Room temperature, high-efficiency, noncritical phase-matching fourth harmonic generation in partially deuterated ADP crystal

High-efficiency frequency conversion into the deep ultraviolet in a partially deuterated ammonium dihydrogen phosphate (ADP) crystal is reported. For a 60% deuterated ADP crystal, the spontaneous Raman scattering intensity decreased by 38% compared with that of a pristine ADP crystal. At room temperature (24°C), noncritical phase-matching fourth harmonic generation of a 1053 nm laser was realized. The angular acceptance was 55.7 mrad, and the external conversion efficiency from 526 to 263 nm reached 85.3%.