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PubMed · 16608568

Water-vapor detection using asynchronous THz sampling.

Michael S Brown·Gregory J Fiechtner·J V Rudd·David A Zimdars·Matthew Warmuth·James R Gord
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Abstract

The use of a fiber-coupled terahertz (THz) transmitter/receiver pair for spectroscopic detection of water vapor is investigated. Transmission signals of an alumina cylinder demonstrate that the measurement approach can be applied in a windowless ceramic combustor. First, a conventional commercial transmitter/receiver pair is used to make measurements for frequencies to 1.25 THz. Water-vapor absorption is clearly evident within the alumina transparency window and is readily modeled using existing databases. A variety of data-acquisition schemes is possible using THz instrumentation. To assess signal-collection techniques, a prototype THz transmitter/receiver pair is then used with the asynchronous optical-sampling (ASOPS) technique to obtain asynchronous THz-sampling signals to 1 THz without the need for an optomechanical delay line. Two mode-locked Ti:sapphire lasers operating at slightly different repetition rates are used for pumping the transmitter and receiver independently to permit a complete time-domain THz signal to be recorded. The resulting repetitive phase walkout is demonstrated by collecting power spectra of room air that exhibit water-vapor absorption.

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AbsorptionLasersSpectrophotometry, InfraredTime FactorsVolatilizationWaterJournal ArticleResearch Support, U.S. Gov't, Non-P.H.S.

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Michael S Brown, Gregory J Fiechtner, J V Rudd, David A Zimdars, Matthew Warmuth, James R Gord. 2006. Water-vapor detection using asynchronous THz sampling.. https://doi.org/10.1366/000370206776342670

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