Presented in this thesis are experimental and theoretical results for a new type of fiber optic hydrogen sensor based on facet etched nano-apertures in palladium films. Palladium is known to absorb hydrogen, resulting in a change in the optical and structural properties of the film which can be probed by measuring the transmission through the aperture. These sensors showed sensitivity down to 150 ppm in nitrogen with measurable responses in less than one minute. The form factor of this sensor makes it particularly well suited for deployment in unconventional or hard to reach places, such as those found in combustion engines or chemical reactors.The first part of this thesis details current work in the field and the need for accurate hydrogen sensors. Next is the background theory, design, and fabrication of the C-shaped aperture, which is used for its high transmission and resonant behavior. Simulations are used to analyze and engineer the transmission spectrum of the aperture. This is followed by a presentation of experimental results for various C-shaped apertures along with a discussion of fabrication problems and differences, and of the performance of the various sensors. Afterwards, an analysis of theory versus experimental differences is made, specifically regarding the polarization dependence of the aperture and the theoretical hydrogen shift. The response of the sensor is calculated based on known refractive index data, and reasons such as lattice expansion are postulated and examined to explain the discrepancy. Finally, a summary of device performance and fabrication steps is given, and some steps for future work are laid out.
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