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.

We studied the properties of GaAs oxides which were grown by local anodic oxidation (LAO) nanolithography using an atomic force microscope. We find that the LAO structures desorb under irradiation with soft x-rays (130eV). We analyzed the desorption process in detail by time-resolved photoelectron spectroscopy. We observe that even in the first stages of light exposure the LAO oxide is mainly composed of Ga2O, with a small fraction of Ga2O3 and As oxides. The As oxides are located only in the surface layers of the LAO oxide where they account for 10% of the oxide. Within 160minutes of exposure they completely desorb. Moreover, we find evidence for the presence of unoxidized GaAs embedded in the LAO oxide.

We study the fluorescence enhancement of a single emitter coupled to two spherical gold nanoparticles and discuss the differences with respect to coupling to a single one. We also show that by changing the aspect ratio of the nanoparticles we can easily tune the plasmon-mediated enhancement from the infrared to the visible range. We present the fabrication of our nanoantennae by two alternative methods, namely X-ray interference lithography followed by focused ion beam milling and electron beam lithography. The manufactured structures are characterized individually by confocal microscopy.

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