External cavity quantum cascade laser-based QEPAS for chlorodifluoromethane spectroscopy and sensing

• DOI: 10.1007/s00340-019-7240-x
• Publication Date: 2019-06-18T06:22:05Z
• Authors: Sheng Zhou; Linguang Xu; Lei Zhang; Tianbo He; Ningwu Liu; Yu Liu; Benli Yu; Jingsong Li
• Keywords: 0103 physical sciences; 01 natural sciences; 7. Clean energy; 3. Good health

Detection of chlorodifluoromethane (R-22) with unresolved rotational–vibrational absorption lines was demonstrated using quartz-enhanced photoacoustic spectroscopy (QEPAS) and an external cavity quantum cascade laser (EC-QCL). A spectral region spanning 1230–1420 cm−1 was measured. A mini quartz tuning fork with high resonance frequency of ~ 75 kHz is first used to improve the QEPAS sensitivity. At a laser optical power of 2 mW, a 1σ-normalized noise-equivalent absorption of 1.9 × 10−8 cm−1 W Hz−1/2 was achieved. The analysis of a mixture of two broadband absorbers (R-22 and acetone) with overlapping absorption spectra was demonstrated. The good linearity response of the measured QEPAS signal amplitude as a function of R-22 concentration indicates the QEPAS-based sensor has a great potential for continuous and noninvasive real-time monitoring of broadband absorbers.