Regional sensing with an open-path dual comb spectroscopy and a UAS (Conference Presentation)

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 show that this novel spectroscopy source can be employed for regional (~kilometer squared) 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 with the spatial scanning capabilities to enable spatial mapping of atmospheric gas concentrations. The DCS systems measure the atmospheric absorption over long, 100m to 1 km, open air paths with 0.007cm-1 resolution over 1.57 to 1.66 um, covering absorption bands of CO2, CH4, H2O and isotopologues.