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

Conference · Thu Dec 20 00:00:00 EST 2007 · Proceedings of SPIE - The International Society for Optical Engineering

DOI:https://doi.org/10.1117/12.751750· OSTI ID:922683

Ashe, B. ^[1]; Giacofei, C. ^[1]; Myhre, G. ^[1]; Schmid, A. W. ^[1]

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1. Univ. of Rochester, NY (United States)

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; TRN: US0801134
• Journal Information: Proceedings of SPIE - The International Society for Optical Engineering, Vol. 6720; Conference: Laser-Induced Damage in Optical Materials, Boulder, CO (United States), 24-26 Sep 2007; ISSN 0277-786X
• Publisher: SPIE
• Country of Publication: United States
• Language: English

Related Subjects

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