Characterization and properties of infrared NLO crystals: AGeX3 (A=Rb, Cs; X=Cl, Br)

Innovative infrared nonlinear optical crystals AGeX3 were synthesized. Their powder X-ray diffraction patterns demonstrated that they had rhombohedral structures with R3m (no. 160) space group symmetry (except RbGeBr3). Their structural distortion increased with Br content, but decreased with Rb content. The Kurtz powder methods revealed that the nonlinear optical efficiency of CsGeBr3 is 9.64 times that of rhombohedral CsGeCl3 and 28.29 times that of KDP; most importantly, AGeX3 is phase-matchable (except RbGeBr3).