As an important optical element, beam sampling grating (BSG) is used in the terminal of inertial confinement fusion (ICF) drivers. It can provide a very slight sampling beam for the precision diagnosing of laser energy and wavefront distortion. However, in practice, its non-uniform diffraction efficiency seriously influences the accurate signal of sampling beam, and finally affects diagnostic ability. BSG is usually fabricated by holographic ion beam etched (HIBE) process. In this paper, a mechanical polishing processing technology was used to improve uniformity of the diffraction efficiency of BSG after HIBE. In the processing, cerium oxide (CeO₂) was used to polish the local areas of grating where exhibit higher diffraction efficiency with the purpose of changing the depth of grating profile, and then they have similar efficiency with the surrounding areas. By iteration of the above process, BSG finally achieve the improved uniformity of diffraction efficiency over the area of a 430 x 430 mm². The RMS of diffraction efficiency of BSG after mechanical polishing shows great reduction down to 4.8% as compared with that of the as-polished RMS of 21%. The effects of this processing on laser damage was characterized by the measuring the LIDT for the laser radiations of 355nm.

Date Published: 12 January 2012
PDF: 7 pages
Proc. SPIE 8206, Pacific Rim Laser Damage 2011: Optical Materials for High Power Lasers, 820613 (12 January 2012); doi: 10.1117/12.910341

Published in SPIE Proceedings Vol. 8206:
Pacific Rim Laser Damage 2011: Optical Materials for High Power Lasers
Jianda Shao, Editor(s)