Temperature dependence of laser-induced damage thresholds for dielectric and metal coatings

In institute of laser engineering, Osaka university, a new high-power laser system by active mirrors with cryogenic cooled Yb:YAG ceramics have been developed for nuclear fusion driver. Because the quasi-three-level nature of Yb at room temperature becomes almost purely four-level at 77 K, the cryogenic cooled Yb:YAG laser system had the slope-efficient of 91.9 %[1]. Laser-induced damage threshold (LIDT) of optical elements is one of important properties because the output power of laser systems is limited by the LIDTs. However, influence of temperature on LIDT is not known well.