Experimental Demonstration of Next-Generation Wavefront Control for LIGO and Beyond

The Laser Interferometer Gravitational-Wave Observatory (LIGO) first detected gravitational waves in 2015, pioneering a new way to observe the universe through geometric spacetime fluctuations. Future upgrades seek to obtain over a megawatt of circulating laser power within its arm cavities, but thermal distortions of the test masses arising from the absorption of incident laser power are a major limiting factor. The FROnt Surface Type Irradiator (FROSTI) is designed to augment LIGO's existing Thermal Compensation System in mitigating these aberrations by applying a corrective higher-order heating profile to the mirror surface—reducing the residual wavefront distortions as well as mitigating problematic higher-mode co-resonances of the arm cavities. FROSTI will have a direct impact on LIGO's ability to see into earlier times of the universe and further enable tests of gravity, cosmology, and dense nuclear matter. We present the first experimental demonstration of a FROSTI prototype on a real 40-kg LIGO test mass, confirming that this technology can provide proper actuation to the mirror, exhibits low outgassing levels compatible with the LIGO ultra-high vacuum environment, and avoids introducing significant additional noise into the system output.