Beam shaping the evanescent field for distributed fluorescence-based optical fibre sensing

High resolution distributed chemical and biological sensing will enable new discoveries in biological and biomedical applications. Single-point chemical and biological optical fibre sensors often utilise fluorescence-based approaches, which allows high sensitivity and specificity. Achieving distributed sensing at a biologically relevant resolution (< cm) is hindered by the incoherent nature of fluorescence emission. Wavefront shaping of the excitation light in a multimode exposed-core microstructured optical fibre is a promising technique to enhance spatial selectivity by controlling the fluorescence excitation region. This paper gives proof-of-concept numerical and experimental results where we enhance the evanescent field at selected locations along the fibre, and discuss the potential for enhancement by using multi-photon fluorescence.