Improving the performance of high-laser-damage-threshold, multilayer dielectric pulse-compression gratings through low-temperature chemical cleaning

Abstract

A low-temperature chemical cleaning approach has been developed to improve the performance of multilayer dielectric pulse-compressor gratings for use in the OMEGA EP laser system. X-ray photoelectron spectroscopy results guided the selection of targeted cleaning steps to strip specific families of manufacturing residues without damaging the grating's fragile 3D profile. Grating coupons that were cleaned using the optimized method consistently met OMEGA EP requirements on diffraction efficiency and 1054 nm laser-damage resistance at 10 ps. The disappearance of laser-conditioning effects for the highest-damage-threshold samples suggests a transition from a contamination-driven laser-damage mechanism to defect-driven damage for well-cleaned components.

Mechanisms of picosecond laser-induced damage in common multilayer dielectric coatings

“…The damage-test laser system used in this study has been described in detail elsewhere 12,16 . The laser is operating at 1053 nm, and the pulse duration is adjustable between 600 fs and 100 ps.…”

Near-ultraviolet absorption annealing in hafnium oxide thin films subjected to continuous-wave laser radiation

“…Laser-damage testing of cw laser exposed and unexposed sample areas was performed in a 1-on-1 regime, using 351nm, 0.9-ns pulses of a Nd:YLF diode-pumped laser 6 and 1053-nm, 600-fs, best-compression pulses from a laser using the standard chirped pulse amplification scheme. 7 Damage testing using 0.9-ns pulses was conducted in an ambient environment and testing with 600-fs pulses was performed in a 10 −7 -Torr vacuum to avoid self-focusing in air. The laser beam spot size (1∕e 2 ) on the sample was 400 and 270 μm for 0.9-ns and 600-fs beams, respectively.…”

Plasma-ion-assisted coatings for 15 femtosecond laser systems

“…The primary testing for fs-coating performance was performed by Lidaris (formerly VULRC, Vilnius University) with an 800 nm laser and a 59 fs pulse. Damage testing was also performed at LLE by systems at 1053 nm with 1 ns, 10 ps, and 0.6 ps pulse durations, with testing at the nanosecond-and picosecond-pulse durations in accordance with the protocols described by Howard et al [36] and Papernov [37]. In all cases, coating designs were adjusted from a nominal 910 nm center wavelength to center the coating performance at the wavelength being tested.…”