Coherent imaging with mid-IR and THz quantum cascade lasers through optical feedback interferometry

We retrieve the phase signature in coherent imaging based on a quantum cascade laser (QCL) subjected to optical feedback. In the self-mixing scheme, a single QCL acting as a source and detector of THz radiation, is used to obtain the reflection image of a sample as well as the phase profile without ambiguity. We study the phase sensitivity against optical feedback and assess the limit of the phase signal detection.