Analysis of coating defects in cavity mirrors for the IR Upgrade FEL

Michelle D. Shinn; Christopher Gould

doi:10.1117/12.585399

21 February 2005 Analysis of coating defects in cavity mirrors for the IR Upgrade FEL

Michelle D. Shinn, Christopher Gould

Author Affiliations +

Proceedings Volume 5647, Laser-Induced Damage in Optical Materials: 2004; (2005) https://doi.org/10.1117/12.585399
Event: Boulder Damage Symposium XXXVI, 2004, Boulder, Colorado, United States

Abstract

Noncontact optical profilometry was used to characterize the surface flaws on cavity mirrors used in the IR Upgrade FEL at the Tomas Jefferson National Accelerator Facility (JLab). The FEL exposes the cavity mirrors, which have multilayer dielectric coatings, to a unique pulse format. To date, when lasing at 6 mirons at a PRF of 37.4 MHz, the circulating cw power is in excess of 100 kW, the peak cw irradiance exceeds 30 kW/cm², and the peak irradiance of each pulse is of order 1 GW/cm². While state-of-the-art, these coatings are far from defect-free, yet have survived those operating conditions without damage after hours of use. The use of noncontact profilometry and the latest software allows us to characterize the size, depth, and distribution of defects in the area covered by the beam footprint in a way that is far more useful than a scratch-dig value. These data provide benchmarks for what defects can be tolerated for lasers having similar irradiances.

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Michelle D. Shinn and Christopher Gould "Analysis of coating defects in cavity mirrors for the IR Upgrade FEL", Proc. SPIE 5647, Laser-Induced Damage in Optical Materials: 2004, (21 February 2005); https://doi.org/10.1117/12.585399

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