Microstructure fibres for optical sensing in gases and liquids

A novel water-core microstructure fibre design allows nearly ideal guidance for aqueous sensing applications. The total internal reflection by a microstructured silica-air cladding provides robust confinement of light in a fluid-filled core, if the average cladding index is sufficiently below the index of water. Numerical results show dramatically improved loss and overlap of light with the sample, compared to evanescent-field fibres, indicating a direct improvement of sensor performance. A strategy for the improvement of evanescent-wave gas sensors is also discussed.