Pb7F12Cl2: a promising infrared nonlinear optical material with high laser damage threshold

Abstract

This study reports, for the first time, the second-harmonic generation (SHG) property of Pb₇F₁₂Cl₂ as a promising infrared nonlinear optical (NLO) material. Powder second-harmonic generation (SHG) indicates that the compound exhibits phase-matchable SHG properties, which are 1.6 times stronger than those of KH₂PO₄ (KDP). The infrared transmission range could reach 20 μm. The UV absorption indicated that the band gap was about 4.5 eV. A preliminary measurement of laser damage threshold (LDT) is about 80 MW cm⁻², which is much higher than AgGaS₂ (currently commercialized IR NLO material, 5.2 MW cm⁻², measured in the same condition), indicating that Pb₇F₁₂Cl₂ is a potential IR NLO material with high LDT. Theoretical calculations were also performed to elucidate its band structure, electronic configuration and second-order nonlinear coefficients. Particularly, the distinct role of different Pb atoms located in divergent coordinations has also been elaborated using orbital analysis.