The effect of time on optical coating mechanical loss and implications for LIGO-India
We report on the persistence of mechanical loss with time of ion beam sputtered dielectric coatings made from alternating layers of Ta_2O_5 and SiO_2 deposited onto fused silica substrates. From this, we predict the coating thermal noise in gravitational wave interferometers, after the coated optics have been stored for years. We measured the modal mechanical quality factor, Q, of two coated fused silica samples in 2015. These samples also had their modal Q's measured in 2002. We conclude that storing the coated silica disks for 13 years does not change their mechanical loss and thus the storage of Advanced LIGO gravitational wave detector optics until their future installation in India will not degrade their achievable thermal noise.
© 2016 IOP Publishing Ltd. Received 23 March 2016, revised 9 May 2016; Accepted for publication 23 May 2016; Published 23 June 2016. This research was funded by the US National Science Foundation under grant number PHY-1453252. This paper has been assigned LIGO Document Number LIGO-P1600076.