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Proceedings Paper

On the accuracy of decay constant measurement by swept-cavity heterodyne cavity ringdown spectroscopy
Author(s): K. K. M. B. Dilusha Silva; Aislinn van der Walt; John M. Dell; Lorenzo Faraone
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Paper Abstract

Cavity ringdown spectroscopy (CRDS) measures the decay time, of a resonant optical cavity containing a measurand, as a function of optical frequency. The measurand is identified and quantified by the cavity decay time, which is modified by the measurand within. As coupling light into a high-finesse optical cavity is difficult, the throughput of the cavity is small. A recent variant, swept-cavity heterodyne CRDS, interferes backward escaping cavity light, with light reflected from the cavity input mirror, providing better signal sensitivity due to the heterodyne advantage. The measured interference signal is demodulated and log-amplified to produce a signal whose slope is representative of the cavity decay time. This paper, for the first time, examines the conditions required for high-fidelity measurements of the cavity decay time using swept-cavity heterodyne CRDS and log-amplification technique. We demonstrate that, due to the very large bandwidth and dynamic range of the log-amplifier, for realistic measurement conditions, the log-amplifier does not impose any significant restrictions on the measurement accuracy. We also demonstrate, however, the measurement accuracy is limited by two factors, the detector bandwidth, and segment of acquired data used to measure the slope.

Paper Details

Date Published: 12 May 2011
PDF: 8 pages
Proc. SPIE 8032, Next-Generation Spectroscopic Technologies IV, 80320F (12 May 2011); doi: 10.1117/12.883601
Show Author Affiliations
K. K. M. B. Dilusha Silva, The Univ. of Western Australia (Australia)
Aislinn van der Walt, The Univ. of Western Australia (Australia)
John M. Dell, The Univ. of Western Australia (Australia)
Lorenzo Faraone, The Univ. of Western Australia (Australia)

Published in SPIE Proceedings Vol. 8032:
Next-Generation Spectroscopic Technologies IV
Mark A. Druy; Richard A. Crocombe, Editor(s)

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