Optical external efficiency of terahertz quantum cascade laser based on ??erenkov difference frequency generation

摘要： In this paper, we consider terahertz sources based on ?erenkov di?erence frequency generation in a dual-wavelength mid-infrared quantum cascade laser and calculate analytically the optical external e±ciency of the out-going terahertz wave. The mid-infrared pumps operate simultaneously and have a common upper level. For short cavity lengths and low terahertz losses in the substrate, we ˉnd that implementation of the ?erenkov emission scheme in terahertz di?erence frequency generation quantum cascade lasers improves the optical external e±ciency dramatically. The maximum value of the latter is close to 19%, but is only attainable if the laser exhibits negligible mid-infrared transmission losses.