Broad bandwidth high reflection coatings for petawatt class lasers: femtosecond pulse laser damage tests, and measurement of group delay dispersion

John C. Bellum; Trevor B. Winstone; Ella S. Field; Damon E. Kletecka

doi:10.1117/12.2267809

23 February 2017 Broad bandwidth high reflection coatings for petawatt class lasers: femtosecond pulse laser damage tests, and measurement of group delay dispersion

John C. Bellum, Trevor B. Winstone, Ella S. Field, Damon E. Kletecka

Author Affiliations +

Proceedings Volume 10084, High Power Lasers for Fusion Research IV; 100840J (2017) https://doi.org/10.1117/12.2267809
Event: SPIE LASE, 2017, San Francisco, California, United States

Abstract

We designed and produced optical coatings for broad bandwidth high reflection (BBHR) of femtosecond (fs) pulses for high energy petawatt (PW) lasers. These BBHR coatings consist of TiO₂/SiO₂ and/or HfO₂/SiO₂ layer pairs formed by reactive E-beam evaporation with ion-assisted deposition in Sandia’s Large Optics Coating Facility. Specifications for the HR band and center wavelength of the coatings are for 45° angle of incidence (AOI), P polarization (Ppol), with use of the coatings at different AOIs and in humid or dry/vacuum environments providing corresponding different HR center wavelengths and spectral widths. These coatings must provide high laserinduced damage threshold (LIDT) to handle the PW fluences, and also low group delay dispersion (GDD) to reflect fs pulses without distortion of their temporal profiles. We present results of LIDT and GDD measurements on these coatings. The LIDT tests are at 45° or 65° AOI, Ppol in a dry environment with 100 fs laser pulses of 800 nm line center for BBHR coatings whose HR band line centers are near 800 nm. A GDD measurement for one of the BBHR coatings whose design HR center wavelength is near 900 nm shows reasonably low and smoothly varying GDD over the HR band. Our investigations include BBHR coatings designed for 45° AOI, Ppol with HR bands centered at 800 nm in dry or vacuum environments, and featuring three options: all TiO₂/SiO₂ layer pairs; all HfO₂/SiO₂ layer pairs; and TiO₂/SiO₂ inner layer pairs with 5 outer HfO₂/SiO₂ layer pairs. LIDT tests of these coatings with 100 fs, 800 nm line center pulses in their use environment show that replacing a few outer TiO₂ layers of TiO₂/SiO₂ BBHR coatings with HfO₂ leads to ~ 80% higher LIDT with only minor loss of HR bandwidth.

Conference Presentation

Citation Download Citation

John C. Bellum, Trevor B. Winstone, Ella S. Field, and Damon E. Kletecka "Broad bandwidth high reflection coatings for petawatt class lasers: femtosecond pulse laser damage tests, and measurement of group delay dispersion", Proc. SPIE 10084, High Power Lasers for Fusion Research IV, 100840J (23 February 2017); https://doi.org/10.1117/12.2267809

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