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EYAL GERECHT, KEVIN O. DOUGLASS, DAVID F. PLUSQUELLIC, NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY, OPTICAL TECHNOLOGY DIVISION, GAITHERSBURG, MD 20899.
Recently developed solid state sources and heterodyne detectors for the terahertz frequency range have made it possible to generate and detect precise digitally synthesized waveforms at THz frequencies with ultra-low phase noise. The sample gas is polarized using sub-µs chirped THz pulses and both the absorption and the free inductive decay (FID) signals are detected using a mixer amplifier multiplier chain. This approach allows for a rapid broadband multi-component detection with low parts-per-billion sensitivities and high frequency accuracy. Current acquisition time is 30 seconds for 10.6 GHz of bandwidth. Such a system can be configured into a portable, robust, and easy to use sensing platform. A full description of broadband trace gas sensor operating at 540 GHz to 620 GHz will be presented.