Monolithic dual-etalon cavity ring-down spectrometer.

Monolithic dual-etalon cavity ring-down spectrometer.

Modeling and experiments show that it is feasible to perform multiple-species detection at sub-ppm levels with a low-resolution broad-band infrared laser. Target measurement species include CO2, CH, N2O, NO2, SO2, HCl, and CH4, among others, simultaneously, and without process treatment or dehumidification of the exhaust sample—potentially reducing current emission-monitoring costs and the need for extensive sample preparation. Both the photoacoustic spectroscopy and cavity ring-down methods show promise in this regard.

The photoacoustic spectroscopy method in particular is surprisingly sensitive despite its extremely simple configuration, and has the potential to offer an extraordinarily cost-effective platform for multiple-component trace-gas measurements at the sub-ppm level. Due to the dramatic improvement in the measurement sensitivity expected from an increase in the resolution, development of a novel infrared spectrometer has been undertaken.

Significant progress toward developing the first infrared dual-etalon cavity ring-down spectrometer has been achieved, and future work holds the potential to develop revolutionary capabilities in measurement sensitivity for multiple-component systems with this instrument.