Hypersensitivity and Applications of Cladding Modes of Optical Fibers Coated with Nanoscale Metal Layers.

Theoretical and experimental results are presented to show that the complex effective index of the modes of optical fibers coated with non-uniform metal coatings of gold, silver, copper, or palladium, with thicknesses between 0 and 20 nm, acquire a greatly enhanced sensitivity to various forms of perturbations. Thickness changes of less than 1 nm can be measured as well as the binding of record low concentrations of chemical and biochemical species.

Fiber optic Fabry-Perot sensor for surface tension analysis.

We demonstrate a new technique for analyzing surface tension of liquids. This is done upon examining the interference signals reflected from a remnant drop pending at the cleaved end of a single mode optical fiber. The resulting interference patterns are fitted to a multimirror Fabry-Perot model yielding information of the drop size. We show that the wetting process of the fiber plays an important role in drop formation; in particular, the drop size can be correlated to the surface tension of the liquid sample. The proposed configuration may render useful for liquids analysis using small sample volume.