A Wide Angle on Chemical Sensing
2014 R&D 100 Winner
Detection and measurement of trace gases at low concentrations, in the presence of dynamically changing contaminants and at significant standoff distances, has important applications in both the civil and defense spaces. The detection and localization of gas releases such as methane from leaking natural gas pipelines or nitrogen oxides from failing electrical equipment requires high sensitivity to the target gas and insensitivity to other atmospheric contaminants, and, ideally, can be performed at long ranges. MIT Lincoln Laboratory’s Wide-Area Chemical Sensor (WACS) system uses a tuned, broadband laser coupled to a lossless, spectrally discriminating receiver to detect gases at sensitivities as good as typical local detectors, at ranges up to tens of kilometers, while compensating for atmospheric contaminants and instrumental drift.
WACS’s enabling technology, a single lossless optical resonant cavity (Fabry-Perot etalon), spectrally separates light that sees the gas of interest from light that doesn’t by tuning the cavity to coincide with the gas absorption. All light encountering the cavity transmits through it or reflects off of it; comparison of these two light intensities allows measurement of the gas-induced absorption, which varies over the bandwidth of the optical cavity’s spectral response for time-varying, but spectrally constant, losses caused by atmospheric scintillation and other atmospheric contaminants.
MIT Lincoln Laboratory
|MIT Lincoln Laboratory's Wide-Area Chemical Sensor (WACS) development team. Front row (l-r): Eric Statz, Jonathan Ashcom and David Schue. Middle row (l-r): Tina Shih, Brian Player and John Zayhowski. Back row (l-r): Alan DeCew and Alexander Wilson.|
The Wide-Area Chemical Sensor (WACS) Development Team from MIT Lincoln Laboratory
Eric R. Statz, Principal Developer