Spatially resolved plasmonic sensing at the tip of a multimode fiber

The ability to fabricate plasmonic structures on the distal facet of an optical fiber has led to a diverse range of minimally invasive sensors. However these applications have been hindered by the inherent turbidity of the fiber and complex transmission properties of the nanostructures. We propose to use a wavefront shaping technique to pre-shape light prior to transmission through the nanostructed fiber to control the coupling between the guided modes of the fiber and the plasmonic nanostructures. We show that the sensing resolution of a plasmonic fiber optic can achieve a sub-cellular spatial resolution in biological applications. In this work, a broad range of plasmonic structures are explored as candidates for spatially resolved plasmonic sensing including periodic nanostructures for extraordinary optical transmission and sub-diffraction beam formation as well as nanoislands fabricated by a solid-state dewetting procedure for surface enhanced Raman spectroscopy.