Microcavity THz quantum cascade laser

We report operation of disk and ring shaped terahertz (THz) quantum-cascade lasers (QCLs) emitting in the THz region between 3.0 and 3.4 THz. The GaAs/Al0.15Ga0.85AsGaAs/Al0.15Ga0.85As 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 900A/cm2 at 5 K. 3D Finite-Difference Time-Domain (FDTD) simulations were performed to obtain the field distributions within a THz QCl resonator at different frequencies.