Graduation Year

2007

Document Type

Thesis

Degree

M.S.

Degree Granting Department

Physics

Major Professor

Nicholas Djeu, Ph.D.

Co-Major Professor

Dennis Killinger, Ph.D.

Committee Member

Myung K. Kim, Ph.D.

Keywords

fiber optics, chemical sensor, infrared, evanescent field, spectroscopy

Abstract

This thesis explores the application of coiled sapphire multimode optical fibers for evanescent wave chemical sensing in both the visible spectrum and the near infrared. As has been suggested in the literature pertaining to silica fibers, bending converts low-order modes to high order ones, which leads to more evanescent absorption and thus a more sensitive chemical detector. By coiling the fiber many times, it was expected that even greater sensitivity would be attained.

Experiments were performed to investigate the sensor response to different solutions and to characterize this response. In the first of three experiments, the large absorption peak of water at 3μm was examined in order to compare the sensitivity of a straight fiber versus a coiled one. In the second experiment, the effect of increasing the number of coils was investigated, as was the response of the sensor to varying concentrations of water in heavy water. In the third experiment, methylene blue dye was used to investigate the extent of adsorption of dye molecules on the sapphire fiber and its persistence

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