Lead Mixed Oxyhalides Satisfying All Fundamental Requirements for High-Performance Mid-Infrared Nonlinear Optical Materials

To design high-performance mid-infrared (mid-IR) nonlinear optical (NLO) materials, we have focused on the combination of a heavy metal lone pair cation, Pb2+ and mixed oxyhalides. A systematic investigation in PbO-PbCl2-PbBr2 system led us to discover the first examples of NLO lead mixed oxyhalides, namely, Pb13O6Cl4Br10, Pb13O6Cl7Br7, and Pb13O6Cl9Br5. All the reported materials have remarkably comprehensive properties including broad IR transparency (up to 14.0 mm), qualified second harmonic generation (SHG) responses (0.6-0.9 AgGaS2), wide band gaps (3.05-3.21 eV), and ease of crystal growth. Interestingly, a centimeter-sized single crystal (2.9 1.3 0.5 cm3) of Pb13O6Cl9Br5 revealing a wide transparent range (0.384-14.0 mm) and high laser damage threshold (LDT) (14.6 AgGaS2) has been successfully grown in an open system. The study suggests that all the reported mixed oxyhalides are outstanding candidates for midIR NLO materials.