Effects of incomplete light extinction in frequency-agile, rapid scanning spectroscopy
David Long, S. Wojtewicz, Joseph T. Hodges
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.
SPIE Proceedings 2013 Defense Security and Sensing Conference
, Wojtewicz, S.
and Hodges, J.
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 December 2, 2023)