Suppression of Bulk Fluorescence Noise by Combining Waveguide-Based Near-Field Excitation and Collection

Abstract

A high surface to bulk fluorescence ratio is very useful in bioimaging, sensing, sequencing, and physical chemistry characterization. We used the evanescent field of a photonic waveguide for highly localized excitation and collection of molecular fluorescence. As both near-field excitation and collection are strongly distance dependent, we were able to increase the surface to bulk fluorescence ratio significantly. We have also experimentally investigated the combined excitation and collection efficiency as a function of the position of the molecule in the near field. Finally, we formulated and experimentally verified a general condition for the waveguide–molecule interaction length for maximum optical efficiency of the device.