High-Power Single-Mode Tapered Terahertz Quantum Cascade Lasers

We demonstrate a series of high output power single-mode terahertz quantum cascade lasers based on semi-insulating surface-plasmon waveguide with tapered geometry structure. The taper half-angle is ranging from 0° to 3°. The tapered waveguide effects on the output power and the laser beam quality are experimentally studied. High single longitudinal mode edge-emission peak powers (92.3 mW) are realized. The peak power monolithically increases with the increasing of the taper angle. All distributed feedback (DFB) lasers lased in the temperature range of 70-75 K. The highest brightness is obtained from the 2° laser. Stable single-mode emissions are realized for DFB lasers with the side-mode suppression ratio $\sim 18$ dB.