Compact sensor for wide concentration range methane and ethane detection employing quartz tuning fork as photodetector in tunable diode laser spectroscopy

We report on a sensor for methane (C1) and ethane (C2) detection employing a quartz tuning fork as a photodetector for tunable diode laser spectroscopy (TDLAS). In this configuration, the QTF is immersed in the gas mixture under investigation within a vacuum-tight cell. Concentrations of methane and ethane in nitrogen-based mixtures ranged from traces up to percent. An interband cascade laser emitting at 3.345 μm was used as light source. Natural gas-like mixtures were generated in 1:10 nitrogen dilution, and gas mixtures composition was retrieved with an accuracy >98%. Decreasing the target gases concentration, minimum detection limits of 770 ppb and 75 ppb for C1 and C2, respectively, were measured at 10 s integration time.