Terahertz quantum-cascade laser operating up to 137 K

We report operation of a terahertz quantum-cascade laser at 3.8 THz $\text{(λ≈79\hspace{0.17em}μ}\mathrm{m})$ up to a heat-sink temperature of 137 K. A resonant phonon depopulation design was used with a low-loss metal–metal waveguide, which provided a confinement factor of nearly unity. A threshold current density of $\text{625\hspace{0.17em}}{\mathrm{A/cm}}^2$ was obtained in pulsed mode at 5 K. Devices fabricated using a conventional semi-insulating surface-plasmon waveguide lased up to 92 K with a threshold current density of $\text{670\hspace{0.17em}}{\mathrm{A/cm}}^2$ at 5 K.