Laser damage in yttrium orthophosphate

Laser damage experiments on single crystal blades of yttrium orthophosphate were performed. Crystals were grown by slow cooling of a flux containing lead pyrophosphate. Optical absorption is small from about 300 nm to about 3200 nm, approximating the transmission of calcite. A 1.06 micrometer neodymium glass laser with Q-switched pulse duration of 17 ns was used for damage measurements. The laser beam (0.025 cm FWHM) was focussed on the large face of the YPO4 crystals. Visible damage was always observed at front and back crystal surfaces following exposure to pulses averaging 3.6 GW/square centimeter or more. No visible damage was found in YPO4 at power densities less than 2.2 - 2.4 GW/square centimeter. Calcite crystals showed damage at somewhat smaller power densities.