Highly sensitive and rugged gas optical detection via interferometric cavity-assisted photothermal spectroscopy

Abstract

We report on the detection of nitric oxide using an Interferometric Cavity-Assisted Photothermal Spectroscopy (ICAPS) gas sensor in combination with a DFB-QCL emitting at 1900 cm-1 as excitation source. In ICAPS, a probe laser is coupled to a Fabry-Perot interferometer acting as an optical transducer of thermal effects. A wavelength modulation approach of the probe diode laser was employed, to actively lock its wavelength to the point of highest sensitivity and linearity of the interferometric fringe for a stable readout. A normalized noise equivalent absorption of 5·10-6 Wcm-1Hz-1/2 was achieved corresponding to 1.4 ppm of NO.