Hydrogen detection using a single palladium nano-aperture on a fiber tip

This chapter discusses the development of fiber optic hydrogen sensors. A motivation for these sensors is given followed by an explanation of the underlying physics of the palladium-hydrogen system. Research results and the strengths and weaknesses of several different fiber optic hydrogen sensor types are discussed. Specifically, the Pd fiber mirror, tapered fiber, Fabry–Pérot interferometer, Fiber Bragg grating, and long period grating sensor architectures are reviewed. Next, a new sensor topology that uses a nano-aperture patterned onto the tip of a Pd coated fiber is presented. The nano-aperture enhances sensitivity because it not only confines light tightly to the Pd surface, but it also creates a Fabry–Pérot resonant structure. Thus, the power shifts in transmission and reflection due to hydrogen induced optical and mechanical changes to the Pd film are amplified. Finally, some conclusions and suggestions for future work are given.