Publication: A simple scheme for rapid three-dimensional orientation determination of the emission dipole of single molecules

J. Hohlbein and C.G. Hübner, Applied Physics Letters, 86, 121104, 2005, [link]

One of the unique features of single molecule absorption and emission is their anisotropy due to the well-defined transition dipole(s) for both processes allowing the determination of the molecule’s orientation. While polarization-resolved techniques are usually capable of detecting only a projection of the transition dipole, several methods have been proposed in order to determine the full three-dimensional orientation. Here, we report on a detection scheme that allows for a shot-noise limited determination of the emission dipole orientation utilizing an annular mirror, a polarizing beam splitter in conjunction with three detectors in a scanning confocal optical microscope.

Publication: Recurrence and photon statistics in fluorescence fluctuation spectroscopyical Review

G. Zumofen, J. Hohlbein, and C.G. Hübner, Physical Review Letters, 93, 260601, 2004, [link]

We report on fluorescence fluctuations of nanoparticles diffusing through a laser focus. Subject to an intensity threshold the fluorescence signal is transformed into time traces of on and off periods. The distribution functions of the experimental on and off times follow power laws t^-alpha over several orders of magnitude with exponents alpha equal 1.5-2. At long times the distribution functions cross over to exponential decays. For the interpretation of the experimental data a diffusion-reaction equation is proposed which covers both, the diffusion controlled recurrence and the photon statistics as the relevant processes.

Publication: In-situ optical characterisation of porous alumina

J. Hohlbein, U. Rehn, and R. B. Wehrspohn, Physica Status Solidi (a), 204, 803, 2004, [link]

We present a new method to characterize in-situ the optical thickness of porous alumina films by the use of photoluminescence-induced Fabry-Perot-interferences. Additionally we show, that the use of different electrolytes yields different photoluminescence pattern. A second experiment allows to determine the degree of filling of the pores by a liquid which is of importance when using the pores as templates.