Combined advanced finishing and UV-laser conditioning for producing UV-damage-resistant fused-silica optics

Abstract

Laser-induced damage initiation on fused silica optics can limit the lifetime of the components when used in high power UV laser environments. For example in inertial confinement fusion research applications, the optics can be exposed to temporal laser pulses of about 3 nsec with average fluences of 8 J/cm2 and peak fluences between 12 and 15 J/cm2. During the past year, we have focused on optimizing the damage performance at a wavelength of 355-nm (3(omega) ), 3-nsec pulse length, for optics in this category by examining a variety of finishing technologies with a challenge to improve the laser damage initiation density by at least two orders of magnitude. In this paper, we describe recent advances in improving the 3(omega) damage initiation performance of laboratory-scale zirconium oxide and cerium oxide conventionally finished fused silica optics via application of processes incorporating magnetorheological finishing (MRF), wet chemical etching, and UV laser conditioning. Details of the advanced finishing procedures are described and comparisons are made between the procedures based upon large area 3(omega) damage performance, polishing layer contamination, and optical subsurface damage.