We have investigated the effects of laser bandwidth on quantitative cavity ring-down spectroscopy using the rR transitions of the b(ν = 0)←X(ν = 0) band of molecular oxygen. It is found that failure to account properly for the laser bandwidth leads to systematic errors in the number densities determined from measured ring-down signals. When the frequency-integrated expression for the ring-down signal is fitted and measured laser line shapes are used, excellent agreement between measured and predicted number densities is found.
Joseph T. Hodges, J. Patrick Looney, and Roger D. van Zee, "Laser bandwidth effects in quantitative cavity ring-down spectroscopy," Appl. Opt. 35, 4112-4116 (1996)