Experimental Investigations Toward Improving Thermal Noise in Amorphous Coatings for Advanced LIGO

Coating thermal noise is one of the fundamental limits to the sensitivity of the current and future gravitational wave detectors in their most sensitive region between 40 and 100 Hz. Presently, silica and titania doped tantala are used as the low and high refractive index material respectively in the multilayer, amorphous dielectric coatings used in Advanced LIGO. Our goal is to reduce coating thermal noise, opening the road to a similar improvement in the gravitational wave detector sensitivities at all frequencies. In this talk we present the status of current experimental efforts aimed at reducing the thermal noise of amorphous coatings, in the framework of the stable glass hypothesis. In particular, we discuss the effect of deposition at elevated substrate temperature on the mechanical properties of pure tantala thin films.