Correlated evolution of structure and mechanical loss of a sputtered silica film

Energy dissipation in amorphous coatings severely affects high-precision optical and quantum transducers. In order to isolate the source of coating loss, we performed an extensive study of Raman scattering and mechanical loss of a thermally-treated sputtered silica coating. Our results show that loss is correlated with the population of three-membered rings of Si-O$_4$ tetrahedral units, and support the evidence that thermal treatment reduces the density of metastable states separated by a characteristic energy of about 0.5 eV, in favour of an increase of the states separated by smaller activation energies. Finally, we conclude that three-fold rings are involved in the relaxation mechanisms only if they belong to more complex chain-like structures of 10 to 100 tetrahedra.Comment: 5 pages, 3 figure

Étude et réalisation d'empilements multicouches sur des optiques asphériques de grandes dimensions pour des applications en lithographie extrême U.V.

La réalisation d optiques de grandes dimensions est un élément clé à la réussite de la lithographie Extrême-Ultraviolet à 13,5 nm. Leur intégration dans les appareils de production doit permettre d acheminer un flux lumineux intense de la source jusqu au wafer et ainsi d augmenter la productivité. Nous avons étudié et développé des systèmes multicouches à base de molybdène et silicium. Leurs structures ont été étudiées par réflectométrie des rayons X et leurs performances mesurées à 13,5 nm sous rayonnement synchrotron. Les résultats ont révélé une réflectivité à 13,5 nm limitée principalement à cause de la faible qualité des interfaces due à l inter-diffusion des 2 matériaux. Nous avons aussi porté une attention particulière au traitement de substrats asphériques de grandes dimensions. Nous avons notamment utilisé des techniques de masquage permettant de contrôler les épaisseurs déposées sur des diamètres de près de 500 mm et malgré des flèches proches de 100 mmThe development of large optics is a crucial point for the success of the EUV lithography at 13.5 nm. The integration of large collectors into steppers allows a gain in the collecting beam and thus improves the throughput. We have studied and developed reflecting molybdenum and silicon multilayers at 13.5 nm. Structures were analyzed using grazing incidence reflectometry and performances were measured under Synchrotron radiation at operating wavelength. The diffusion observed between the two materials at each interface severely reduces the total reflectivity at 13.5 nm. We have also studied coatings on large aspherical substrates. To control the gradient profile coatings on large concave collectors ( clear aperture of 500 mm and sag about 100 mm), we have used with success the masking techniqueLYON1-BU.Sciences (692662101) / SudocSudocFranceF

Point defects in IBS coating for very low loss mirrors

International audienceHigh reflective coatings are used in many physics experiments. Despite the high quality of the opticalcoating, the performances of the mirrors is altered by the scattered light induced by micrometers sizedefects in the coating layers. The topic of this paper is the study of the point-like scatterers present in thespecific coating of the mirrors used in state of the art, high sensitivity optical experiments. We studied thebehavior of the materials according to different thicknesses, and how the defects change after annealing.To our knowledge, this is a first insight into the formation of such defects for different materials andthickness and how this is reduced when samples are annealed

Dichroic and anti-reflective coatings for astronomical instrumentation

International audienceDue to the increase of astronomical projects and of their instruments, the request of large optics with higher optical performances does not stop growing. An important step in the manufacture of these optics is the deposition of high-precision optical coatings. To answer to this request we developed coatings working at different angles of incidence and spectral ranges on large surface: - anti-reflective coatings for large lenses with strong curvatures, - dichroic coatings with sharp transition for large optics. Main results will be presented on the basis of several examples of realization. © (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

High precision metrology for large bandpass filters

International audienceHigh precision measurements of the filters bandpass used on wide-field imagers mounted on large telescopes is critical for type Ia supernovae studies. A dedicated spectrophotometric bench is used to re-measure the now decommissioned ugriz filters used for the SNLS on CFHT-MegaCam. A full characterization of the optical response with respect to the location on the surface and the angle of incidence was performed for each filter. Strong variation over the filter surface is observed. The impact of the actual response on the observation is evaluated and we demonstrate an improvement with respect to the previous published results (SNLS1 and 2). © (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

Large and extremely low loss: the unique challenges of gravitational wave mirrors

International audienceThis paper describes the making of large mirrors for laser interferometer gravitational wave detectors. These optics, working in the near infrared, are among the best optics ever created and played a crucial role in the first direct detection of gravitational waves from black holes or neutron star fusions

MICADO SCAO: to be or not to be... in MAIT

International audienceMICADO SCAO: to be or not to be... in MAI

The population of merging compact binaries inferred using gravitational waves through GWTC-3

v2: minor edits, most to Table 1 and caption; v3: rerun with public data; Data release: https://zenodo.org/record/5655785; v4: update Fig 14We report on the population properties of 76 compact binary mergers detected with gravitational waves below a false alarm rate of 1 per year through GWTC-3. The catalog contains three classes of binary mergers: BBH, BNS, and NSBH mergers. We infer the BNS merger rate to be between 10 $\rm{Gpc^{-3} yr^{-1}}$ and 1700 $\rm{Gpc^{-3} yr^{-1}}$ and the NSBH merger rate to be between 7.8 $\rm{Gpc^{-3}\, yr^{-1}}$ and 140 $\rm{Gpc^{-3} yr^{-1}}$ , assuming a constant rate density versus comoving volume and taking the union of 90% credible intervals for methods used in this work. Accounting for the BBH merger rate to evolve with redshift, we find the BBH merger rate to be between 17.9 $\rm{Gpc^{-3}\, yr^{-1}}$ and 44 $\rm{Gpc^{-3}\, yr^{-1}}$ at a fiducial redshift (z=0.2). We obtain a broad neutron star mass distribution extending from $1.2^{+0.1}_{-0.2} M_\odot$ to $2.0^{+0.3}_{-0.3} M_\odot$. We can confidently identify a rapid decrease in merger rate versus component mass between neutron star-like masses and black-hole-like masses, but there is no evidence that the merger rate increases again before 10 $M_\odot$. We also find the BBH mass distribution has localized over- and under-densities relative to a power law distribution. While we continue to find the mass distribution of a binary's more massive component strongly decreases as a function of primary mass, we observe no evidence of a strongly suppressed merger rate above $\sim 60 M_\odot$. The rate of BBH mergers is observed to increase with redshift at a rate proportional to $(1+z)^{\kappa}$ with $\kappa = 2.9^{+1.7}_{-1.8}$ for $z\lesssim 1$. Observed black hole spins are small, with half of spin magnitudes below $\chi_i \simeq 0.25$. We observe evidence of negative aligned spins in the population, and an increase in spin magnitude for systems with more unequal mass ratio