Regensburg 2007 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 15: Methods: Scanning Probe Techniques II

O 15.10: Vortrag

Montag, 26. März 2007, 16:30–16:45, H41

Optimum Excitation Conditions for SNOM-based Particle-enhanced Fluorescence Microscopy — •Thomas Härtling, Phillip Reichenbach, Marc-Tobias Wenzel, Phillip Olk, and Lukas Eng — Institut für Angewandte Photophysik, TU Dresden

Tip-enhanced microscopy, carried out for example by using a scattering near-field optical microscope (s-SNOM), is a powerful tool for nano-optical investigations. In this context, the manipulation of the fluorescent behavior of molecules with the help of single metal nanoparticles attached to the apex of a dielectric SNOM tip has been followed in the last years. This technique not only offers the advantages of high signal intensities confined to small spatial volumes. It equally provides deeper insight into processes involved in fluorescence emission stemming from molecular dipole transitions in the vicinity of metallic structures. It is known that the distance between the emitting molecular dipole and the metallic nanoparticle in such a configuration plays a key role in the competition between radiative and non-radiative decay processes of the excited dipolar state. Consequently, the fluorescence signal is strongly distance-dependent. We will discuss this dependence quantitatively both in theory and experiment taking into account parameters such as the excitation and emission wavelength of the dipole, the resonance wavelength of the particle, and the effect of the dielectric constant of the surrounding medium. Consequences concerning the optimum excitation conditions for particle-enhanced fluorescence microscopy are lined out.