Laser damage of silica optical windows with random antireflective structured surfaces

Christopher R. Wilson; Thomas C. Hutchens; Gopal Sapkota; Jason R. Case; Matthew G. Potter; Lynda E. Busse; Jesse A. Frantz; L. Brandon Shaw; Jas S. Sanghera; Menelaos K. Poutous; Ishwar D. Aggarwal

doi:10.1117/1.OE.57.12.121906

8 November 2018 Laser damage of silica optical windows with random antireflective structured surfaces

Christopher R. Wilson, Thomas C. Hutchens, Gopal Sapkota, Jason R. Case, Matthew G. Potter, Lynda E. Busse, Jesse A. Frantz, L. Brandon Shaw, Jas S. Sanghera, Menelaos K. Poutous, Ishwar D. Aggarwal

Author Affiliations +

Optical Engineering, Vol. 57, Issue 12, 121906 (November 2018). https://doi.org/10.1117/1.OE.57.12.121906

Abstract

High intensity nanosecond laser pulses induce damage on uncoated optics and antireflection (AR) coated optics with thin film boundaries. Structured surfaces with AR performance have shown higher damage resistance than conventional AR coatings. This work explores laser-induced damage threshold (LIDT) of random antireflective surface structures (rARSS), covering interfaces of planar fused silica substrates, using a 7 ± 1 nanosecond duration, single damaging pulse at 1064-nm wavelength. The rARSS treated windows were optimized for AR at 1064 nm, and transmittance of each treated interface was increased by 3.2% per ISO 13697. Incident fluence was controlled near LIDT for both entry and exit sides. Multiple locations were tested for each fluence setting in accordance with ISO 21254 1-on-1 LIDT testing. Double-sided and single-sided rARSS, orientation with both entrance-side and exit-side treatments, were tested to determine effects random structures have in damage induced by field enhancement on the exit side. Results show that rARSS on a single side of an optic have higher resistance to onset of laser damage when located at entry (structured) side. All tests resulting in damage of polished and single-sided rARSS oriented on exit side were ballistic on beam exit facet, showing surface cracks. Results from rARSS located on beam entry side (both single- and double-side treated) showed nonballistic damage and densification of rARSS features from localized melting or reflow, capping the rARSS but still preserving effective-gradient index and rARSS transmission enhancement. This suggests that the localized melting of the rARSS optic surface does not constitute damage optically, or at least not catastrophically within the prebulk damage regime. Therefore, it is possible to foresee the onset of true damage within an optical system via tracking transmission drop, and swap optics out before catastrophic system failure. The drop in transmission acts as an early warning system, making these rARSS optics an invaluable tool in high-energy laser development.

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Christopher R. Wilson, Thomas C. Hutchens, Gopal Sapkota, Jason R. Case, Matthew G. Potter, Lynda E. Busse, Jesse A. Frantz, L. Brandon Shaw, Jas S. Sanghera, Menelaos K. Poutous, and Ishwar D. Aggarwal "Laser damage of silica optical windows with random antireflective structured surfaces," Optical Engineering 57(12), 121906 (8 November 2018). https://doi.org/10.1117/1.OE.57.12.121906

Received: 1 May 2018; Accepted: 11 October 2018; Published: 8 November 2018

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