Effects of incomplete light extinction in frequency-agile, rapid scanning spectroscopy

Published

August 1, 2013

Author(s)

David Long, S. Wojtewicz, Joseph T. Hodges

Abstract

The effect of finite beam extinction ratio on the precision and accuracy of cavity ring-down decay time constant measurements was examined using the frequency-agile, rapid scanning, cavity ring-down spectroscopy (FARS-CRDS) technique. This new approach to CRDS uses a waveguide-based electro-optic phase modulator (EOM) to provide a laser beam extinction ratio as high as 80 dB: a value that is ≈30 dB greater than that typically achieved with acousto-optic-modulator-based beam switches. We find that the observed measurement precision scales inversely with extinction ratio, such that an EOM enables measurement of the cavity ring-down decay time with a relative precision of ≈8×10-5. We demonstrate that insufficient extinction can be the dominant cause of statistical uncertainty for extinction ratios below 60 dB. Furthermore, insufficient extinction can result in non-exponential decays, which cause systematic measurement biases in cavity losses and absorption.

Citation

SPIE Proceedings 2013 Defense Security and Sensing Conference

Pub Type

Others

Download Paper

https://doi.org/10.1117/12.2016056

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Keywords

cavity ring-down spectroscopy, optical switch, electro-optic phase modulator

Citation

Long, D. , Wojtewicz, S. and Hodges, J. (2013), Effects of incomplete light extinction in frequency-agile, rapid scanning spectroscopy, SPIE Proceedings 2013 Defense Security and Sensing Conference, [online], https://doi.org/10.1117/12.2016056, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=913765 (Accessed October 10, 2025)