High-temperature performance and broad continuous tunability of terahertz quantum-cascade lasers

We demonstrate a terahertz quantum-cascade laser (QCL) operating significantly above the temperature of h nu/k(B), which had so-far been been an empirical limitation for the maximum operating temperature of these devices. With a design that employs a new scattering-assisted injection scheme, a 1.8 THz QCL operating up to a temperature of 1.9h nu/k(B) (163 K) is realized with more than 3 mW of peak optical power output at 150 K. We also demonstrate continuous tunability over a frequency range of 137 GHz of a single-mode QCL operating at 3.8 THz in metal-metal waveguides. A unique concept of altering the lateral mode profile of the "wire laser" waveguide geometry was implemented to achieve tuning despite the strong mode confinement of metal-metal waveguides at terahertz frequencies.