A quartz-enhanced photoacoustic spectroscopy sensor for measurement of water vapor concentration in the air<xref ref-type="fn" rid="cpb141171fn1">*</xref>

A quartz-enhanced photoacoustic spectroscopy sensor for measurement of water vapor concentration in the air*

Gong Ping, Xie Liang†, Qi Xiao-Qiong, Wang Rui, Wang Hui, Chang Ming-Chao, Yang Hui-Xia, Sun Fei, Li Guan-Peng

Fig. 4. Double-frequency QTF signal as a function of the modulation frequency. The laser temperature is set at 31 #cod#x00B0;C. The output power of the DFB laser diode is 7 mW.