Modifcation of single molecule fluorescence close to a nanostructure: radiation pattern, spontaneous emission and quenching

The coupling of nanostructures with emitters opens ways for the realization of man-made subwavelength light emitting elements. In this article, we investigate the modification of fluorescence when an emitter is placed close to a nanostructure. In order to control the wealth of parameters that contribute to this process, we have combined scanning probe technology with single molecule microscopy and spectroscopy. We discuss the enhancement and reduction of molecular excitation and emission rates in the presence of a dielectric or metallic nanoparticle and emphasize the role of plasmon resonances in the latter. Furthermore, we examine the spectral and angular emission characteristics of the molecule-particle system. Our experimental findings are in excellent semi-quantitative agreement with the outcome of theoretical calculations. We express our results in the framework of optical nanoantennae and propose arrangements that could lead to the modification of spontaneous emission by more than 1000 times.