Phase-Matching\nSecond-Harmonic Generation and Enhanced\nLaser-Induced Damage Threshold Induced by Cs Substitution: Cu<sub>3</sub>PSe<sub>4</sub> vs Cs<sub>2</sub>CuP<sub>3</sub>S<sub>9</sub&gt

Chalcophosphates are an important type of infrared nonlinear\noptical\n(NLO) candidates in view of their rich anionic motifs. Here, two copper\nchalcophosphates Cu<sub>3</sub>PSe<sub>4</sub> (CPSe) and Cs<sub>2</sub>CuP<sub>3</sub>S<sub>9</sub> (CCPS) were synthesized and studied\nas IR NLO materials. They both feature three-dimensional polyanionic\nframeworks constructed by similar T2-supertetrahedra, and the structure\nof CCPS can be derived from CPSe via introducing Cs and substituting\nSe with S. This structural evolution results in phase-matchable NLO\nbehavior, enlarged optical band gap, and enhanced laser-induced damage\nthreshold for CCPS. These results are elucidated by structure analysis\nand theoretical calculations, and the increased structural anisotropy\ncontributes to the phase matchable behavior of CCPS. This work presents\na case on how to adjust NLO properties via certain structure considerations,\nwhich may be extended to more systems for obtaining high-performance\nNLO materials.