High-power terahertz quantum cascade lasers with ∼0.23 W in continuous wave mode

Terahertz quantum cascade lasers with a record output power up to similar to 0.23 W in continuous wave mode were obtained. We show that the optimal 2.9-mm-long device operating at 3.11 THz has a low threshold current density of 270 A/cm(2) at similar to 15 K. The maximum operating temperature arrived at similar to 65 K in continuous wave mode and the internal quantum efficiencies decreased from 0.53 to 0.19 for the devices with different cavity lengths. By using one convex lens with the effective focal length of 13 mm, the beam profile was collimated to be a quasi Gaussian distribution. (C) 2016 Author(s).