A technique for increasing the optical strength of single-crystal NaCl and KCl through temperature cycling

This report relates a technique for increasing the optical strength of NaCl and KCl single-crystal samples. The 1.06-micrometer pulsed laser damage thresholds were increased by factors as large as 4.6 for a bulk NaCl single-crystal sample. The bulk laser damage breakdown threshold (LDBT) of the crystal was measured prior to and after heat treatment at 800 degrees C using a Nd:YAG laser operating at 1.06 micrometer. Bulk and surface LDBTs were also studied on samples annealed at 400 degrees C. These samples showed differences in damage morphology on both cleaved and polished surfaces, and the cleaved surfaces had improved damage thresholds. However, neither the polished surfaces nor the bulk showed improved threshold at the lower annealing temperature.