External cavity widely tunable quantum cascade laser based hollow waveguide gas sensors for multianalyte detection

Abstract: In the study presented here, quantitative detection of ethyl chloride, dichloromethane, and trichloromethane individually and in mixture has been demonstrated using an external cavity broadly tunable quantum cascade laser (EC-QCL) based hollow waveguide gas sensor. The EC-QCL has been characterized by coupling into a FT-IR spectrometer documenting sufficient optical power output across a frequency tuning range from 1297cm−1 to 1219cm−1. Concentrations as low as 4 ppb for ethyl chloride, 7ppm for dichloromethane, and 11 ppb for trichloromethane were detected during exponential dilution experiments with the EC-QCL precisely tuned to selective absorption frequencies of the Q-branch for each constituent at 1287.25cm−1, 1262cm−1, and 1220cm−1, respectively. [Copyright &y& Elsevier]