Microcavity terahertz quantum-cascade laser

We report the realization of microdisk and microring quantum-cascade lasers (QCLs) emitting in the terahertz (THz) region between 3.0 THz and 3.8 THz. The GaAs/Al 0.15 Ga 0.85 As heterostructure is based on longitudinal-optical phonon scattering for depopulation of the lower radiative state. A double metal waveguide is used to confine the whispering gallery modes in the gain medium. The threshold current density is 900 A/cm 2 at 5 K. Lasing takes place in pulsed-mode operation up to a heat-sink temperature of 140 K. Finite-Difference Time-Domaine (FDTD) simulations were performed in a strong field limit to obtain the field distribution within a microdisk THz QCL resonator.