Double-metal waveguide terahertz difference-frequency generation quantum cascade lasers with surface grating outcouplers.

We report terahertz quantum cascade laser (QCL) sources based on intra-cavity difference-frequency generation processed into double-metal waveguides with surface-grating outcouplers. This configuration enables high confinement of the terahertz mode in the device active region and efficient surface extraction of terahertz radiation along the entire length of the waveguide. The devices operate at room temperature at 1.9 THz and produce over 110 μW of peak power output with the mid-infrared-to-terahertz conversion of 150 μW/W². The results represent at least a factor of 2 improvement in the performance compared to the best Cherenkov difference-frequency generation QCL devices operating below 2 THz. [ABSTRACT FROM AUTHOR]