Laser damage threshold measurements of microstructure-based high reflectors

Douglas S. Hobbs

doi:10.1117/12.804397

30 December 2008 Laser damage threshold measurements of microstructure-based high reflectors

Douglas S. Hobbs

Proceedings Volume 7132, Laser-Induced Damage in Optical Materials: 2008; 71321K (2008) https://doi.org/10.1117/12.804397
Event: Boulder Damage Symposium XL Annual Symposium on Optical Materials for High Power Lasers, 2008, Boulder, Colorado, United States

Abstract

In 2007, the pulsed laser induced damage threshold (LIDT) of anti-reflecting (AR) microstructures built in fused silica and glass was shown to be up to three times greater than the LIDT of single-layer thin-film AR coatings, and at least five times greater than multiple-layer thin-film AR coatings. This result suggested that microstructure-based wavelength selective mirrors might also exhibit high LIDT. Efficient light reflection over a narrow spectral range can be produced by an array of sub-wavelength sized surface relief microstructures built in a waveguide configuration. Such surface structure resonant (SSR) filters typically achieve a reflectivity exceeding 99% over a 1-10nm range about the filter center wavelength, making SSR filters useful as laser high reflectors (HR). SSR laser mirrors consist of microstructures that are first etched in the surface of fused silica and borosilicate glass windows and subsequently coated with a thin layer of a non-absorbing high refractive index dielectric material such as tantalum pent-oxide or zinc sulfide. Results of an initial investigation into the LIDT of single layer SSR laser mirrors operating at 532nm, 1064nm and 1573nm are described along with data from SEM analysis of the microstructures, and spectral reflection measurements. None of the twelve samples tested exhibited damage thresholds above 3 J/cm² when illuminated at the resonant wavelength, indicating that the simple single layer, first order design will need further development to be suitable for high power laser applications. Samples of SSR high reflectors entered in the Thin Film Damage Competition also exhibited low damage thresholds of less than 1 J/cm² for the ZnS coated SSR, and just over 4 J/cm² for the Ta2O5 coated SSR.

Citation Download Citation

Douglas S. Hobbs "Laser damage threshold measurements of microstructure-based high reflectors", Proc. SPIE 7132, Laser-Induced Damage in Optical Materials: 2008, 71321K (30 December 2008); https://doi.org/10.1117/12.804397

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