Laser induced defect decrement in DKDP crystals varied with photon energy

In this paper, laser induced reactions of bulk defects in DKDP crystals were real-time detected by ultra-microscopy while high power laser irradiation with different photon energy, and the defect elimination processes were observed. It’s found that there were two kinds of bulk defects that can be eliminated: submicron-scale defect and nanoscale defect clusters. The decrement of submicron-scale defects was related to the laser parameters, such as laser fluence and photon energy. The defect decrement could achieve its maximum value at appropriate laser fluence, while the photon energy was fixed. It indicated that up to ~47% of defects could be eliminated by laser irradiation at 3.50eV (355nm). While the laser fluence was fixed, the amount of defects reduced by laser irradiation at 3.50eV was larger than that at 1.17eV (1064nm). The nanoscale defect clusters were hard to be eliminated by laser irradiation at 1.17eV, while most of them could be reduced by laser irradiation at 3.50eV.