Laser smoothing of sub-micron grooves in hydroxyl-rich fused silica

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Nano- to micrometer-sized surface defects on UV-grade fused silica surfaces are known to be effectively smoothed through the use of high-temperature localized CO{sub 2} laser heating, thereby enhancing optical properties. However, the details of the mass transport and the effect of hydroxyl content on the laser smoothing of defective silica at submicron length scales is still not completely understood. In this study, we examine the morphological evolution of sub-micron, dry-etched periodic surface structures on type II and type III SiO{sub 2} substrates under 10.6 {micro}m CO{sub 2} laser irradiation using atomic force microscopy (AFM). In-situ thermal imaging was used to ... continued below

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PDF-file: 27 pages; size: 0.9 Mbytes

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Shen, N; Matthews, M J; Fair, J E; Britten, J A; Nguyen, H T; Cooke, D et al. October 30, 2009.

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Nano- to micrometer-sized surface defects on UV-grade fused silica surfaces are known to be effectively smoothed through the use of high-temperature localized CO{sub 2} laser heating, thereby enhancing optical properties. However, the details of the mass transport and the effect of hydroxyl content on the laser smoothing of defective silica at submicron length scales is still not completely understood. In this study, we examine the morphological evolution of sub-micron, dry-etched periodic surface structures on type II and type III SiO{sub 2} substrates under 10.6 {micro}m CO{sub 2} laser irradiation using atomic force microscopy (AFM). In-situ thermal imaging was used to map the transient temperature field across the heated region, allowing assessment of the T-dependent mass transport mechanisms under different laser-heating conditions. Computational fluid dynamics simulations correlated well with experimental results, and showed that for large effective capillary numbers (N{sub c} > 2), surface diffusion is negligible and smoothing is dictated by capillary action, despite the relatively small spatial scales studied here. Extracted viscosity values over 1700-2000K were higher than the predicted bulk values, but were consistent with the surface depletion of OH groups, which was confirmed using confocal Raman microscopy.

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PDF-file: 27 pages; size: 0.9 Mbytes

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  • Journal Name: Applied Surface Science, vol. 256, no. 12, April 1, 2010, pp. 4031-4037; Journal Volume: 256; Journal Issue: 12

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  • Report No.: LLNL-JRNL-420282
  • Grant Number: W-7405-ENG-48
  • Office of Scientific & Technical Information Report Number: 974861
  • Archival Resource Key: ark:/67531/metadc925966

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Office of Scientific & Technical Information Technical Reports

Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

Office of Scientific and Technical Information (OSTI) is the Department of Energy (DOE) office that collects, preserves, and disseminates DOE-sponsored research and development (R&D) results that are the outcomes of R&D projects or other funded activities at DOE labs and facilities nationwide and grantees at universities and other institutions.

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  • October 30, 2009

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  • Nov. 13, 2016, 7:26 p.m.

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  • Dec. 8, 2016, 8:27 p.m.

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Shen, N; Matthews, M J; Fair, J E; Britten, J A; Nguyen, H T; Cooke, D et al. Laser smoothing of sub-micron grooves in hydroxyl-rich fused silica, article, October 30, 2009; Livermore, California. (digital.library.unt.edu/ark:/67531/metadc925966/: accessed October 18, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.