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Functional Damage Thresholds of Hafnia/Silica Coating Designs for the NIF Laser

Conference ·
OSTI ID:807787
 [1]; ; ; ; ; ;
  1. Laboratory for Laser Energetics, University of Rochester, Rochester, NY
Studies into the functional damage thresholds of hafnia/silica thin-film coatings for the NIF laser have been conducted on two different-sized substrates: 50-mm-diam test substrates and full-sized (412 x 412-mm) NIF mirror substrates. For both studies, the optics were raster scanned by Q-switched Nd:YAG lasers emitting 1064-nm light with 10-ns pulse lengths. The coatings tested were primarily high reflectors, although polarizing beam splitter and antireflective thin films were tested on the small substrates. Tests were performed to find the functional damage threshold: the minimum fluence at which a damaged optic degrades the performance of the NIF laser, or, experimentally, the minimum fluence at which a damaged site begins to grow. Thus, the concern is with finding not only the fluence that caused a pit (for example) but also the fluence at which that pit begins to grow with subsequent laser shots. After a site begins a growth phase, the growth rate is measured as a function of fluence. This provides some information for predicting the optic lifetime for given operating limits of the laser.
Research Organization:
Laboratory for Laser Energetics (US)
Sponsoring Organization:
(US)
DOE Contract Number:
FC03-92SF19460
OSTI ID:
807787
Report Number(s):
DOE/SF-19460-473; 1344; 2000-119
Country of Publication:
United States
Language:
English