Improving gravitational-wave detector sensitivity with cryogenic test mass cooling
Abstract: Interferometric gravitational wave detectors use the reflective surfaces of seismically isolated test masses as inertial position references to measure the stretching of space due to passing gravitational waves. Thermal noise of the coatings, substrates, and fiber suspensions, which distorts the reflected wave fronts and causes displacement noise in the interferometer readout, is a limiting factor in current detectors, and needs to be significantly lowered for any future improvements in sensitivity. Cryogenic cooling reduces the amount of thermal energy in the mirrors, resulting in lower thermal noise, but comes with severe design constraints to keep the mirrors inertial and requires new substrate and coating materials. I will discuss the difficulties of cryogenic detector upgrades and present coating research and prototyping efforts using table-top optical experiments.