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Proceedings Paper

Low stress ion-assisted coatings on fused silica substrates for large aperture laser pulse compression gratings
Author(s): Douglas J. Smith; Mike McCullough; Claire Smith; Takuya Mikami; Takahisa Jitsuno
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Paper 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.

Paper Details

Date Published: 30 December 2008
PDF: 7 pages
Proc. SPIE 7132, Laser-Induced Damage in Optical Materials: 2008, 71320E (30 December 2008); doi: 10.1117/12.817336
Show Author Affiliations
Douglas J. Smith, Plymouth Grating Lab. (United States)
Mike McCullough, Plymouth Grating Lab. (United States)
Claire Smith, Plymouth Grating Lab. (United States)
Takuya Mikami, Okamoto Optics Works (Japan)
Takahisa Jitsuno, Osaka Univ. (Japan)

Published in SPIE Proceedings Vol. 7132:
Laser-Induced Damage in Optical Materials: 2008
Gregory J. Exarhos; Detlev Ristau; M. J. Soileau; Christopher J. Stolz, Editor(s)

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