Metal-Dielectric Waveguides for High-Efficiency Coupled Emission

We report a metal-dielectric planar structure that provides high-efficiency coupling of fluorescence at distances over 100 nm away from the metal surface. This hybrid metal-dielectric waveguide (MDW) consists of a continuous metal film coated with a dielectric layer. We observed efficient long-range coupling of rhodamine B on top of a 130 nm layer of silica, resulting in a narrow angular distribution of the emission. The high-efficiency radiation through the Ag film appears to be due to coupling of the fluorophore to an optical waveguide mode with a long propagation length and a narrow resonance. The results were consistent with simulations. These multilayer structures can be made using vapor deposition and/or spin coating, and the silica surface can be used for conjugation to biomolecules and surface-selective detection. This simple hybrid metal-dielectric structure provides new opportunities for fluorescence sensing, genomics, proteomics, and diagnostics.