Recent development of high power, widely tunable THz quantum cascade laser sources based on difference-frequency generation

We present the recent development of high performance compact THz sources based on intracavity nonlinear frequency mixing in mid-infrared quantum cascade lasers. Significant performance improvements of our THz sources with respect to the continuous wave THz power output, monolithic THz tuning, and widely frequency are achieved by systematic optimization of the device's active region, waveguide design, and chip bonding strategy. Room temperature continuous wave THz power of more than 10 mu W at 3.4 THz is demonstrated at room temperature. Monolithic THz tuning of a chip-based THz source from 2.6 to 4.2 THz with power up to 0.1 mW is achieved. Surface emission from the substrate via a diffraction grating with THz power up to 0.5 mW is also obtained. The developing characteristics show the potential for these THz sources as local oscillators for many astronomical and medical applications.