Compact Quantum Cascade Laser Instrument for Rapid, High Sensitivity Measurements of Trace Gases in Air

We have developed a compact instrument for sensitive, rapid and continuous measurement of trace gases in air, with the focus here on ammonia. This instrument takes advantage of recent technology in quantum cascade (QC) lasers and infrared detectors, which allows high sensitivity to ammonia, 0.2 ppb (0.2times10^-9) of NH₃ in air in 1 s without cryogenic liquids. One may substitute a QC laser operating at a different wavelength to measure other gases. The instrument operates continuously, requiring little operator attention, and web-based remote access is provided for instrument control, calibration and data retrieval. The instrument design includes a thermoelectrically (TE) cooled pulsed QC laser operating at 967 cm^-1, a low volume (0.5 l) multi-pass cell offering 76 meter absorption path length and a TE cooled detector. Integrated software for laser control and data analysis using direct absorption provides quantitative trace gas measurements without calibration gases. The instrument may be applied to field measurements of gases of environmental concern.