We demonstrate a simple periodically locked cw cavity ringdown spectroscopy technique that enables a very large number of ringdown events to be rapidly acquired. An external cavity diode laser is locked to a high-finesse cavity, and as many as 16,000 ringdown events per second are obtained by periodically switching off the light entering the high-finesse cavity. Following each ringdown event, the light to the cavity is switched back on and cavity lock is rapidly reacquired. Limited only by our relatively modest digitization rate, we obtained a minimum detectable absorption loss of 4.7 × 10<sup>−9</sup> cm<sup>−1</sup>, but we show that faster digitization could provide a sensitivity of 5.9 × 10<sup>−10</sup> cm<sup>−1</sup> Hz<sup>−1/2</sup>.
© 2003 Optical Society of America
(020.0020) Atomic and molecular physics : Atomic and molecular physics
(120.0120) Instrumentation, measurement, and metrology : Instrumentation, measurement, and metrology
(140.2020) Lasers and laser optics : Diode lasers
(300.0300) Spectroscopy : Spectroscopy
Nicola J. van Leeuwen, Jan C. Diettrich, and Andrew C. Wilson, "Periodically Locked Continuous-Wave Cavity Ringdown Spectroscopy," Appl. Opt. 42, 3670-3677 (2003)