Rb₂CdBr₂I₂: 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 Rb₂CdBr₂I₂. It crystallizes in the noncentrosymmetric space group Ama2. In the crystal, all the distorted tetrahedron [CdBr₂I₂]^2– 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. Rb₂CdBr₂I₂ showed a powder second harmonic generation (SHG) response 4 times that of KH₂PO₄ (KDP). The preliminary measurement indicated that it exhibits a large laser-induced damage threshold (LDT) of 190 MW/cm² which is 6 times that of AgGaS₂. 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 Rb₂CdBr₂I₂ is a new promising candidate for NLO materials in the IR region.