Generation of narrowband terahertz radiation via phonon mode enhanced nonlinearities in a BaGa₄Se₇ crystal

We report on narrowband terahertz (THz) radiation generation via optical rectification from a BaGa₄Se₇ crystal. The dense phonon mode distribution of the BaGa₄Se₇ crystal causes narrow transmission bands in the THz frequency range with enhanced nonlinear susceptibility magnitudes, thus permitting strong narrowband THz radiation generation at the frequencies of 1.97 and 2.34 THz. In comparison to THz radiation generated from a ZnTe crystal, the narrowband THz radiation produced by the BaGa₄Se₇ crystal is 4.5 times higher at 1.97 THz and 63% higher at 2.34 THz, thus making BaGa₄Se₇ a viable crystal for use in such areas as security and medicine.