Effect of metal doping on the laser induced damage of KDP crystals: a first-principles study

KH2PO4 (KDP) crystal is a kind of widely used nonlinear optical material, but its manufacturing process produces various defects which influence the laser induced damage threshold (LIDT) of the KDP crystal. This work studies the influence of the metal doping defects (Na, Cr, Co, Ni, Zn and Pb) on the stability, electronic structure, optical and mechanical properties of KDP crystal by the density functional theory (DFT) calculation. Results show that the change of lattice parameters and bond lengths, and the formation energies of the metal doped KDP have close relationship with the radius of the doped metal atoms. The electronic and optical calculations show that the Na doping defects have little effect on the energy band and optical properties of KDP crystals, but Cr, Zn and Pb doping defects show large optical absorption peaks. Meanwhile, the Cr, Co, Ni and Pb atoms have great influence on the mechanical properties of the KDP. Therefore, the KDP synthesis process needs to pay particular attention to control Cr and Pb doping defects to avoid decreasing the LIDT of KDP. This work explains the effect of metal doping on the laser damage resistance of KDP crystals and provides a theoretical basis for enhancing the performance of KDP crystals.