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Proceedings Paper

Long-duration CW laser testing of optical windows with random antireflective surface structures on both interfaces: preliminary results
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Paper Abstract

High power laser optical systems can suffer damage from uncoated optics due to undesirable Fresnel reflections. With high power lasers, traditional anti-reflection (AR) thin-film coated optics are susceptible to localized field enhancement regions, due to multiple boundaries, and experience laser induced damage on both entry and exit interfaces. Sub-wavelength random anti-reflective surface structures (rARSS) have been shown to have a higher laserinduced damage threshold than traditional AR coatings. Previously published work detailed nanosecond-pulsed laserinduced damage on rARSS on both single surface and dual surface of optical quality, planar, fused silica substrates at 1064 nm. This study details laser fatigue testing of double-sided rARSS samples via continuous wave, 2 kW ytterbiumfiber- laser irradiation (1075 nm). Laser output was focused to increase incident intensity at the initial interface. The laser spot was focused to ~ 60-μm-diameter (1/e2) yielding a maximum power density of 70.7 MW/cm2. Laser power, test duration, and testing grid were controlled externally via LabVIEW software. Damage testing sites maintained the same laser power density (70.7 MW/cm2) and varied by irradiation time, incrementally from one minute up to one hour. It was determined that double-sided rARSS substrates have a higher damage threshold than thin-film AR coatings, showing no damage of the AR structures at power densities up to 70.7 MW/cm2 and laser irradiation times up to one hour at each interrogation site, while thin-film samples have been reported to fail with power density as low as 2 MW/cm2.

Paper Details

Date Published: 8 May 2018
PDF: 6 pages
Proc. SPIE 10627, Advanced Optics for Defense Applications: UV through LWIR III, 106270H (8 May 2018); doi: 10.1117/12.2317882
Show Author Affiliations
Christopher R. Wilson, The Univ of North Carolina at Charlotte (United States)
Thomas C. Hutchens, The Univ of North Carolina at Charlotte (United States)
Lynda E. Busse, Naval Research Lab. (United States)
Jesse A. Frantz, Naval Research Lab. (United States)
L. Brandon Shaw, Naval Research Lab. (United States)
Jas S. Sanghera, Naval Research Lab. (United States)
Ishwar D. Aggarwal, KeyW Corp. (United States)

Published in SPIE Proceedings Vol. 10627:
Advanced Optics for Defense Applications: UV through LWIR III
Jay N. Vizgaitis; Bjørn F. Andresen; Peter L. Marasco; Jasbinder S. Sanghera; Miguel P. Snyder, Editor(s)

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