4.1 Sensitivity and Resolution Limits of Linear Cavity Ring-Down Molecular Spectroscopy with CW Laser Sources

Abstract A non-conventional cavity ring-down spectroscopic technique is de-scribed. When the light intensity is well above the saturation level for the molecular species inside a high-finesse cavity, each single cavity ring-down event simultane-ously measures both the background losses from the cavity mirrors and the linear absorption from the gas. Such a differential scheme acting on very short time scales (a few tens of microseconds) can improve the sensitivity of conventional cavity ring-down by more than one order of magnitude, while achieving sub-Doppler res-olution, if needed. Applications to optical detection of very rare molecular species like radiocarbon dioxide and resolved molecular hyperfine structure in 17O12C16O are presented