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Title: Evaluation of cleaning methods for multilayer diffraction gratings

Abstract

Multilayer dielectric (MLD) diffraction gratings are a crucial component for the OMEGA EP short-pulse, highenergy laser system. The MLD gratings must have both high-optical-diffraction efficiency and high laser-damage threshold to be suitable for use within the OMEGA EP Laser System. Considerable effort has been directed toward optimizing the process parameters required to fabricate gratings that can withstand the 2.6-kJ output energy delivered by each beam. In this paper, we discuss a number of conventional semiconductor chemical cleaning processes that have been investigated for grating cleaning, and present evidence of their effectiveness in the critical cleaning of MLD gratings fabricated at LLE. Diffraction efficiency and damage-threshold data were correlated with both scanning electron microscopy (SEM) and time-of-flight secondary ion-mass spectrometry (ToF-SIMS) to determine the best combination of cleaning process and chemistry. Finally, we found that using these cleaning processes we were able to exceed both the LLE diffraction efficiency (specification >97%) and laser-damage specifications (specification >2.7 J/cm 2).

Authors:
 [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1]
  1. Univ. of Rochester, NY (United States)
Publication Date:
Research Org.:
Univ. of Rochester, NY (United States). Lab. for Laser Energetics
Sponsoring Org.:
USDOE
OSTI Identifier:
900757
Report Number(s):
DOE/SF-19460-729
Journal ID: ‎ISSN 0277-786X; 2006-157; 1691; TRN: US200720%%162
DOE Contract Number:
FC52-92SF19460
Resource Type:
Conference
Resource Relation:
Journal Name: Proceedings of SPIE - The International Society for Optical Engineering; Journal Volume: 6403; Conference: Laser-Induced Damage in Optical Materials, Boulder, CO (United States), 25-27 Sep 2006
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CHEMISTRY; CLEANING; DIELECTRIC MATERIALS; DIFFRACTION; DIFFRACTION GRATINGS; EFFICIENCY; EVALUATION; LASERS; SCANNING ELECTRON MICROSCOPY; SPECIFICATIONS; SPECTROSCOPY; Diffraction gratings; Multilayers; Diffraction; Laser induced damage; Lasers; Chemicals; Chemistry; Scanning electron microscopy; Semiconductors; Spectroscopy

Citation Formats

Ashe, B., Marshall, K. L., Giacofei, C., Rigatti, A. L., Kessler, T. J., Schmid, A. W., Oliver, J. B., Keck, J., and Kozlov, A.. Evaluation of cleaning methods for multilayer diffraction gratings. United States: N. p., 2007. Web. doi:10.1117/12.694884.
Ashe, B., Marshall, K. L., Giacofei, C., Rigatti, A. L., Kessler, T. J., Schmid, A. W., Oliver, J. B., Keck, J., & Kozlov, A.. Evaluation of cleaning methods for multilayer diffraction gratings. United States. doi:10.1117/12.694884.
Ashe, B., Marshall, K. L., Giacofei, C., Rigatti, A. L., Kessler, T. J., Schmid, A. W., Oliver, J. B., Keck, J., and Kozlov, A.. Mon . "Evaluation of cleaning methods for multilayer diffraction gratings". United States. doi:10.1117/12.694884.
@article{osti_900757,
title = {Evaluation of cleaning methods for multilayer diffraction gratings},
author = {Ashe, B. and Marshall, K. L. and Giacofei, C. and Rigatti, A. L. and Kessler, T. J. and Schmid, A. W. and Oliver, J. B. and Keck, J. and Kozlov, A.},
abstractNote = {Multilayer dielectric (MLD) diffraction gratings are a crucial component for the OMEGA EP short-pulse, highenergy laser system. The MLD gratings must have both high-optical-diffraction efficiency and high laser-damage threshold to be suitable for use within the OMEGA EP Laser System. Considerable effort has been directed toward optimizing the process parameters required to fabricate gratings that can withstand the 2.6-kJ output energy delivered by each beam. In this paper, we discuss a number of conventional semiconductor chemical cleaning processes that have been investigated for grating cleaning, and present evidence of their effectiveness in the critical cleaning of MLD gratings fabricated at LLE. Diffraction efficiency and damage-threshold data were correlated with both scanning electron microscopy (SEM) and time-of-flight secondary ion-mass spectrometry (ToF-SIMS) to determine the best combination of cleaning process and chemistry. Finally, we found that using these cleaning processes we were able to exceed both the LLE diffraction efficiency (specification >97%) and laser-damage specifications (specification >2.7 J/cm2).},
doi = {10.1117/12.694884},
journal = {Proceedings of SPIE - The International Society for Optical Engineering},
number = ,
volume = 6403,
place = {United States},
year = {Mon Jan 15 00:00:00 EST 2007},
month = {Mon Jan 15 00:00:00 EST 2007}
}

Conference:
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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 ft 3) 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,more » and laser-induced-damage thresholds greater than 2.7 J/cm 2 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.« less
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