Terahertz imaging using quantum cascade lasers: a review of systems and applications
The terahertz (THz) frequency quantum cascade laser (QCL) is a compact source of THz radiation offering high power, high spectral purity and moderate tunability. As such, these sources are particularly suited to the application of THz frequency imaging across a range of disciplines, and have motivated significant research interest in this area over the past decade. In this paper we review the technological approaches to THz QCL based imaging and the key advancements within this field. We discuss in detail a number of imaging approaches targeted to application areas including multiple frequency transmission and diffuse reflection imaging for the spectral mapping of targets; as well as coherent approaches based on the self mixing phenomenon in THz QCLs for long range imaging, three dimensional imaging, materials analysis, and high resolution inverse synthetic aperture radar imaging.