Effects of laser phase noise on the injection of a high-finesse cavity

We study the response of a high-finesse optical cavity to a cw laser during the laser frequency passage through resonance. For a laser that is spectrally larger than the cavity resonance, laser-field phase fluctuations are converted into amplitude fluctuations, and cavity injection is intrinsically noisy. We develop a model based on Schawlow-Townes spontaneous-emission laser broadening and discuss in detail its effects on high-sensitivity spectroscopic techniques such as cavity-enhanced absorption or cavity ring-down spectroscopy. We present realistic simulations of cavity injection during a sweep through resonance and calculation of statistical quantities such as the average injection efficiency. Agreement with experimental observations is established. (C) 2002 Optical Society of America.