Low stress ion-assisted coatings on fused silica substrates for large aperture laser pulse compression gratings

Douglas J. Smith; Mike McCullough; Claire Smith; Takuya Mikami; Takahisa Jitsuno

doi:10.1117/12.817336

30 December 2008 Low stress ion-assisted coatings on fused silica substrates for large aperture laser pulse compression gratings

Douglas J. Smith, Mike McCullough, Claire Smith, Takuya Mikami, Takahisa Jitsuno

Author Affiliations +

Proceedings Volume 7132, Laser-Induced Damage in Optical Materials: 2008; 71320E (2008) https://doi.org/10.1117/12.817336
Event: Boulder Damage Symposium XL Annual Symposium on Optical Materials for High Power Lasers, 2008, Boulder, Colorado, United States

Abstract

Large aperture laser pulse compressor designs use several diffraction gratings in series and sometimes tiled together to compress an amplified 1 to 10 ns pulse to 0.1 to 10 ps. The wavefront of the compressed pulse must be well controlled to allow focusing to a small spot on a target. Traditionally, multilayer dielectric gratings (MLDG) have been fabricated onto high thermal expansion substrates such as BK7 glass to prevent crazing and excessive bending due to tensile coating stress when operated in high vacuum. However, the high CTE of the BK7 can cause wavefront distortion and changes in the period of the grating. This work uses ion-assisted deposition of HfO₂/SiO₂ films to increase the compressive stress in MLD layers to allow use of silica substrates in the compressor vacuum environment. Stress, coating uniformity, and damage results are reported. The process was scaled to full size (91cm × 42cm) MLD gratings for use in the Osaka University LFEX laser system. Diffracted wavefront results from the full scale gratings is presented.

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Douglas J. Smith, Mike McCullough, Claire Smith, Takuya Mikami, and Takahisa Jitsuno "Low stress ion-assisted coatings on fused silica substrates for large aperture laser pulse compression gratings", Proc. SPIE 7132, Laser-Induced Damage in Optical Materials: 2008, 71320E (30 December 2008); https://doi.org/10.1117/12.817336

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