Frequency tripling of convergent beam with large diameter employing tiling crystals

In inertial confinement fusion laser driver, ultraviolet laser damage of fused silica lens is an important limiting factor for lifting load capability of the laser driver. Considering the above reason, a new configuration of frequency tripling is proposed to solve this problem. The frequency tripling crystal is placed on the back of the focusing lens, thus the sum frequency generation of the fundamental frequency light and doubling frequency light occurs in the beam convergence path. Incident angle of the convergent beam is up to 36.35 mrad, thus the frequency tripling crystal must have a large acceptance angle for phase matching condition. LBO crystal which also has high damage threshold is employed as the frequency tripling crystal. Theoretical analysis indicates that three tiled LBO crystals with different cutting angles will meet the requirement of phase matching and principle experiments also supported this scheme. By employing this configuration, the fused silica lens will only be irradiated by fundamental frequency light and doubling frequency light and its damage threshold will be improved, thus the load capability of the laser driver will be lifted. At the same time, the limitation of growth size with LBO crystal will be broke through.