We describe a frequency-stabilized cavity ring-down absorption spectrometer with automated scanning capabilities. The system utilizes the comb of ring-down cavity resonances as frequency markers for spectral scans. The comb is actively stabilized with respect to a frequency-stabilized reference laser, and the probe laser frequency is in turn actively stabilized with respect to resonances of the ring-down cavity frequency comb. Ring-down spectra are obtained by locking the probe laser to sequential cavity resonances (separated by the ring-down cavity free spectral range), and the ring-down cavity frequency comb is translated by controlled amounts using acousto-optic frequency shifting methods for fine frequency steps (to enable sub-free-spectral range step sizes). A computer-controlled method for automating frequency tuning and probe laser locking to the cavity resonances is described, and high-resolution near-infrared (vicinity of 10712 cm-1) absorption spectra of water vapor are presented. A frequency resolution of approximately 1 MHz and minimum measurable line intensity of 10-27 cm2 cm-1 molec-1 are demonstrated.
Review of Scientific Instruments
absorption, cavity ring-down spectroscopy, optical resonator, water vapor
and Ciurylo, R.
Automated High-Resolution Frequency-Stabilized Cavity Ring-Down Absorption Spectrometer, Review of Scientific Instruments
(Accessed November 28, 2023)