Experimental and theoretical studies on the linear and nonlinear optical properties of lead phosphate crystals LiPbPO4

Abstract

Phosphates with noncentrosymmetric (NCS) structures usually display short ultraviolet (UV) cut-off edges, but often exhibit weak powder second harmonic generation (SHG) intensities. Here we synthesized a NCS-phosphate, LiPbPO₄, that achieves a desired balance between UV transparency, a cut-off edge of about 232 nm, and large SHG activity (about 3 × KDP). The three dimensional (3D) framework of LiPbPO₄ consists of PO₄ and LiO₄ tetrahedra that are corner-shared, forming wide channels where lead cations reside. Local dipole moments for the PO₄ and LiO₄ tetrahedra as well as lead polyhedra in a unit cell were calculated. First-principles calculations have been performed for better understanding the structure–property relationships in LiPbPO₄. In addition, to further explore spatial distribution of the electronic states dominating the NLO activity, the SHG density method was employed.