Microwave modulation of terahertz quantum cascade lasers: a transmission-line approach

Abstract

We report on microwave impedance measurements of metal-metal ridge-waveguide terahertz quantum cascade lasers. Experimental data, recorded at 4 K in the 100 MHz–55 GHz range, are well reproduced by distributed-parameter transmission-line simulations, showing that the modulation cutoff is limited by the propagation losses that increase for higher microwave frequencies, yielding a 3 dB modulation bandwidth of ∼70 GHz for a 1 mm-long ridge. By using a shunt-stub matching we demonstrate amplitude modulation of a 2.3 THz QCL up to 24 GHz.