What's it about?

The use of high-power continuous wave (CW) lasers in the emerging directed energy (DE) market has put greater emphasis on the quality of optical coatings. These coatings (both high reflectance and anti-reflection) require high damage thresholds for use at irradiances up to and greater than 1 MW/cm2. The challenge in the coating process is to minimize the number of coating defects that can contribute to absorption and eventual coating failure.

The industry lacks standardized testing to detect possible defects at the required irradiances for DE optics. To aid in the development of coating designs and production techniques for DE related optics, we have constructed a high-irradiance Ytterbium fiber laser-based scanning metrology system to detect absorbing defects in DE optical coatings. Defects are detected by their localized thermal heating creating a hot-spot. The goal of this work is to continually improve the coating, increase the laser damage threshold, and contribute to a standard for the testing and validation of directed energy optical coatings.