Substrate-transferred GaAs/AlGaAs crystalline coatings for gravitational-wave detectors

Cole, Garrett D.; Ballmer, S. W.; Billingsley, G.; Cataño-Lopez, S. B.; Fejer, M. M.; Fritschel, P.; Gretarsson, A. M.; Harry, G. M.; Kedar, Dhruv; Legero, Thomas; Makarem, C.; Penn, S.; Reitze, D. H.; Steinlechner, J.; Sterr, U.; Tanioka, S.; Truong, Gar-Wing; Ye, Jun; Yu, Jialiang

doi:10.1063/5.0140663

Cited by 7 publications

(2 citation statements)

References 47 publications

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“…In recent times, crystalline coatings are emerging as a promising alternative for use in GW detectors [13]. These coatings are characterized by a mechanical loss angle, which is one order of magnitude smaller than that of amorphous HI materials.…”

Section: Introductionmentioning

confidence: 99%

Reduction of mechanical losses in ion-beam sputtered tantalum oxide thin films via partial crystallization

Favaro,

Milotti,

Alonso Diaz Riega

et al. 2024

Class. Quantum Grav.

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This study explores the impact of crystalline fraction on the mechanical losses of amorphous tantalum oxide (tantala, Ta2O5) thin films intended for gravitational wave detectors. We use ion beam sputtering (IBS) technique to prepare a series of samples, which are then subjected to controlled thermal annealing to achieve varying degrees of crystallized fraction. The microscopic structure of the annealed samples is characterized by combining different analytical techniques. Our investigation reveals that the amorphous films comprise randomly distributed crystalline grains, whose density and average size depends on the duration of thermal treatment. To assess mechanical losses of the coatings, a Gentle Nodal Suspension (GeNS) system is applied. Remarkably, a substantial reduction of approximately 20% in the coating’s mechanical loss angle with respect to annealed amorphous coatings is observed for samples exhibiting a crystalline fraction of around 5%. This improvement may lead to the definition of alternative thermal treatments to improve the mechanical performances of coatings for gravitational wave detectors or other highly sensitive optical experiments. However the reduction in mechanical losses comes at the expense of an increase in optical scattering. The possibility of reducing the optical losses to the level required by gravitational interferometers by modifying the grain size distribution via appropriate annealing treatments is discussed.

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Section: Introductionmentioning

confidence: 99%

Reduction of mechanical losses in ion-beam sputtered tantalum oxide thin films via partial crystallization

Favaro,

Milotti,

Alonso Diaz Riega

et al. 2024

Class. Quantum Grav.

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show abstract

“…To date, AlGaAs/GaAs, a crystalline coating, has the best CTN characteristics [4], well under the required noise levels, and promising optical losses. Crystalline coatings however may need to address other challenges, such as birefringent noise or increased scattering and absorption defect density [21,22]. In addition, the largest crystalline coating that can currently be fabricated is 10 cm in radius.…”

Section: Introductionmentioning

confidence: 99%

Clipping losses from a piecewise coated mirror

Kontos

Loglia

2023

Class. Quantum Grav.

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The properties of optical coatings play an important role in precision experiments. Gravitational-wave detectors not only require the highest quality coatings but also ones withrelatively large diameters. Coatings made with amorphous material can be scaled up easily but for now exhibit relatively high thermal noise characteristics. Crystalline coatings show great promise in terms of their thermal noise properties but cannot easily scale up to the needed sizes. In this paper we explore the possibility of a piecewise coating that includes both amorphous and crystalline material. Specifically, we estimate the scattering losses of such a piecewise coating as a function of the mismatch in the interface between the two coatings. The calculation should be taken as a lower limit to the total losses, as other surface imperfections will play an important role in the final result, but are not considered here. Finally, we present a measurement of the scattering losses from a piecewise coating, to showcase the challenges of realizing such a design.

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Mid-infrared supermirrors with finesse exceeding 400 000

Truong,

Perner,

Bailey

et al. 2023

Nat Commun

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For trace gas sensing and precision spectroscopy, optical cavities incorporating low-loss mirrors are indispensable for path length and optical intensity enhancement. Optical interference coatings in the visible and near-infrared (NIR) spectral regions have achieved total optical losses below 2 parts per million (ppm), enabling a cavity finesse in excess of 1 million. However, such advancements have been lacking in the mid-infrared (MIR), despite substantial scientific interest. Here, we demonstrate a significant breakthrough in high-performance MIR mirrors, reporting substrate-transferred single-crystal interference coatings capable of cavity finesse values from 200 000 to 400 000 near 4.5 µm, with excess optical losses (scatter and absorption) below 5 ppm. In a first proof-of-concept demonstration, we achieve the lowest noise-equivalent absorption in a linear cavity ring-down spectrometer normalized by cavity length. This substantial improvement in performance will unlock a rich variety of MIR applications for atmospheric transport and environmental sciences, detection of fugitive emissions, process gas monitoring, breath-gas analysis, and verification of biogenic fuels and plastics.

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Substrate-transferred GaAs/AlGaAs crystalline coatings for gravitational-wave detectors

Cited by 7 publications

References 47 publications

Reduction of mechanical losses in ion-beam sputtered tantalum oxide thin films via partial crystallization

Reduction of mechanical losses in ion-beam sputtered tantalum oxide thin films via partial crystallization

Clipping losses from a piecewise coated mirror

Mid-infrared supermirrors with finesse exceeding 400 000

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