Intracavity THz Polariton Source Using a Shallow-Bounce Configuration

We demonstrate a frequency-tunable THz polariton source based on stimulated polariton scattering (SPS) in MgO:LiNbO
₃
. The system produces THz emission using an intracavity shallow-bounce configuration. Continuously tunable THz emission across the frequency range of 1.05-2.89 THz is demonstrated, and a maximum average THz power of 67.5 μW is detected at 1.34 THz, when pumped with 15.1 W from a continuous-wave laser diode at 880 nm. In contrast to conventional linear configurations, this shallow-bounce configuration offers enhanced THz output power across the systems' entire THz frequency-tuning range, especially at higher frequencies. This is achieved through careful consideration of the THz generation volume, and locating it as close as possible to the emitting surface of the polariton-active crystal, thereby minimizing the deleterious effect of absorption within the SPS crystal. In addition to experimental data, the degree of THz enhancement offered using this configuration, in contrast to a linear configuration is also investigated mathematically.