Steering Fluorescence Emission with Metal-Dielectric-Metal Structures of Au, Ag and Al.

Directional control over fluorescence emission is important for improving the sensitivity of fluorescence based techniques. In recent years, plasmonic and photonic structures have shown great promise in shaping the spectral and spatial distribution of fluorescence, which otherwise is typically isotropic in nature and independent of the observation direction. In this work we have explored the potential of metal-dielectric-metal (MDM) structures composed of Au, Ag or Al in steering the fluorescence emission from various probes emitting in the NIR, Visible or UV/blue region. We show that depending on the optical properties of the metal and the thickness of the dielectric layer, the emission from randomly oriented fluorophores embedded within the MDM substrate is transformed into beaming emission normal to the substrate. Agreement of the observed angular emission patterns with reflectivity calculations reveals that the directional emission is due to the coupling of the fluorescence with the electromagnetic modes supported by the MDM structure.