A compact QCL based methane and nitrous oxide sensor for environmental and medical applications

Abstract

A methane (CH₄) and nitrous oxide (N₂O) sensor based on a sensitive, selective and well established technique of quartz enhanced photoacoustic spectroscopy (QEPAS) was developed for environmental and biomedical measurements. A thermoelectrically cooled (TEC) distributed feedback quantum cascade laser (DFB-QCL), capable of continuous wave (CW) mode hop free emission in the 7.83 μm wavelength range, was used as an excitation source. For the targeted CH₄ and N₂O absorption lines located at 1275.04 cm⁻¹ and 1275.49 cm⁻¹ detection limits (1σ) of 13 ppbv and 6 ppbv were achieved with a 1 second data acquisition time, respectively. Environmental data of CH₄ and N₂O mixing ratios acquired using the QEPAS sensor system are also reported.