Optical cavity enhanced real-time absorption spectroscopy of CO₂ using laser amplitude modulation

Dong, Jiahao; Lam, Timothy T.-Y.; Gray, Malcolm B.; Warrington, Richard B; Roberts, Edward H.; Shaddock, Daniel A.; McClelland, David E.; Chow, Jong H.

Optical cavity enhanced real-time absorption spectroscopy of CO₂ using laser amplitude modulation

Date

2014-08-05

Authors

Dong, Jiahao

Lam, Timothy T.-Y.

Gray, Malcolm B.

Warrington, Richard B

Roberts, Edward H.

Shaddock, Daniel A.

McClelland, David E.

Chow, Jong H.

Publisher

American Institute of Physics (AIP)

Abstract

We present a spectrometer based on the cavity enhanced amplitude modulated laser absorption spectroscopy (CEAMLAS) technique for measuring molecular gas absorption. This CEAMLAS spectrometer accurately measured a CO₂ absorption line at 1572.992 nm with effectively 100% measurement duty cycle. It achieved an absorption sensitivity of 5.2 × 10⁻⁹ Hz⁻¹∕² using a linear Fabry-Perot cavity with a modest finesse of ≈1000. We also used the spectrometer to perform preliminary measurements of the ¹³C/¹²C isotopic ratio in CO₂, yielding an isotopic signature δ ¹³C of −83±9‰ for our CO₂ sample.