Browsing by Author "Hughes, Lawrence C."

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Hydrogen peroxide detection with quartz-enhanced photoacoustic spectroscopy using a distributed-feedback quantum cascade laser
    (AIP Publishing LLC., 2014) Ren, Wei; Jiang, Wenzhe; Sanchez, Nancy P.; Patimisco, Pietro; Spagnolo, Vincenzo; Zah, Chung-en; Xie, Feng; Hughes, Lawrence C.; Griffin, Robert J.; Tittel, Frank K.
    A quartz-enhanced photoacoustic spectroscopy sensor system was developed for the sensitive detection of hydrogen peroxide (H2O2) using its absorption transitions in the v6 fundamental band at ∼7.73 μm. The recent availability of distributed-feedback quantum cascade lasers provides convenient access to a strong H2O2 absorption line located at 1295.55 cm−1. Sensor calibration was performed by means of a water bubbler that generated titrated average H2O2vapor concentrations. A minimum detection limit of 12 parts per billion (ppb) corresponding to a normalized noise equivalent absorption coefficient of 4.6 × 10−9 cm−1W/Hz1/2 was achieved with an averaging time of 100 s.
  • Thumbnail Image
    Item
    Simultaneous atmospheric nitrous oxide, methane and water vapor detection with a single continuous wave quantum cascade laser
    (The Optical Society, 2015) Cao, Yingchun; Sanchez, Nancy P.; Jiang, Wenzhe; Griffin, Robert J.; Xie, Feng; Hughes, Lawrence C.; Zah, Chung-en; Tittel, Frank K.
    A continuous wave (CW) quantum cascade laser (QCL) based absorption sensor system was demonstrated and developed for simultaneous detection of atmospheric nitrous oxide (N2O), methane (CH4), and water vapor (H2O). A 7.73-µm CW QCL with its wavelength scanned over a spectral range of 1296.9-1297.6 cm−1 was used to simultaneously target three neighboring strong absorption lines, N2O at 1297.05 cm−1, CH4 at 1297.486 cm−1, and H2O at 1297.184 cm−1. An astigmatic multipass Herriott cell with a 76-m path length was utilized for laser based gas absorption spectroscopy at an optimum pressure of 100 Torr. Wavelength modulation and second harmonic detection was employed for data processing. Minimum detection limits (MDLs) of 1.7 ppb for N2O, 8.5 ppb for CH4, and 11 ppm for H2O were achieved with a 2-s integration time for individual gas detection. This single QCL based multi-gas detection system possesses applications in environmental monitoring and breath analysis.