Optical rectification in a BaGa4Se7 crystal for the generation of narrowband terahertz radiation

Narrowband terahertz radiation at 1.97 and 2.34 THz is generated via optical rectification in a BaGa4Se7 crystal. Although broadband terahertz radiation is produced in the crystal, absorption occurs due to the dense phonon mode distribution in the low terahertz frequency regime (i.e. <4 THz), thus resulting in narrowband terahertz radiation exiting the crystal. Since this crystal exhibits numerous non-zero second-order nonlinear tensor elements, generation is investigated for various crystal orientations and excitation polarizations. The BaGa4Se7 crystal exhibits higher spectral densities at the generated frequencies of 1.97 and 2.34 THz in comparison to ZnTe. As such, BaGa4Se7 could provide benefits in the areas of security, communication, medicine, quality control, research, and on-chip applications.