title: Sensitive CH4detection applying quantum cascade laser based optical feedback cavity-enhanced absorption spectroscopy.
abstract: We report on sensitive detection of atmospheric methane employing quantum cascade laser based optical feedback cavity-enhanced absorption spectroscopy (OF-CEAS). An instrument has been built utilizing a continuous-wave distributed feedback quantum cascade laser (cw-QCL) with a V-shaped cavity, a common arrangement that reduces feedback to the laser from non-resonant reflections. The spectrometer has a noise equivalent absorption coefficient of 3.6 × 10-9cm-1Hz-1/2for a spectral scan of CH4at 7.39 μm. From an Allan-Werle analysis a detection limit of 39 parts per trillion of CH4at atmospheric pressure within 50 s acquisition time was found.
authors.forename: N
authors.initials: N
authors.lastname: Lang
authors.forename: U
authors.initials: U
authors.lastname: Macherius
authors.forename: M
authors.initials: M
authors.lastname: Wiese
authors.forename: H
authors.initials: H
authors.lastname: Zimmermann
authors.forename: J
authors.initials: J
authors.lastname: Röpcke
authors.forename: J H
authors.initials: JH
authors.lastname: van Helden