Reactively sputtered optical coatings for use at 1064 NM

Optical coatings of TiO 2 , In 1 . 9 Sn 0 . 1 O 3 (ITO), Ta 2 O 5 , Nb 2 O 5 , a-Si:H and SiO 2 have been prepared by reactive sputtering for use with lasers operating near 1064 nm. Damage thresholds of 7-10 J/cm 2 for TiO 2 and5-6 J/cm 2 for transparent-conductive ITO were measured at Lawrence Livermore Laboratory for λ/2 coatings on fused silica irradiated with 1 nsec laser pulses. Sputtered Ta 2 O 5 , Nb 2 O 5 and a-Si:H also appear to be promising high-index coating materials, but have not yet been damage tested. The reactive sputtering process is shown to allow precise control of coating crystalline phase and grain size. For TiO 2 both optical properties and damage threshold have been related to these materials properties, and glassy coatings are shown to be optimal.