Multiwavelength diode-laser absorption spectroscopy using external intensity modulation by semiconductor optical amplifiers

Solon Karagiannopoulos*, Edward Cheadle, Paul Wright, Alex Tsekenis, Hugh McCann, Alex Tsekenis

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

A novel opto-electronic scheme for line-of-sight Near-IR gas absorption measurement based on direct absorption spectroscopy (DAS) is reported. A diode-laser-based, multiwavelength system is designed for future application in nonintrusive, high temporal resolution tomographic imaging of H2O in internal combustion engines. DAS is implemented with semiconductor optical amplifiers (SOAs) to enable wavelength multiplexing and to induce external intensity modulation for phase-sensitive detection. Two overtone water transitions in the Near-IR have been selected for ratiometric temperature compensation to enable concentration measurements, and an additional wavelength is used to account for nonabsorbing attenuation. A wavelength scanning approach was used to evaluate the new modulation technique, and showed excellent absorption line recovery. Fixed-wavelength, time-division-multiplexing operation with SOAs has also been demonstrated. To the best of our knowledge this is the first time SOAs have been used for modulation and switching in a spectroscopic application. With appropriate diode laser selection this scheme can be also used for other chemical species absorption measurements. (C) 2012 Optical Society of America

Original languageEnglish
Pages (from-to)8057-8067
Number of pages11
JournalApplied optics
Volume51
Issue number34
DOIs
Publication statusPublished - 1 Dec 2012

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