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Dual-comb spectroscopy for quantification of greenhouse gasses (Conference Presentation)
Author(s): Ian Coddington

Paper Abstract

The output of a laser frequency comb is composed of 100,000+ perfectly spaced, discrete wavelength elements or comb teeth, that act as a massively parallel set of single frequency (CW) lasers with highly stable, well-known frequencies. In dual-comb spectroscopy, two such frequency combs are interfered on a single detector yielding absorption information for each individual comb tooth. This approach combines the strengths of both cw laser spectroscopy and broadband spectroscopy providing high spectral resolution and broad optical bandwidths, all with a single-mode, high-brightness laser beam and a simple, single photodetector, detection scheme. Here we use a DCS systems to measure the atmospheric absorption over long open-air paths with 0.007cm-1 resolution over 1.57 to 1.66 um, covering absorption bands of CO2, CH4, H2O and isotopologues. Inter-comparison of instruments shows that we can measure CO2 and CH4 with precision of 0.14% and 0.35%, respectively, relative to their natural abundance. In addition, this novel spectroscopy source can be employed for regional (~kilometer scale) monitoring using an array of stationed retros or in conjunction with an unmanned aerial systems (UAS). Both fixed and UAS systems combine the high-precision, multi-species detection capabilities of open-path DCS and have proven to be extremely successful at locating and sizing very small gas leaks. Here we focus on two long-term field deployments where a near-IR spectrometer is used to detect methane leaks to support oil and gas and CO2 traffic emissions from the city of Boulder.

Paper Details

Date Published: 12 September 2019
Proc. SPIE 11128, Infrared Remote Sensing and Instrumentation XXVII, 111280E (12 September 2019); doi: 10.1117/12.2531510
Show Author Affiliations
Ian Coddington, National Institute of Standards and Technology (United States)

Published in SPIE Proceedings Vol. 11128:
Infrared Remote Sensing and Instrumentation XXVII
Marija Strojnik; Gabriele E. Arnold, Editor(s)

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