Reducing Thermal Noise in Future Gravitational Wave Detectors by employing Khalili Etalons

TL;DR

This paper demonstrates that Khalili etalons can significantly reduce thermal noise in gravitational wave detectors, offering a hardware-efficient alternative to Khalili cavities with comparable noise reduction benefits.

Contribution

The study introduces Khalili etalons as a simpler, effective means to lower thermal noise in gravitational wave detectors, optimizing coating layer distribution.

Findings

Khalili etalons reduce thermal noise effectively.

Optimal coating layer distribution identified.

Comparison shows advantages over conventional mirrors.

Abstract

Reduction of thermal noise in dielectric mirror coatings is a key issue for the sensitivity improvement in second and third generation interferometric gravitational wave detectors. Replacing an end mirror of the interferometer by an anti-resonant cavity (a so-called Khalili cavity) has been proposed to realize the reduction of the overall thermal noise level. In this article we show that the use of a Khalili etalon, which requires less hardware than a Khalili cavity, yields still a significant reduction of thermal noise. We identify the optimum distribution of coating layers on the front and rear surfaces of the etalon and compare the total noise budget with a conventional mirror. In addition we briefly discuss advantages and disadvantages of the Khalili etalon compared with the Khalili cavity in terms of technical aspects, such as interferometric length control and thermal lensing.