We describe the design, construction, and initial performance evaluation of a high-repetition-rate cavity ringdown spectrometer. The spectrometer is based on the use of the Pound-Drever-Hall technique to lock the laser frequency to the maximum of a transmission fringe of the interferometer used as a sample cell. This results in continuous injection of light into the interferometer. The injection is repetitively interrupted with an acousto-optical modulator to generate ringdowns (exponential decays) at a typical rate of 10 kHz. Averaging of these large numbers of fitted ringdown times allows us to attain a minimum detectable absorption of 1.43×10<sup>−11</sup> cm<sup>−1</sup> Hz<sup>−1/2</sup> short term and 9.0×10<sup>−11</sup> cm<sup>−1</sup> Hz<sup>−1/2</sup> long term. In addition, the spectrometer has a continuous tuning capability of ∼1 cm<sup>−1</sup>, which allows the use of standard linearization and frequency calibration techniques for the spectrum. To illustrate the operation and sensitivity of the spectrometer, part of the Q-branch of a weak acetylene overtone has been recorded.
© 2006 Optical Society of America
(120.6200) Instrumentation, measurement, and metrology : Spectrometers and spectroscopic instrumentation
(300.6340) Spectroscopy : Spectroscopy, infrared
(300.6390) Spectroscopy : Spectroscopy, molecular
Original Manuscript: September 1, 2005
Manuscript Accepted: October 17, 2005
R. Z. Martínez, Markus Metsälä, Olavi Vaittinen, Tommi Lantta, and Lauri Halonen, "Laser-locked, high-repetition-rate cavity ringdown spectrometer," J. Opt. Soc. Am. B 23, 727-740 (2006)