Experimental measurements of mechanical dissipation associated with dielectric coatings formed using SiO2, Ta2O5 and Al2O3

Previous studies have quantified the mechanical dissipation associated with dielectric thin films formed from alternating layers of ion-beam-sputtered SiO2 and Ta2O5 and concluded that such dissipation could lead to potentially significant levels of thermally induced displacement noise in proposed advanced gravitational wave detectors. We report here, for the first time, measurements of the mechanical dissipation of coatings formed from alternating layers of Al2O3 and Ta2O5 , and SiO2 and Al2O3 , respectively, when applied to fused silica substrates. In addition, we report our measurements of the elastic properties of Al2O3 /Ta2O5 and SiO2 /Ta2O5 coatings, as the film elastic properties can significantly influence expected levels of coating thermal noise. In summary, our analysis suggests that SiO2 /Ta2O5 coatings currently present the best option for future detectors from a thermal noise standpoint.