Surface imaging in near-field optical microscopy by using the fluorescencedecay rate: a theoretical study

In this paper, we study the fluorescence decay rate of a molecule above a c orrugated interface, and particularly the variations of the decay rate as a function of the lateral position of the molecule, As a first step, one has to determine the field diffracted by a corrugated interface when the incid ent field is the field emitted by a dipole. For this purpose, we have used a perturbative Rayleigh method, and we show that the decay rate variations can be connected to the surface profile via a transfer function. Some numer ical calculations of this transfer function and of decay rate variation ima ges are presented for dielectric and metallic samples. The visibility of th e theoretical images is up to 20% and, moreover, resolution of the images i s good enough to use the fluorescence lifetime of molecules as signal in a life-time scanning near-field optical microscope. The technical problems ar e discussed briefly.