A pulsed quantum-cascade distributed feedback laser operating at near room temperature was used for sensitive high-resolution IR absorption spectroscopy of ambient air at a wavelength of ~8 μm. Near-transform-limited laser pulses were obtained owing to short (~5-ns) current pulse excitation and optimized electrical coupling. Fast and slow computer-controlled frequency scanning techniques were implemented and characterized. Fast computer-controlled laser wavelength switching was used to acquire second-derivative absorption spectra. The minimum detectable absorption was found to be 3 × 10<sup>−4</sup> with 10<sup>5</sup> laser pulses (20-kHz repetition rate), and 1.7 × 10<sup>−4</sup> for 5 × 10<sup>5</sup> pulses, based on the standard deviation of the linear regression analysis.
© 2000 Optical Society of America
(010.1280) Atmospheric and oceanic optics : Atmospheric composition
(140.5960) Lasers and laser optics : Semiconductor lasers
(280.3420) Remote sensing and sensors : Laser sensors
(300.6320) Spectroscopy : Spectroscopy, high-resolution
Anatoliy A. Kosterev, Frank K. Tittel, Claire Gmachl, Federico Capasso, Deborah L. Sivco, James N. Baillargeon, Albert L. Hutchinson, and Alfred Y. Cho, "Trace-Gas Detection in Ambient Air with a Thermoelectrically Cooled, Pulsed Quantum-Cascade Distributed Feedback Laser," Appl. Opt. 39, 6866-6872 (2000)