cw Integrated cavity output spectroscopy

A new approach is described in which continuous, narrow band laser sources are employed with the recently developed integrated cavity output spectroscopy technique to obtain sensitive, quantitative absorption spectra in a simple experimental configuration. Absorption data obtained with cw-ICOS are related to the classical Fabry–Perot intracavity absorption model, which describes why the intracavity absorption is enhanced. A method of continuously injecting cw laser light into the cavity is described, as is a simple means of interpreting the ICOS data to extract accurate absorption intensities. Absorption spectra of vibrational combination bands of CO2 and H2O in the 1.3 μm region are presented.