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Frank Cichos

Publications and source records attributed to Frank Cichos.

2 recordsLinked to original sources
PubMed2006

Imaging single quantum dots in three-dimensional photonic crystals.

Performing fluorescence wide-field microscopy we have imaged single semiconductor quantum dots deep inside a 3-dimensional photonic crystal prepared from colloidal polymer beads. Exploring the emission diffraction patterns in defocused images of quantum dots we demonstrate that the direction-dependent photonic stop band imprints an anisotropy to the angular emission of a single quantum dot. Hence a single, quasi-point-like emitter is manipulated to radiate its photons only to certain well-defined directions by means of the anisotropic light propagation in photonic crystals. The experiments thus provide new routes to evaluate local, frequency selective optical properties in 3-dimensional photonic crystals employing single emitters.

Journal Article↗
PubMed2006

A modified surface forces apparatus for single molecule tracking.

To unravel molecular motion within confined liquids, we have combined a surface forces apparatus (SFA) with a highly sensitive fluorescence microscope. Details of our setup including important modifactions to enable the tracking of single dye molecules within nanometer thin confined liquid films are presented. The mechanical and optical performance of our setup is discussed in detail. For a load of 20 mN we observed a circular-shaped contact region (d approximately 300 microm), which results in a confining pressure of about 280 kPa. First experiments on liquid films of tetrakis(2-ethylhexoxy)silane (TEHOS) doped with rhodamine B demonstrated the ability to track single dye molecules within the confining gap of a SFA. The mean diffusion constant was independent of the liquid film thickness of approximately 3x10(-8) cm2/s and thus 10 times smaller than the diffusion constant of rhodamine B in bulk TEHOS. This points to the existence of a thin interface layer with slower molecular dynamics and an attractive potential parallel to the solid surface trapping molecules in this interface region.

Journal Article↗