A broadband cavity ring-down spectrometer for the near infrared

Cavity ring-down (CRD) spectroscopy, a highly sensitive technique for detecting weak absorbance, has been in active development since first being reported in 1988 by O´Keefe and Deacon. Monochromatic detection is prone to cross sensitivities and can only address a single liquid or gaseous component. In contrast, broadband approaches allow for the simultaneous analysis of different species within a mixture, e.g. in complex samples such as atmospheric gas or breath gas. Stelmaszcyk et al. [2] report on the development of a broadband CRD spectrometer for the visible spectral range based on a white-light supercontinuum source. Since more gases of interest absorb in the near infrared (NIR) spectral range, broadband CRD spectroscopy in the NIR is particularly useful for investigating gases. The spectrometer reported on here is intended to be used for the analysis of gases. To the best of our knowledge, this is the first publication to present results obtained with NIR CRD spectroscopy that might be used for the simultaneous detection of various gases such as methane, carbon dioxide and water.