Introduction to the Special Issue on Terahertz Cameras and Detector Arrays

Abstract

Already an old saying states that “a picture is worth a thousand words”. Imaging allows to obtain complex information in a very compressed, but still comprehensible way—not only in the visible. Terahertz (THz) radiation (0.1–10 THz) features a combination of unique properties, particularly relevant for imaging applications, including penetration through many optically opaque media, (much) higher spatial resolution than in the microwave range due to the shorter wavelength, harmlessness at the available power levels, and even the possibility of “spectroscopic imaging” by fingerprinting of a manifold of resonances that many substances feature in the Terahertz range. Therefore, THz imaging is highly attractive to key applications such as in homeland security, where scanning for suspicious objects hidden in envelopes or beneath clothing allows for threat detection, non-destructive testing of industrial products for quality control, and applications in astronomy where THz radiation can penetrate through stellar dust and nebulas, being able to identify their chemical constituents while visible light or X-rays are severely scattered. Therefore, huge efforts have been undertaken in the past years to develop high sensitivity THz imaging arrays, cameras, and systems; with great progress, yet reaching real-time operation with sufficient dynamic range for many applications. In contrast to the visible, where one technology dominates the market, several approaches are currently followed up in the THz range, tailored to specific target applications. This special issue covers seven invited articles from distinguished groups all around the globe, reviewing the state-of-the art in THz camera development and showing latest results on and technical details of various approaches: