Terahertz imaging through self-mixing in a quantum cascade laser

We demonstrate terahertz (THz) frequency imaging through use of a single quantum cascade laser (QCL) device for both generation and sensing of THz radiation. Detection is achieved by utilising the effect of self-mixing in the QCL, and specifically by monitoring perturbations to the voltage across the QCL induced by light reflected from an external object back into the laser cavity. Self-mixing imaging offers high sensitivity, a potentially fast response, and a simple, compact optical design, and we show that it can be used to obtain high-resolution reflection images of exemplar structures.