Study on mid-IR NLO crystals CsGe(BrxCl1−x)3

An innovative infrared nonlinear optical crystal CsGe(BrxCl1−x)3 was synthesized. From its powder X-ray diffraction pattern, this crystal was characterized as a rhombohedral structure with a (R3m, No. 160) space group symmetry. The powder second-harmonic generation (PSHG) measurement of CsGeBr3 showed that its nonlinear optical efficiency is 9.64 times larger than that of rhombohedral CsGeCl3 and is 28.29 times larger than that of KH2PO4 (KDP), and most important of all, that CsGe(BrxCl1−x)3 is phase-matchable. The infrared transparent spectrum of rhombohedral CsGe(BrxCl1−x)3 was extended to more than 30 μm. The rhombohedral CsGe(BrxCl1−x)3 shows the potential in the realm of nonlinear optics and can be applied to the infrared region.