Automated high-resolution frequency-stabilized cavity ring-down absorption spectrometer

Abstract

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 continuous wave, single-mode 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 external-cavity diode laser probe 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 less than the free-spectral range. 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 10712cm−1) absorption spectra of water vapor are presented. A frequency resolution of ≈1MHz and minimum measurable line intensity of 10−27cm2cm−1molecule−1 are demonstrated.

Experimental intensity and lineshape parameters of the oxygen A-band using frequency-stabilized cavity ring-down spectroscopy

“…Such limitations must be overcome to support the sub-1% retrieval goals of planned satellite remote sensing observations such as those to be made by NASA's Orbiting Carbon Observatory (OCO) [16][17][18]. The objective of the present work is to extend the O 2 A-band spectroscopic parameters of Brown and Plymate [13] to higher J-values using frequency-stabilized cavity ring-down spectroscopy FS-CRDS [19][20][21][22][23].…”

The air-broadened, near-infrared CO2 line shape in the spectrally isolated regime: Evidence of simultaneous Dicke narrowing and speed dependence

“…47,48 This particular FS-CRDS instrument has been described earlier; 49 therefore, we will discuss only the most salient details herein.…”

Observations of Dicke narrowing and speed dependence in air-broadened CO2 lineshapes near 2.06 μm

“…et al [49][50][51] Briefly, the ring-down cavity was actively locked to a temperature-stabilized HeNe laser with an optical frequency stability of 100 kHz (8 h). The probe laser was a distributedfeedback diode laser (≈3 mW power) centered at 2.055 μm.…”