Research on the growth interfaces of pyramidal and prismatic sectors in rapid grown KDP and DKDP crystals

Abstract

Rapid grown KDP and DKDP crystals have obvious phase jump at the pyramid–prism (PY-PR) interfaces, which will give rise to intensity modulation to the propagation beam. In this paper, the basic properties of phase jump at the PY-PR interfaces in rapid grown KDP and DKDP crystals are firsly characterized and compared. Then, the influence of the interface’s phase jump on the third harmonic beam modulation is researched by the third-harmonic-generation (THG) experiment. It is found that there exist two PY-PR interfaces in the KDP crystal (SHG1 and SHG2) shaping a “bamboo hat” and three PY-PR interfaces in the DKDP crystal (THG1, THG2 and THG3) shaping a “basin”. The phase-jump magnitude of the PY-PR interface in DKDP crystal is about 1.8 times larger than that in KDP crystal. The THG1 interface, at the bottom of the “basin”, has the largest root-mean-squared gradient (GRMS) of the phase jump, which arouses about 1.6 times modulations to the THG beam. To suppress the beam modulation, the GRMS of phase jump at the PY-PR interface is suggested below 1.2 λ/mm.