Test mass materials for a new generation of gravitational wave detectors

To obtain improved sensitivities in future generations of interferometric gravitational wave detectors, beyond those proposed as upgrades of current detectors, will require different approaches in different portions of the gravitational wave frequency band. However the use of silicon as an interferometer test mass substrate, along with all-reflective interferometer topologies, could prove to be a design enabling sensitivity improvements at both high and low frequencies. In this paper the thermo-mechanical properties of silicon are discussed and the potential benefits from using silicon as a mirror substrate material in future gravitational wave detectors are outlined.