Symmetrically tapered <30-micron-thick quasi-planar Ge waveguides as chemical sensors for microanalysis

Vongsvivut, Jitraporn, Shilov, Sergey V., Ekgasit, Sanong and Braiman, Mark S. 2002, Symmetrically tapered <30-micron-thick quasi-planar Ge waveguides as chemical sensors for microanalysis, Applied spectroscopy, vol. 56, no. 12, pp. 1552-1561.


Title Symmetrically tapered <30-micron-thick quasi-planar Ge waveguides as chemical sensors for microanalysis
Alternative title Symmetrically tapered <30-μm-thick quasi-planar germanium waveguides as chemical sensors for microanalysis
Author(s) Vongsvivut, Jitraporn
Shilov, Sergey V.
Ekgasit, Sanong
Braiman, Mark S.
Journal name Applied spectroscopy
Volume number 56
Issue number 12
Start page 1552
End page 1561
Total pages 10
Publisher Society for Applied Spectroscopy
Place of publication Frederick, Md.
Publication date 2002-12
ISSN 0003-7028
1943-3530
Keyword(s) bacteriorhodopsin (bR)
D96N mutant
evanescent wave sensor
hair analysis
nujol
sensitivity
tapered Ge waveguides
throughput
Summary Symmetrically tapered planar IR waveguides have been fabricated by starting with a ZnS coated concave piece of single-crystal Ge, embedding it in an epoxide resin as a supporting substrate, and then grinding and polishing a planar surface until the thickness at the taper minimum is <30 μm. Such tapering is expected to enhance a waveguide's sensitivity as an evanescent wave sensor by maximizing the amount of evanescent wave energy present at the thinnest part of the waveguide. As predicted by theory, the surface sensitivity, i.e., the absorbance signal per molecule in contact with the sensing region, increases with decreasing thickness of the tapered region even while the total energy throughput decreases. The signal-to-noise ratio obtained depends very strongly on the quality of the polished surfaces of the waveguides. The surface sensitivity is superior to that obtained with a commercial Ge attenuated total reflection (ATR) accessory for several types of sample, including thin films (<10 ng) and small volumes (<1 μL) of volatile solvents. By using the waveguides, light-induced structural changes in the protein bacteriorhodopsin were observable using samples as small as ∼50 pmol (∼1 μg). In addition, the waveguide sensors can reveal the surface compositions on a single human hair, pointing to their promise as a tool for forensic fiber analysis.
Language eng
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
Persistent URL http://hdl.handle.net/10536/DRO/DU:30038962

Document type: Journal Article
Collection: School of Life and Environmental Sciences
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