Noncritically phase-matched fourth-harmonic generation of Nd:glass lasers and design of final optics assembly.

The noncritically phase-matched (NCPM) fourth-harmonic generation (FHG) with partially deuterated dihydrogen phosphate (KDP) crystal at an Nd:glass laser radiation wavelength of 1053.1 nm has been confirmed. NCPM FHG has been achieved in 70% and 65% deuterated KDP crystal at the temperature of 17.7°C and 29.3°C, respectively. The angular acceptance of 70% and 65% deuterated KDP crystals fixed at their NCPM temperature were measured, which were 53 and 55 mrad, respectively. The application of the NCPM FHG in a high-power laser facility for inertial confinement fusion is also discussed. Based on the theoretical analysis, the NCPM KDP can be placed after the focus lens; thus, the laser-induced damage of a fused-silica lens at ultraviolet can be avoided.