Experimental investigations on the Higher-order Hermite-Gauss mode interferometry

Thermal noise of the test masses is one of the limiting noise sources in advanced gravitational wave (GW) detectors. It is expected to remain a limiting noise source in future detectors, despite radical changes to the design including cryogenic operations, new materials, and the use of longer laser wavelengths. The so-called "flat beams" such as higher-order Hermite-Gaussian (HG) beams have been studied for thermal noise reduction in GW detectors. They help by better averaging over the random mirror surface fluctuations caused by thermal motions. We have started the experimental investigations on the HG mode interferometry with HG3,3 mode, and we will report on the latest results and progress.