Reflective Palladium Nanoapertures on Fiber for Wide Dynamic Range Hydrogen Sensing

We present detailed experimental results on a reflective fiber sensor that is capable of accurately quantifying the hydrogen concentration over a wide dynamic range that spans from 1% down to 90 ppm. The sensor consists of a 'C' shaped nano-Aperture etched into the facet of a palladium coated optical fiber. Hydrogen changes the intensity and phase delay of the field reflected by the aperture differently than for the surrounding film and thus it greatly affects the total reflected intensity that results from the interference of these two fields. The initial phase difference between the two regions can be tuned to increase the sensitivity by over-etching the aperture.