Terahertz wave generation via difference frequency generation using 2D In_xGa_1-xSe crystal grown from indium flux

We demonstrate the generation of THz waves (frequency 9.7 THz) using difference frequency generation in an In_xGa_1-xSe mixed crystal grown from In flux. The amount of indium and the lattice constant of the crystal were evaluated using electron micro probe analysis and X-ray diffraction, respectively. We believe that the Ga sites were substituted by In atoms in the In_xGa_1-xSe crystal because the In content, estimated according to the Vegard's law, was similar to that measured by EPMA. The maximum power of the generated THz wave was 39 pJ and the conversion efficiency was 1.7×10^-5 J^-1. This conversion efficiency was 28 times larger than that reported for undoped GaSe crystal.