Sub-terahertz Quantum-cascade Laser Source based on Difference-frequency Generation

Authors report a sub-terahertz monolithic semiconductor source based on a high power, long-wavelength quantum cascade laser. In order to obtain higher nonlinear susceptibility in the sub-terahertz frequency region, we design long wavelength dual-upper-state active region in which transition dipole moments are substantially increased. A fabricated device with distributed feedback grating produces nearly watt-level infrared output power, and as a result, it exhibits a peak output power of $18.5 \mu \mathrm{W}$ at room temperature, around a frequency of $\sim700$ GHz. Besides, the device produces an output power of $103 \mu \mathrm{W}$ at 110 K.