High-contrast coherent terahertz imaging of porcine tissue via swept-frequency feedback interferometry.

There is considerable interest in the interrogation of biological tissue at terahertz (THz) frequencies, largely due to the contrast in the optical properties of different biological tissues which occur in this electro-magnetic radiation band. Of particular interest are THz biomedical images, which have the potential to highlight different information than those acquired in other frequency bands, thereby providing an augmented picture of biological structures. In this work, we demonstrate the feasibility of an interferometric biological imaging technique using a THz quantum cascade laser (QCL) operating at 2.59 THz to perform coherent imaging of porcine tissue samples. We show the potential of this new THz biomedical imaging technique for in vivo studies, by virtue of its reflection geometry and useful tissue penetration depth enabled by the large THz powers emitted by the quantum cascade laser used in this work. The observed clustering of interferometric tissue signatures opens a pathway towards automatic techniques for the discrimination of healthy tissue types for the study of normal physiology and possible therapeutic approaches.