Tunable-diode-laser spectroscopy of C₂H₂ using a 3.03 μm GaInAsSb/AlGaInAsSb distributed-feedback laser

The mid-IR region beyond 3 μm is very attractive for gas sensing, since the fundamental absorption bands of several hydrocarbons are located in this range. We demonstrated, for the first time to our knowledge, the use of a novel GaInAsSb/AlGaInAsSb distributed-feedback laser emitting around 3.03 μm in a tunablediode laser-spectroscopy application. The laser operates in continuous mode at room temperature with excellent single-mode and tuning properties. A comparison of the measurement results was made with the recently updated data on ¹²C₂H₂ found in the HITRAN 2008 compilation. A good agreement was found between the measurements and the database. Wavelength modulation spectroscopy of acetylene at ambient conditions was made, and a sensitivity of 18 ppb (parts per billion) per meter at an integration time of 3 s corresponding to a relative absorption of 5 X 10^-6 was obtained. The optimum detection limit of the acetylene measurement in this wavelength modulation spectroscopy setup was better than 1.5 ppb m at an integration time of 600 seconds.