Cavity ringdown spectroscopy: broad band absolute absorption measurements

Here we report further results in our recent extension of cavity ring down spectroscopy (CRDS) to CW single frequency lasers. We previously pointed out the excellent reproducibility of our spectra, in particular the baseline measurements obtained from the empty cavity. The ability of accurately measuring the zero absorption baseline is essential when studying very broad or congested absorption spectra or even continua. We demonstrate the performance of our CW-CRDS setup by obtaining the absolute absorption spectrum of a weak and broad overtone transition in CHF₃. We also discuss how the present results will apply to conventional pulsed-CRDS.