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Optimizing a cleaning process for multilayer-dielectric- (MLD) diffraction gratings

Conference · · Proceedings of SPIE - The International Society for Optical Engineering
DOI:https://doi.org/10.1117/12.751750· OSTI ID:922683
 [1];  [2];  [2];  [2]
  1. Univ. of Rochester, NY (United States); Laboratory for Laser Energetics, University of Rochester, Rochester, NY
  2. Univ. of Rochester, NY (United States)
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An essential component for the OMEGA EP short-pulse petawatt laser system is the grating compressor chamber (GCC). This large (12,375 ft3) vacuum chamber contains critical optics where laser-pulse compression is performed at the output of the system on two 40-cm-sq-aperture, IR (1054-nm) laser beams. Critical to this compression, within the GCC, are four sets of tiled multilayer-dielectric- (MLD) diffraction gratings that provide the capability for producing 2.6-kJ output IR energy per beam at 10 ps. The primary requirements for these large-aperture (43-cm × 47-cm) gratings are diffraction efficiencies greater than 95%, peak-to-valley wavefront quality of less than λ/10 waves, and laser-induced-damage thresholds greater than 2.7 J/cm2 at 10-ps measured beam normal. Degradation of the grating laser-damage threshold due to adsorption of contaminants from the manufacturing process must be prevented to maintain system performance. In this paper we discuss an optimized cleaning process to achieve the OMEGA EP requirements. The fabrication of MLD gratings involves processes that utilize a wide variety of both organic materials (photoresist processes) and inorganic materials (metals and metal oxides) that can affect the final cleaning process. Finally, a number of these materials have significant optical absorbance; therefore, incomplete cleaning of these residues may result in the MLD gratings experiencing laser damage.

Research Organization:
Univ. of Rochester, NY (United States)
Sponsoring Organization:
USDOE National Nuclear Security Administration (NNSA), Office of Inertial Confinement Fusion
DOE Contract Number:
FC52-92SF19460
OSTI ID:
922683
Report Number(s):
DOE/SF--19460-802; 2007-58; 1773
Journal Information:
Proceedings of SPIE - The International Society for Optical Engineering, Journal Name: Proceedings of SPIE - The International Society for Optical Engineering Vol. 6720; ISSN 0277-786X
Publisher:
SPIE
Country of Publication:
United States
Language:
English

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Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
CLEANING
DIFFRACTION GRATINGS
LASERS
MLD diffraction gratings
OMEGA FACILITY
OPTICS
cleaning
damage threshold