: Analysis and control of light scattered by optical components for space applications
Analysis and control of light scattered by optical components for space applications Open
Space applications require more and more demanding optical functions. This evolution led to the development of new generation of optical components with extreme performances in terms of scattering level, roughness, localized defects, spect…
View article: Breakthrough spectrophotometric instrument for the ultra-fine characterization of the spectral transmittance of thin-film optical filters
Breakthrough spectrophotometric instrument for the ultra-fine characterization of the spectral transmittance of thin-film optical filters Open
In this paper, we provide a detailed description of the main features of the upgraded version of a spectrophotometric apparatus developed by our team since 2014 [ Opt. Express23, 26863 (2015)]), and whose improved performance allows the ch…