Highly Focused Fluorescence Emission Generated by a Cylinder on Sharp Convex Gold Groove

To satisfy the requirement for analyzing low concentration analyst in microfluidic bio-detection, it is extremely crucial to enhance the sensitivity of fluorescence bio-sensing. The emission efficiency of fluorescent nanoparticles (FNPs) is low and the fluorescence emission is dispersed, which brings a challenge to the collection of emission signal and the improvement of bio-sensing sensitivity. Directional fluorescence emission enhancement is crucial to solve this problem. In this work, we propose a hybrid structure consisting of a dielectric cylinder on a sharp convex gold groove to achieve highly focused fluorescence emission in both near field and far field. Due to scattering, constructive interference, guided resonance modes (cavity modes), surface plasmon mode and photonic nanojet effect, the fluorescence excitation and far-field directional fluorescence emission are enhanced obviously. In addition, the directional fluorescence enhancement is obvious for random positions of the FNPs in the designed structures and arbitrary volume of bio-solution. Such advantages are fantastic for sensitive biochemical detection and analysis.