Open-path gas detection using terahertz time-domain spectroscopy

We report on the development of an experimental setup for remote sensing of gas atmosphere in open air conditions using broadband terahertz pulses. Terahertz time-domain spectroscopy technique is used to solve the problems of gas detection and recognition in the presence of water vapor absorption lines. Acetonitrile vapors were detected and gas concentration was successfully estimated. Organic crystal with a 2% conversion efficiency pumped with near-infrared femtosecond laser pulses was used to generate single-cycle terahertz pulses with energies up to 10 µJ. Application of a novel high-power source of broadband terahertz radiation (0.2–3 THz) opens up new perspectives for further increasing the open space distances in remote sensing problem. (paper)