Infrared cavity ringdown laser absorption spectroscopy (IR-CRLAS)

We report the first extension of cavity ringdown laser absorption spectroscopy (CRLAS) into the infrared region. Spectra of static gas samples have been obtained employing a single mode Nd:YAG pumped optical parametric oscillator laser system and are reported for two spectral regions centered around 1.6 and 3.3 μm, respectively. We also explore the issue of the frequency specificity of the ringdown cavity. Specifically, we demonstrate the ability to extract accurate absorption intensities when the width of the spectral feature is much smaller than the free spectral range of the cavity, in direct contrast to recently published theoretical predictions.