Continuous-Wave Reflection Imaging Using Optical Feedback Interferometry in Terahertz and Mid-Infrared Quantum Cascade Lasers

In this paper, we investigate a coherent imaging system based on Terahertz and mid-infrared (MIR) quantum cascade lasers (QCLs) in terms of phase sensitivity against optical feedback. In the self-mixing scheme, a single QCL acting as oscillator, mixer and detector of infrared radiation, is used for continuous-wave reflection imaging as well as phase profiling. We study the dependence of the phase signature on the optical feedback level and assess the limit for phase signal detection.