The effect of metal coating in near-field fluorescence imaging

Abstract

The effect of a thin metal coating in near-field fluorescence imaging is studied by using a model based on the plane wave decomposition, that takes into account the dynamic nature of the molecule's electronic structure, namely the modification of the fluorescence lifetime due to the near-field environment (the metal layer and the probe's presence). The electromagnetic wave crossing the metal layer generates a plasmon excitation, the effect of which is the more important when the molecules, considered as dipoles, are polarized perpendicularly to the surface and when they are in a saturated excitation state. The consequence of the plasmon excitation is a decrease in fluorescence lifetime and, for the case of molecules polarized perpendicularly to the surface, a decrease in lateral resolution. When the molecules are polarized parallel to the surface, plasmon excitation is weaker and its effect on the resolution seems to be beneficial. The interaction with the probe is also studied; its effect on imaging of molecules is weak in the presence of the metal coating.