Simultaneous multi-laser, multi-species tracelevel sensing of gas mixtures by rapidly swept continuous-wave cavity-ringdown spectroscopy

The greenhouse-gas molecules CO₂, CH₄, and H ₂O are detected in air within a few ms by a novel cavity-ring down laser-absorption spectroscopy technique using a rapidly swept optical cavity and multi wavelength coherent radiation from a set of pre-tuned near-infrared diode lasers. The performance of various types of tunable diode laser, on which this technique depends, is evaluated. Our instrument is both sensitive and compact, as needed for reliable environmental monitoring with high absolute accuracy to detect trace concentrations of greenhouse gases in outdoor air.