Highly efficient fluorescence sensing using microstructured optical fibres: general model and experiment

Abstract

A general model of excitation and fluorescence recapturing by the forward and backward modes of filled microstructured optical fibres (MOFs) is developed for fluorecence-based fibre optic sensors. It is demonstrated that the light-matter overlap alone does not determine the optimal fibre choice for maximum sensing efficiency. 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. We demonstrate higher efficiency of fluorescence recapturing into backward modes in comparison with that of forward modes. We present experimental results for both backward and forward flourescence recapturing and demostrate a good qualitative agreement between the numerical model and experimental results.