Using quantum cascade lasers with resonant optical cavities as a diagnostic tool

S. Welzel, G. Lombardi, P.B. Davies, R.A.H. Engeln, D.C. Schram, J. Röpcke

Research output: Chapter in Book/Report/Conference proceedingConference contributionAcademicpeer-review


Absorption spectroscopy based on optical resonators is known to be a very sensitive diagnostic technique. For many years the infrared spectral range could not be employed, because of the lack of suitable radiation sources with the required power and tunability. Recent advances in semiconductor laser technology, in particular the advent of quantum cascade lasers (QCL) provides new possibilities for highly sensitive and selective detection of molecular species. Cavity Enhanced Absorption Spectroscopy (CEAS) with a thermoelectrically (TE) cooled cw QCL emitting at 7.66 µm and employing a ~0.5 m long cavity yielded effective path lengths of 1080 m and a sensitivity of 2 x 10-7 cm-1 Hz-1/2, mainly limited by incomplete averaging over cavity resonances. The molecular concentration detection limit with a 20 s integration time was found to be 6 x 108 molecules/cm3 for N2O and 2 x 10 9 molecules/cm3 for CH4 which is good enough for the selective measurement of trace atmospheric constituents at 2.2 mbar. © 2009 IOP Publishing Ltd
Original languageEnglish
Title of host publicationProceedings of the 3rd International Workshop on Infrared Plasma Spectroscopy, 23–25 July 2008, Greifswald, Germany
EditorsP.B. Davies, J. Röpcke, F. Hempel
Place of PublicationBristol
PublisherInstitute of Physics
Publication statusPublished - 2009

Publication series

NameJournal of Physics: Conference Series
ISSN (Print)1742-6588


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