Thermo-optic noise in coated mirrors for high-precision optical measurements

Thermoelastic dissipation in inhomogeneous media: loss measurements and displacement noise in coated test masses for interferometric gravitational wave detectors

The displacement noise in the test mass mirrors of interferometric gravitational wave detectors is proportional to their elastic dissipation at the observation frequencies. In this paper, we analyze one fundamental source of dissipation in thin coatings, thermoelastic damping associated with the dissimilar thermal and elastic properties of the film and the substrate. We obtain expressions for the thermoelastic dissipation factor necessary to interpret resonant loss measurements, and for the spectral density of displacement noise imposed on a Gaussian beam reflected from the face of a coated ma…

Brownian Thermal Noise in Multilayer Coated Mirrors

We analyze the Brownian thermal noise of a multi-layer dielectric coating, used in high-precision optical measurements including interferometric gravitational-wave detectors. We assume the coating material to be isotropic, and therefore study thermal noises arising from shear and bulk losses of the coating materials. We show that coating noise arises not only from layer thickness fluctuations, but also from fluctuations of the interface between the coating and substrate, driven by internal fluctuating stresses of the coating. In addition, the non-zero photoeleastic coefficients of the thin fil…

降低多材料镀膜有限基底热弹性损耗的策略

Strategies to reduce the thermoelastic loss of multimaterial coated finite substrates

本文提出解析模型分析多材料镀膜有限基底的热弹性损耗，发现降低温度、减薄镀层、增加界面及优化首层材料可减少损耗，助力低噪声引力波探测器设计。

The implications of Mexican-hat mirrors: calculations of thermoelastic noise and interferometer sensitivity to perturbation for the Mexican-hat-mirror proposal for advanced LIGO

Thermoelastic noise will be the most significant noise source in advanced-LIGO interferometers with sapphire test masses. The standard plan for advanced-LIGO has optimized the optics, within the framework of conventional mirrors, to reduce thermoelastic noise. Recently, we and our collaborators have proposed going beyond the bounds of traditional optics to increase the effective beam spot size and thus lower thermoelastic noise. One particular proposal for mirror shapes (``Mexican-hat mirrors'') yields the class of ``mesa'' beams. In this paper, we outline a general procedure for analyzing lig…

Excess Mechanical Loss Associated with Dielectric Mirror Coatings on Test Masses in Interferometric Gravitational Wave Detectors

Interferometric gravitational wave detectors use mirrors whose substrates are formed from materials of low intrinsic mechanical dissipation. The two most likely choices for the test masses in future advanced detectors are fused silica or sapphire. These test masses must be coated to form mirrors, highly reflecting at 1064nm. We have measured the excess mechanical losses associated with adding dielectric coatings to substrates of fused silica and calculate the effect of the excess loss on the thermal noise in an advanced interferometer.

Thermoelastic-damping noise from sapphire mirrors in a fundamental-noise-limited interferometer

We report the first high-precision interferometer using large sapphire mirrors, and we present the first direct, broadband measurements of the fundamental thermal noise in these mirrors. Our results agree well with the thermoelastic-damping noise predictions of Braginsky, et al. [Phys. Lett. A 264, 1(1999)] and Cerdonio, et al.[Phys. Rev. D 63, 082003 (2001)], which have been used to predict the astrophysical reach of advanced interferometric gravitational wave detectors.