High-Reflection Coatings for Gravitational-Wave Detectors:<i>State of The Art and Future Developments</i>

Amato, A.; Cagnoli, G.; Canepa, M.; Coillet, Elodie; Degallaix, J.; Dolique, V.; Forest, Danièle; Granata, M.; Martinez, V.; Michel, C.; Pinard, L.; Sassolas, B.; Teillon, Julien

doi:10.1088/1742-6596/957/1/012006

Cited by 37 publications

(64 citation statements)

References 12 publications

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“…This finding has possible interesting implications regarding a deeper comprehension of the mechanical behavior of these coatings for GWD purposes. Indeed, the finding regarding the Urbach tails parallels the well-known (yet still not fully understood) doping-induced reduction of internal friction observed in these films [7]. It has been shown that there is a correlation between mechanical losses and the disordered structure of this coatings [16,25].…”

Section: Resultssupporting

confidence: 73%

“…Regarding Ti:Ta 2 O 5 coating refractive index values, made at LMA, exploiting several Ti concentration were early presented in [12]. In that study Ti:Ta 2 O 5 coatings were deposited using various coating machines and variety of deposition methods, which provide films with different mechanical and optical properties [7]. In particular, the deposition conditions adopted to create the coatings analyzed in [12] were not the same used to deposit the materials currently used in GWD.…”

Section: Coatingmentioning

confidence: 99%

“…Such ground-based interferometers use large, massive suspended mirrors as gravitational field probes, where the mirror high-reflection coatings are made of stacked oxide materials having alternate refractive index. In facts, mirrors used in current interferometers are ion beam sputtered (IBS) coatings made of several doublets of low-and high-index of refraction amorphous oxides [7]. The mirrors in operation have been produced at Laboratoire des Matériaux Avancés (LMA, Lyon, France) using an IBS custom-made apparatus (Grand Coater, GC), able to deposit very uniform coatings over very large surfaces, with diameter of some tens of cm.…”

Section: Introductionmentioning

confidence: 99%

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Optical properties of high-quality oxide coating materials used in gravitational-wave advanced detectors

et al. 2019

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High-reflection interference mirrors for current gravitational wave detectors (aLIGO, Advanced Virgo, KAGRA) are made of high-quality oxide multi-layers deposited by ion beam sputtering (IBS) at the Laboratoire des Matériaux Avancés (LMA). For this task, LMA uses a large IBS custom-made machine (the grand coater GC) able to deposit very uniform coatings over very large surfaces, with diameter of some tens of cm. We report for the first time about the optical characterization by spectroscopic ellipsometry of oxide coatings deposited by the GC under strictly the same conditions used for the production of interference mirrors. We have investigated oxide materials like silica (SiO 2 ), tantala (Ta 2 O 5 ) and titania-doped tantala (Ti:Ta 2 O 5 ), providing for each material a broad-band (190-1700 nm) accurate determination of the complex index of refraction, with particular attention to wavelengths used in interferometers. Particular focus has been dedicated to the influence of Tidoping on tantala coating. The doping induces a red-shift of the optical gap and an increase of the NIR refractive index. Furthermore, doping induces a decrease of the so-called Urbach energy, consistent with the well-known reduction of the internal friction in these kind of systems.

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Section: Resultssupporting

confidence: 73%

Section: Coatingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Optical properties of high-quality oxide coating materials used in gravitational-wave advanced detectors

et al. 2019

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“…To increase the refractive index contrast by replacing the current co-sputtered Ta 2 O 5 -TiO 2 layers with higher-index materials, we tested Ta 2 O 5 -TiO 2 coatings with different Ti/Ta mixing ratios [31], Nb 2 O 5 layers and co-sputtered TiO 2 -Nb 2 O 5 coatings. Also, following preliminary results from the LIGO Collaboration, we tried Ta 2 O 5 -ZrO 2 coatings treated at higher annealing temperatures.…”

Section: Alternative Oxides and Dopingmentioning

confidence: 99%

“…Usually, such coatings are deposited by chemical vapor deposition (CVD), suffering from high optical absorption (k ∼ 1 − 5 · 10 −5 ) due to hydrogen contamination [34]; moreover, their thickness uniformity still remains to be tested against the stringent requirements of GW detectors. Thus we chose to develop our own IBS SiN x coatings and test their loss versus the annealing temperature [31]. The latest results are shown in Figs.…”

Section: Silicon Nitridementioning

confidence: 99%

Progress in the measurement and reduction of thermal noise in optical coatings for gravitational-wave detectors

et al. 2020

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Coating thermal noise is a fundamental limit for precision experiments based on optical and quantum transducers. In this review, after a brief overview of the techniques for coating thermal noise measurements, we present the latest world-wide research activity on low-noise coatings, with a focus on the results obtained at the Laboratoire des Matériaux Avancés. We report new updated values for the Ta 2 O 5 , Ta 2 O 5 -TiO 2 and SiO 2 coatings of the Advanced LIGO, Advanced Virgo and KAGRA detectors, and new results from sputtered Nb 2 O 5 , TiO 2 -Nb 2 O 5 , Ta 2 O 5 -ZrO 2 , MgF 2 , AlF 3 and silicon nitride coatings. Amorphous silicon, crystalline coatings, high-temperature deposition, multi-material coatings and composite layers are also briefly discussed, together with the latest developments of structural analyses and models. The issue of coating thermal noiseThe Laboratoire des Matériaux Avancés (LMA, now a division of the newly created Institut de Physique des 2 Infinis de Lyon) has provided the current high-reflection (HR) and anti-reflective (AR) coatings of the most critical optics of Advanced LIGO [1], Advanced Virgo [2] and KAGRA [3]. In these gravitational-wave (GW) interferometers, large and massive suspended mirrors (typically with ∅ = 35 cm, t = 20 cm, m = 40 kg) form the km-long resonant Fabry-Perot cavities where the astrophysical signals are embedded in the laser beam phase. Their HR coatings are Bragg reflectors of alternate layers of ion-beam-sputtered (IBS) low-and high-refractive index materials, which feature outstanding optical properties [4]. At the same time, these amorphous coatings are the source of coating thermal noise (CTN), which is a severe limitation to the detector sensitivity [1,2].In GW interferometers, thermal noise arises from fluctuations of the mirror surface under the random motion of particles in coatings and substrates [5,6]. Its power spectral density is determined by the amount of internal friction within the mirror materials, via the fluctuationdissipation theorem [7]: the higher the elastic energy loss, the higher the thermal noise level. As the coating loss is usually several orders of magnitude larger than that of the substrate [8,9], CTN is the dominant source of noise in the mirrors.More generally, CTN is a fundamental limit for precision experiments based on optical and quantum transducers, such as opto-mechanical resonators [10], frequency standards [11] and quantum computers [12]. In the last two decades, a considerable research effort has been committed to the measurement and the reduction of CTN.

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Research and Development for Third-Generation Gravitational Wave Detectors

Ward

Slagmolen

Aso

2021

Handbook of Gravitational Wave Astronomy

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High-Reflection Coatings for Gravitational-Wave Detectors:State of The Art and Future Developments

Cited by 37 publications

References 12 publications

Optical properties of high-quality oxide coating materials used in gravitational-wave advanced detectors

Optical properties of high-quality oxide coating materials used in gravitational-wave advanced detectors

Progress in the measurement and reduction of thermal noise in optical coatings for gravitational-wave detectors

Research and Development for Third-Generation Gravitational Wave Detectors

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