Speaker
Description
Crystalline coatings have been shown to have significantly lower Brownian noise compared to amorphous materials, because oftheir lower mechanical loss. This property offers significant advantages in high-precision metrology and investigations on fundamental physics. In gravitational-wave detection, AlGaAs/GaAs multilayer coatings are considered for next-generation detectors with projected reductions in thermal coating noise by a factor of $\sim ~$3 at room temperature compared to current amorphous oxide coatings.
However, as a semiconductor material which has an anisotropic structure and free charge carriers, the crystalline coatings will introduce some noises which are absent in the amorphous coatings.
In this talk, we will present an overview of the noise sources relevant to crystalline materials in gravitational detectors. We will start from the known Brownian noise and Coating thermo-optic noises, which are common to both crystalline and amorphous materials. Then we will focus on crystalline coatings and discuss birefringence and carrier driven noises, such as Generation-recombination noise, photo-optical noise, and thermally driven charge carrier noise. We will discuss the noises physical mechanism, frequency dependence, and scaling with beam size and laser intensity, which could provide some insight to the noise budget of crystalline coatings for gravitational wave detectors.