Pulse temporal scaling of LIDT for anti-reflective coatings deposited on lithium triborate crystals.

Anti-reflective (AR) coatings minimize photon losses of optics when it comes to the transmission of light, thus, are broadly used for imaging and laser applications. However, the maximum output power in high-power lasers is limited by the so-called laser-induced damage threshold (LIDT) parameter of optical elements. Often AR coated nonlinear crystals are responsible for such limitations, however, LIDT data is rather scarce. Thus, only limited understanding about LIDT pulse temporal scaling laws for AR coatings exists, which also lacks the specificity about fatigue effect of distinct failure modes. To expand the present knowledge four identical lithium triborate (LBO) crystals were prepared. Each crystal had one side coated with the AR@1064+532 nm coating and the opposite side coated with the AR@355 nm coating. Multiple LIDT tests were then conducted following 1-on-1 and S-on-1 testing protocols at UV and IR wavelengths while varying laser pulse duration. Empirical scaling laws are then investigated for different failure modes and later interpreted using a numerical model.