Characterization of supported cylinder-planar germanium waveguide sensors with synchrotron Infrared radiation

Vongsvivut, Jitraporn, Fernandez, Jason, Ekgasit, Sanong and Braiman, Mark S. 2004, Characterization of supported cylinder-planar germanium waveguide sensors with synchrotron Infrared radiation, Applied spectroscopy, vol. 58, no. 2, pp. 143-151, doi: 10.1366/000370204322842869.

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Title Characterization of supported cylinder-planar germanium waveguide sensors with synchrotron Infrared radiation
Author(s) Vongsvivut, Jitraporn
Fernandez, Jason
Ekgasit, Sanong
Braiman, Mark S.
Journal name Applied spectroscopy
Volume number 58
Issue number 2
Start page 143
End page 151
Total pages 9
Publisher Society for Applied Spectroscopy
Place of publication Frederick, Md.
Publication date 2004-02
ISSN 0003-7028
Keyword(s) tapered waveguides
evanescent wave absorption spectroscopy
synchrotron IR radiation
blackbody IR source
Summary Cylinder-planar Ge waveguides are being developed as evanescent-wave sensors for chemical microanalysis. The only non-planar surface is a cylinder section having a 300-mm radius of curvature. This confers a symmetric taper, allowing for direct coupling into and out of the waveguide's 1-mm2 end faces while obtaining multiple reflections at the central <30-μm-thick sensing region. Ray-optic calculations indicate that the propagation angle at the central minimum has a strong nonlinear dependence on both angle and vertical position of the input ray. This results in rather inefficient coupling of input light into the off-axis modes that are most useful for evanescent-wave absorption spectroscopy. Mode-specific performance of the cylinder-planar waveguides has also been investigated experimentally. As compared to a blackbody source, the much greater brightness of synchrotron-generated infrared (IR) radiation allows a similar total energy throughput, but restricted to a smaller fraction of the allowed waveguide modes. However, such angle-selective excitation results in a strong oscillatory interference pattern in the transmission spectra. These spectral oscillations are the principal technical limitation on using synchrotron radiation to measure evanescent-wave absorption spectra with the thin waveguides.
Language eng
DOI 10.1366/000370204322842869
Field of Research 030107 Sensor Technology (Chemical aspects)
Socio Economic Objective 970103 Expanding Knowledge in the Chemical Sciences
HERDC Research category C1.1 Refereed article in a scholarly journal
Copyright notice ©2004, Society for Applied Spectroscopy
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Document type: Journal Article
Collection: School of Life and Environmental Sciences
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