As has been known for years, optical imaging systems based on terahertz radiation--which can pass through clothing and other shielding materials--have great potential for security-related applications such as screening at airports. One hindrance to their wider use is the low average output power of most compact terahertz emitters. In their quest to make terahertz systems more practical, engineers at BAE Systems (Nashua, NH) have developed a nonlinear-crystal-based, fiber-laser-pumped terahertz source that produces tunable narrowband radiation with high average power over the 0.8-to-2.45 THz spectral region. Radio frequency (RF) and IR means of generating terahertz radiation were both pursued at BAE Systems, says engineer Daniel Creeden. "However, RF-based technologies seem to severely decrease in efficiency at higher frequencies (above 500 GHz)," he notes.
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