Molecular fluorescence above metallic gratings

We present measurements of the fluorescence of emitters located in close proximity (d<) to metallic grating surfaces. By measuring both the spontaneous emission lifetime and angle-dependent radiation pattern of a monolayer of dye molecules as a function of their separation from planar and periodically corrugated mirrors of increasing modulation depth, we are able to examine the effect of varying the surface profile on the emission process. Both the distance dependence of the lifetime and the spatial distribution of the emitted light are significantly changed upon the introduction of a corrugation, quite apart from the appearance of the familiar Bragg-scattered bound-mode features. It is postulated that these perturbations arise from the interference of the grating scattered dipole fields with the usual upward propagating and reflected fields. In addition. the measurement of nonexponential decay transients for the deepest gratings examined provide evidence for the existence of optically dissimilar dipole positions above the grating surface.