Outlook for Detecting Explosive and Biological Hazards: An Application of THz Technology

摘要

The terahertz (THz) regime, the spectrum lying between the upper limit of conventional electronics (0.1 THz) and the lower limit of photonics (approx10 THz), is rich with emerging possibilities in sensing, imaging and communications. Since it is non-ionizing and difficult to detect, it has particular applications to screening persons for concealed weapons, explosives and biohazards. THz technology, with its ability to "see through" clothing and many types of non-metallic enclosures (and to distinguish skin from metal and plastics) is a promising candidate to address the problem of detecting such concealed threats. Many laboratories generate THz power with mode-locked femtosecond lasers driving photoconductive switches or nonlinear crystals [1, 2], while others multiply the frequency of electronic microwave or millimeter-wave oscillators [3, 4]. Fundamental sources of THz power such as backward-wave oscillators, free-electron and quantum cascade lasers, novel heterojunction diode and transistor circuits, and even micromachined vacuum electronic devices [5] complete the THz toolset.