A compact system for methane sensing based on the Quartz-Enhanced Photoacoustic Spectroscopy
technique has been developed. This development has been taken through two versions which were based
respectively on a Fabry Perot quantum wells diode laser emitting at 2.3 lm, and on a quantum wells
distributed feedback diode laser emitting at 3.26 lm. These lasers emit near room temperature in the
continuous wave regime. A spectrophone consisting of a quartz tuning fork and one steel microresonator
was used. Second derivative wavelength modulation detection was used to perform low methane
concentration measurements. The sensitivity and the linearity of the QEPAS sensor were studied. A
normalized noise equivalent absorption coefficient of 7.26 106 cm1 W/Hz1/2 was achieved. This
corresponds to a detection limit of 15 ppmv for 12 s acquisition time.