Two-Directional CW THz Wave Generation System by Pumping With a Single Fiber Amplifier of Near-IR Lasers

We constructed a two-directional continuous-wave (CW) terahertz (THz) wave generation system with laser diode pumping. The generation method is based on difference frequency generation (DFG) of two near-infrared (NIR) lasers by excitation of phonon polaritons in a GaP crystal. The two NIR lasers for DFG are amplified simultaneously using one ytterbium-doped fiber amplifier (FA). Efficient beam overlapping of the NIR lasers was achieved on the GaP crystal surface. This system consists of a simple optical design with a single FA. Narrow linewidth CW THz waves, which are generated in two directions, can be applied to high-resolution spectroscopy.