Watt-range CW powers were achieved over the 3.8-10.8 micron wavelength range. Carrier-leakage suppression and fast carrier extraction allow quantum cascade lasers to reach internal efficiencies near fundamental limits (~ 92 %). Then, CW wall-plug efficiencies ≥ 40 % and powers ≥ 10 W become possible.
We present the latest advances on terahertz quantum-cascade vertical-external-cavity surface-emitting-lasers (VECSELs) that are designed for wide tuning of a single-mode (up to 25% fractional tuning). The enabling component is the amplifying reflectarray metasurface, which allows lasing in Fabry-Perot cavities on very low-order longitudinal modes.