We have demonstrated quantitative chemical vapor detection with a multimode quantum cascade (QC) laser. Experiments incorporated pseudorandom code (PRC) modulation of the laser intensity to permit sensitive absorption measurements of isopropanol vapor at 8.0µ . The demonstration shows the practicality of one technical approach for implementing low-peak-power QC lasers in the transmitter portion of a differential absorption lidar (DIAL) system. With a 31-chip, 300-ns/chip PRC sequence, the measured isopropanol detection limit was 12 parts in 106 by volume times meters (~3×10-3 absorption) for a simple backscatter-absorption measurement configuration.
© 2000 Optical Society of America
[Optical Society of America ]
C. M. Gittins, E. T. Wetjen, C. Gmachl, F. Capasso, A. L. Hutchinson, D. L. Sivco, J. N. Baillargeon, and A. Y. Cho, "Quantitative gas sensing by backscatter-absorption measurements of a pseudorandom code modulated λ ~ 8-µm quantum cascade laser," Opt. Lett. 25, 1162-1164 (2000)