Enhancement of fluorescence-based sensing using microstructured optical fibres.

We develop a generic model of excitation and fluorescence recapturing within filled microstructured optical fibres (MOFs) with arbitrary structure and demonstrate that the light-matter overlap alone does not determine the optimal fibre choice. Fibre designs with sub-wavelength features and high-index glasses exhibit localised regions of high intensity, and we show that these regions can lead to approximately two orders of magnitude enhancement of fluorescence recapturing. Here we show how this regime can be exploited for sensing and demonstrate experimentally in-fibre excitation and fluorescence recapturing within a filled, solid-core MOF.