Speaker
Description
In order to reduce thermal noise, KAGRA operates at cryogenic temperatures with crystalline test-masses. The non-uniform birefringence of these test-masses distorts the beam circulating in the detector and can limit the detector’s sensitivity. These issues could be even more severe for future generation of detectors with larger crystalline test-masses.
In this talk, we will report our activities towards the demonstration of low-loss compensation of non-uniform birefringence: From the demonstration of 1D birefringence compensation to spatial- and time-varying birefringence compensation and low-loss compensation. This so-called BIGFOOT project is now one of the KAGRA R&D projects. Furthermore, the techniques developed during this project also permit the development of new birefringence characterization techniques.