Magnetic field effects in terahertz quantum-cascade lasers

We have measured the emission intensity and spectra of terahertz quantum-cascade lasers in an external magnetic field applied normal to the epilayers. We have observed a reduction of the threshold current, an enhancement of laser emission intensity and shifts of the emission line. A wider operating range was predicted for the selected waveguide design according to our finite-difference time-domain simulation results. The intensity enhancement and the threshold current reduction are attributed to the suppression of nonradiative Auger-intersubband transitions by Landau quantization of the in-plane electron motion, to the modulation of the injection rate via resonant inter-Landau-level transfer, and to the modulation of waveguide properties.