title: Effective utilization of quantum-cascade distributed-feedback lasers in absorption spectroscopy.
abstract: A variable duty cycle quasi-cw frequency scanning technique was applied to reduce thermal effects resulting from the high heat dissipation of type I quantum-cascade lasers. This technique was combined with a 100-m path-length multipass cell and a zero-air background-subtraction technique to enhance detection sensitivity to a parts-in-10(9) (ppb) concentration level for spectroscopic trace-gas detection of CH4, N2O, H2O, and C2H5OH in ambient air at 7.9 micrometers. A new technique for analysis of dense high resolution absorption spectra was applied to detection of ethanol in ambient air, yielding a 125-ppb detection limit.
authors.affiliation: Rice Quantum Institute, Rice University, Houston, Texas 77251-1892, USA. akoster@rice.edu
authors.forename: A A
authors.initials: AA
authors.lastname: Kosterev
authors.forename: R F
authors.initials: RF
authors.lastname: Curl
authors.forename: F K
authors.initials: FK
authors.lastname: Tittel
authors.forename: C
authors.initials: C
authors.lastname: Gmachl
authors.forename: F
authors.initials: F
authors.lastname: Capasso
authors.forename: D L
authors.initials: DL
authors.lastname: Sivco
authors.forename: J N
authors.initials: JN
authors.lastname: Baillargeon
authors.forename: A L
authors.initials: AL
authors.lastname: Hutchinson
authors.forename: A Y
authors.initials: AY
authors.lastname: Cho
mesh_terms: D016902:Air Pollution, Indoor / Q000032:analysis*; D004784:Environmental Monitoring / Q000295:instrumentation*; D004867:Equipment Design; D000431:Ethanol / Q000032:analysis; D005069:Evaluation Studies as Topic; D005740:Gases / Q000032:analysis*; D007834:Lasers; D016014:Linear Models; D008697:Methane / Q000032:analysis; D009609:Nitrous Oxide / Q000032:analysis; D013054:Spectrophotometry, Atomic / Q000295:instrumentation*; D013696:Temperature; D014867:Water / Q000032:analysis
chemical_list: D005740:Gases; D014867:Water; D000431:Ethanol; D009609:Nitrous Oxide; D008697:Methane