Two-component gas quartz-enhanced photoacoustic spectroscopy sensor based on time-division multiplexing of...

A two-component gas sensor in quartz-enhanced photoacoustic spectroscopy based on time-division multiplexing (TDM) technology of a distributed-feedback (DFB) laser driver current was proposed and experimentally demonstrated. The quartz tuning-fork-based photoacoustic spectroscopy (PAS) cell configuration with two optical collimators and two acoustic microresonators was designed to detect the second-harmonic (${2}f$2f) PAS signal. The two optical collimators guaranteed that the two laser beams would inject the PAS cell conveniently, providing higher power input than a 3 dB optical fiber coupler. Two-component gas sensing was achieved by the TDM of the DFB laser driver current. We used this two-component gas sensing technique to detect acetylene (${{\rm C}_2}{{\rm H}_2}$C₂H₂) at 1532.83 nm and methane (${{\rm CH}_4}$CH₄) at 1653.722 nm. The ${{\rm C}_2}{{\rm H}_2}$C₂H₂ and ${{\rm CH}_4}$CH₄ detection was achieved at a 2.4 s interval. The minimum detection limits of 1 ppmv for ${{\rm C}_2}{{\rm H}_2}$C₂H₂ and 13.14 ppmv for ${{\rm CH}_4}$CH₄ were obtained, and the linear responses reached were 0.99968 and 0.99652 for ${{\rm C}_2}{{\rm H}_2}$C₂H₂ and ${{\rm CH}_4}$CH₄, respectively. Moreover, the continuous monitoring of ${{\rm CH}_4}$CH₄ and ${{\rm C}_2}{{\rm H}_2}$C₂H₂ for 40 min showed a good stability. The TDM technology of the DFB laser driver current would play an important role on the multi-component detection.