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Optical Engineering

Azimuthal polarization for Raman enhancement in capillary waveguides
Author(s): Jessica C. Mullen; Michael P. Buric; Benjamin T. Chorpening; Steven D. Woodruff
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Paper Abstract

Hollow, metal-lined capillary waveguides have recently been utilized in spontaneous gas-Raman spectroscopy to improve signal strength and response time. The hollow waveguide is used to contain the sample gases, efficiently propagate a pump beam, and efficiently collect Raman scattering from those gases. Transmission losses in the waveguide may be reduced by using an azimuthally polarized pump beam instead of a linearly or radially polarized pump. This will lead to improved Raman signal strength, accuracy, and response time in waveguide-based Raman gas-composition sensors. A linearly polarized laser beam is azimuthally polarized using passive components including a spiral phase plate and an azimuthal-type linear analyzer element. Half-wave plates are then used to switch between the azimuthally polarized beam and the radially polarized beam with no change in input pump power. The collected Raman signal strength and laser throughput are improved when the azimuthally polarized pump is used. Optimization of the hollow waveguide Raman gas sensor is discussed with respect to incident pump polarization.

Paper Details

Date Published: 22 November 2013
PDF: 8 pages
Opt. Eng. 52(11) 117103 doi: 10.1117/1.OE.52.11.117103
Published in: Optical Engineering Volume 52, Issue 11
Show Author Affiliations
Jessica C. Mullen, National Energy Technology Lab. (United States)
Michael P. Buric, National Energy Technology Lab. (United States)
Benjamin T. Chorpening, National Energy Technology Lab. (United States)
Steven D. Woodruff, National Energy Technology Lab. (United States)

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