Resonant-phonon terahertz quantum-cascade laser operating at 2.1 THz (λ≃141 µm)

The development of quantum-cascade lasers (QCLs) at 2.1 THz (λ≃141 µm), which is the longest wavelength QCL to date without the assistance of magnetic fields, is reported. This laser uses a structure based on resonant-phonon depopulation, and a metal–metal waveguide to obtain high modal confinement with low waveguide losses. Lasing was observed up to a heatsink temperature of 72 K in pulsed mode and 40 K in continuous-wave (CW) mode, and 1.2 mW of power was obtained in CW mode at 17 K.