We describe the performance of a sensor system designed for simultaneous detection of multiple chemicals with both broad and narrow absorption features. The sensor system consists of a broadly tunable external cavity quantum cascade laser (ECQCL), multi-pass Herriott cell, and custom low-noise electronics. The ECQCL features a rapid wavelength tuning rate of 2265 cm 1/s (15660 nm/s) over its tuning range of 1150-1270 cm 1 (7.87-8.70 µm), which permits detection of molecules with broad absorption features and dynamic concentrations, while the 0.2 cm-1 spectral resolution of the ECQCL system allows measurement of small molecules with atmospherically broadened absorption lines. High-speed amplitude modulation and low-noise electronics are used to improve the ECQCL performance for direct absorption measurements. We demonstrate simultaneous detection of Freon-134a (1,1,1,2-tetrafluoroethane), ammonia (NH3), and nitrous oxide (N2O) at low-ppb concentrations in field measurements of atmospheric chemical releases from a point source.
Revised: July 25, 2014 |
Published: January 23, 2010
Citation
Phillips M.C., M.S. Taubman, B.E. Bernacki, B.D. Cannon, J.T. Schiffern, and T.L. Myers. 2010.Design and Performance of a Sensor System for Detection of Multiple Chemicals Using an External Cavity Quantum Cascade Laser. In Quantum Sensing and Nanophotonic Devices VII, January 22, 2010, San Francisco, California. Proceedings of the SPIE, edited by M Razeghi, R Sudharsanan and GJ Brown, 7608, Paper No. 76080D. Bellingham, Washington:SPIE.PNNL-SA-69706.doi:10.1117/12.842120