THz QCL combs under strong RF injection: temporal dynamics and harmonic states

Abstract

In this work present high performance QCL-based THz combs operating on fundamental and harmonic comb states operating up to 110 K in the spectral region from 2 to 4 THz . We employ double-metal, Copper- based laser resonators planarized with a polymer allowing high performance with CW operation up to 118 K . Such waveguide layout allows as well optimized RF coupling facilitating injection of high RF power. We analyze the laser emission by means of SWIFTS technique employing an Hot-Electron-Bolometer based on NbN. Different regimes are observed as the RF injection power is increased, going from FM emission to a pure AM. Spectral bandwidths as large as 700 GHz are observed corresponding to a fully coherent laser operation. For specific waveguide geometries and injection conditions pulses as short as 4 ps are observed. We present as well SWIFTS measurements for THz QCL combs operating on harmonic states under RF injection at the harmonic frequency of 17.6 GHz.