Use of a scanning near-field optical microscope architecture to study fluorescence and energy transfer near a metal

Fluorescence intensity depends strongly on the distance between the emitting molecule and a metallic interface. We show that a scanning near-field optical microscope (SNOM) is a simple and versatile tool for studying such an effect. The fluorescent molecules are embedded in a layer upon a silica substrate, and metal is coated on the SNOM tip. We present variations of fluorescence intensity versus tip-sample distance from 800 to ~80 nm . A simple model is used to explain the experimental results. The proposed setup could be used to study nonradiative transfer at a nanometric scale. It could also yield to a new type of optical near-field profiler that uses fluorescent signal.