*Chalisa Gier1, Stuart Reid1, Marwa Ben-Yaala1, Svetoslava Angelova1, Ross Birney1,2, Paul Hill1, Jim Hough3, Iain Martin3, Peter Murray3, Sheila Rowan3, Simon Tait3, Gavin Wallace1, Callum Wiseman1
1University of Strathclyde, Glasgow, United Kingdom; 2University of the West of Scotland, Paisley, United Kingdom; 3University of Glasgow, Glasgow, United Kingdom
Ion beam deposition (IBD) is a method generally used for the fabrication of Bragg reflectors with extremely low levels of optical loss. Gravitational wave detector mirrors are one example which requires high-reflectivity, through use of multilayer dielectric coatings, that require sub-ppm absorption over large area. Although, the Brownian thermal noise of typical coating materials, due to the mechanical dissipation, remains too high to allow future gravitational wave detectors to reach their quantum-limited sensitivities. Therefore, the University of Strathclyde have developed a new IBD process to extend the available parameter range during manufacture, along with providing additional potential benefits. This technique utilized electron cyclotron resonance (ECR) plasma generation, alongside an extraction geometry which yields a cleaner and more precisely controlled extraction for generating an energetic ion beam for sputtering. This technique has been used to fabricate the lowest optical absorption amorphous silicon in the world; k = 1.2 x 10-5 at 1550 nm – a factor of 100 lower than standard RF-IBD. This talk will describe a new scaled-up deposition system being commissioned, with 6 independent ECR sources, enabling unique opportunities for developing novel alloys such as ultra-stable glasses. Relevance for other applications requiring ultra-low optical loss and high laser-induced damage threshold are discussed, along with the results obtained by manipulating the deposition parameters and the effect it has on the coatings’ optical properties.