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Detecting greenhouse gases in the atmosphere could soon become far easier with the help of an innovative technique developed by a team at NIST, where scientists have overcome an issue preventing the effective use of lasers to rapidly scan samples.
The team, which recently published its findings in Nature Photonics, says the technique also could work for other jobs that require gas detection, including the search for hidden explosives and monitoring chemical processes in industry and the environment.
Research paper cited: G.-W. Truong, K.O. Douglass, S.E. Maxwell, R.D. van Zee, D.F. Plusquellic, J.T. Hodges and D.A. Long. Frequency-agile, rapid scanning spectroscopy. Nature Photonics, DOI: 10.1038/NPHOTON.2013.98, April 28, 2013.
Abstract: Challenging applications in trace gas measurements require low uncertainty and high acquisition rates1, 2, 3, 4. Many cavity-enhanced spectroscopies exhibit significant sensitivity and potential5, 6, but their scanning rates are limited by reliance on either mechanical or thermal frequency tuning7. Here, we present frequency-agile, rapid scanning spectroscopy (FARS) in which a high-bandwidth electro-optic modulator steps a selected laser sideband to successive optical cavity modes. This approach involves no mechanical motion and allows for a scanning rate of 8 kHz per cavity mode, a rate that is limited only by the cavity response time itself. Unlike rapidly frequency-swept techniques8, 9, 10, 11, FARS does not reduce the measurement duty cycle, degrade the spectrum’s frequency axis or require an unusual cavity configuration. FARS allows for a sensitivity of ~2 × 10−12 cm−1 Hz−1/2 and a tuning range exceeding 70 GHz. This technique shows promise for fast and sensitive trace gas measurements and studies of chemical kinetics.