Czochralski Growth and Characterization of a Novel Nonlinear Optical Crystal Te₂P₂O₉

Abstract

A new nonlinear optical crystal Te2P2O9 (TPO) with dimensions up to 35 × 30 × 20 mm3 was grown successfully by the Czochralski method; the optimal growth parameters are determined. This crystal crystallizes in a monoclinic structure, space group Cc (No. 9), with a three-dimensional framework structure that is constructed of PO4 tetrahedra and TeO5 square pyramid. The transmission spectra suggest that it can transmit well from 0.29 to 4.70 μm. Powder second-harmonic generation (SHG) measurements indicate that TPO is phase-matchable and the SHG efficiency is about 1.3 times that of KDP. The refractive indices revealed a moderate birefringence of 0.13786–0.10615 in the wavelength range of 404.66–1013.98 nm. Thermal analysis shows that TPO has a relatively high specific heat and thermal conductivity, which indicates that TPO has a good thermal stability. The first-principles calculations and dipole moment analysis indicate that optical properties mostly originate from the contribution of TeO5.