In this paper, DKDP crystals with deuterium content of 55%, 65% and 70% were grown by the traditional
temperature-reduction method. The property including lattice constant, transmittance spectra, Raman spectra, conoscopic
image, and laser damage threshold (LDT) were measured. The results showed that with increasing the degrees of
deuteration for DKDP crystals, the value of lattice parameter a (b) increases and the transmittance also increases in the
range of 350-1800 nm while the laser damage threshold (LDT) decrease. For DKDP crystals, the spectra of Raman
scattering split into two parts and the peak intensity of the totally symmetric PO4 vibration decrease compared with that
of KDP crystals. The homogeneity of the DKDP crystals has not obvious difference.
This paper shows DKDP crystals of different deuterium content are cut for type I non-critical phase-matching with
the direction at 90° to the crystal Z axis (θ=90°) and at 45° to the crystal X axis (Φ=45o), and are measured at the FHG experiments with fundamental frequency wavelength 1064nm and 1053nm, respectively. The optimum deuterium
content of DKDP crystal, that can achieve non-critical phase-matching at FHG experiments, is confirmed by measuring
the relationship of deuterium content and phase-matching angle.
The crucial problem of DKDP crystal for third harmonic generation (THG) is its low laser-induced damage threshold with respect to KDP, which greatly limits energy fluence of the output laser and crystals' useful life. In order to study the relation between wavelength and laser-induced damage of DKDP, we carried out some related experiments in present work. DKDP crystal was conventionally grown from 80%-deuterated solution of high pure materials and the crystal was cut to tripler sample of type II. Laser-induced damage threshold of DKDP crystal for THG was measured under different wavelengths and the effect of laser annealing was also investigated. The experiment shows that laser annealing could obviously improve laser-induced damage threshold of DKDP crystal. The threshold is improved to 1.4, 1.9 or 2.7 times that before annealing for fundamental, second or third harmonic, respectively. Thus laser annealing is an effective approach to enhance laser-induced damage resistance of DKDP crystal.