Rapid growth of a large size, highly deuterated DKDP crystal and its efficient noncritical phase matching fourth-harmonic-generation of a Nd:YAG laser

Abstract

A high quality, large size (100 × 105 × 96 mm³) deuterated potassium dihydrogen phosphate (DKDP) crystal with high deuterium content was successfully grown by the rapid growth method. A noncritical phase matching (NCPM) fourth-harmonic-generation (FHG) of Nd:YAG laser (1064 nm) was realized at 39.7 °C or so. The smallest full width at half maximum (FWHM) of angular acceptance for the longest crystal sample (20 mm) is 33.5 mrad, which is 10 times larger than the value of critically PM of a KDP crystal. The FHG conversion efficiency increases with the crystal length and reaches 64% for the 20 mm long crystal. As we have known, this is the highest FHG conversion efficiency of a 1064 nm laser with a repetition rate of 10 Hz in low drive conditions.