We demonstrate a near-field tomography method for investigating the coupling between a nanoscopic probe and a fluorescent sample. By correlating the arrival of single fluorescence photons with the lateral and vertical position of an oscillating tip, a complete three-dimensional analysis of the near-field coupling is achieved. The technique is used to reveal a number of interesting three-dimensional near-field features and to improve image contrast in tip-enhanced fluorescence microscopy. Light-matter interactions are of fundamental importance for a host of nanoscale phenomena and emerging nanotechnology applications. Such interactions can be altered by proximate surfaces, particularly near nanostructures with sharp facets such as lightning rods, 1,2 optical antennae, 3-5 and roughened surfaces. 6-8 For example, in surface-enhanced Raman spectroscopy (SERS) the optical scattering cross section is enhanced for molecules near “hot spots ” on a nanostructured surface, leading to an increase in the molecular detection efficiency. 9 The enhanced near-field at the en
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