Simultaneous detection of atmospheric CH_4 and CO using a single tunable multi-mode diode laser at 233 μm

Abstract

We report on the first application (to our knowledge) of an extended-wavelength (2.33 μm) multi-mode diode laser for simultaneous measurement of the concentrations of CH(4) and CO in the ambient air. The signals identification and quantitative analysis are performed using correlation spectroscopy. A Herriott cell and the wavelength modulation spectroscopy technique with second harmonic detection are also utilized to improve the detection sensitivity of the system. The detection limits of the system are estimated to be about 81 ppbv and 31 ppbv for CH(4) and CO, respectively. The accuracy, sensitivity, precision, and stability are also analyzed to confirm the potential of the system.