Rb<sub>2</sub>CdBr<sub>2</sub>I<sub>2</sub>: A New IR Nonlinear Optical Material with a Large Laser Damage Threshold

This paper describes the synthesis, crystal structure, and photophysical properties of a new compound Rb<sub>2</sub>CdBr<sub>2</sub>I<sub>2</sub>. It crystallizes in the noncentrosymmetric space group <i>Ama</i>2. In the crystal, all the distorted tetrahedron [CdBr<sub>2</sub>I<sub>2</sub>]<sup>2–</sup> groups are arranged in a way such that all the Cd–I bonds are located in the same side of the Cd atoms resulting in a net polarization. Rb<sub>2</sub>CdBr<sub>2</sub>I<sub>2</sub> showed a powder second harmonic generation (SHG) response 4 times that of KH<sub>2</sub>PO<sub>4</sub> (KDP). The preliminary measurement indicated that it exhibits a large laser-induced damage threshold (LDT) of 190 MW/cm<sup>2</sup> which is 6 times that of AgGaS<sub>2</sub>. It also exhibits a wide transparent region (0.37–14 μm) with a relatively high (up to 490 °C) thermal stability. All these indicate that Rb<sub>2</sub>CdBr<sub>2</sub>I<sub>2</sub> is a new promising candidate for NLO materials in the IR region.