Speaker
Description
In order to mitigate thermal noise, the gravitational wave detector KAGRA operates at cryogenic temperatures. Due to its poor thermal and mechanical coefficients, fused silica cannot be used at these temperatures. For this reason, KAGRA’s test masses are made with sapphire.
Sapphire test masses have inhomogeneous birefringent properties. This property is suspected to distort the error signals used for the alignment of the Fabry-Perot cavities of the detector. The distortion of error signals could limit KAGRA’s sensitivity.
In this work, we built a tabletop experiment where we used an inhomogeneous birefringent plate in front of a Fabry-Perot cavity to simulate a birefringent input test mass. We studied the birefringence coupling to the alignment control of the cavity with this experiment and Finesse 3.0 simulations. We will use this experiment to study mitigation and compensation of the birefringence-induced misalignment in optical cavity.