Pb₁₇O₈Cl₁₈: A Promising IR Nonlinear Optical Material with Large Laser Damage Threshold Synthesized in an Open System

Mid-IR nonlinear optical (NLO) materials are of great importance in modern laser frequency conversion technology and optical parametric oscillator processes. However, the commercially available IR NLO crystals (e.g., AgGaQ₂ (Q = S, Se) and ZnGeP₂) suffer from two obstacles, low laser damage thresholds (LDTs) and the difficulty of obtaining high-quality crystals, both of which seriously hinder their applications. The introduction of Cl, an element with a large electronegativity, and Pb, a relatively heavy element to promote the optical properties, affords an oxide-based IR NLO material, Pb₁₇O₈Cl₁₈ (POC). High-quality POC single crystals with sizes of up to 7 mm × 2 mm × 2 mm have been grown in an open system. Additionally, POC exhibits a large LDT of 408 MW/cm², 12.8 times that of AgGaS₂. POC also exhibits an excellent second harmonic generation response: 2 times that of AgGaS₂, the benchmark IR NLO crystal at 2090 nm, and 4 times that of KDP, the standard UV NLO crystal at 1064 nm. Thus, we believe that POC is a promising IR NLO material.