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O: Oberflächenphysik

O 29: Poster session II (Nanostructures, Magnetism, Particles and clusters, Scanning probe techniques, Time-resolved spectroscopy, Structure and dynamics, Semiconductor surfaces and interfaces, Oxides and insulators, Solid-liquid interfaces)

O 29.1: Poster

Mittwoch, 29. März 2006, 14:30–17:30, P2

Non-paraxial Talbot effect at arrays of microspheres and microstructures — •Manuel Gonçalves, André Siegel, Alexander Gigler, and Othmar Marti — Department of Exp. Physics, University of Ulm, D-89069 Ulm, Germany

The Talbot effect, known in optics since the middle of the 19th century was observed in atom optics in 1995. Since then, an increasing attention has been drawn to this effect in both classical and atom optics. One of the reasons for that is the connection between the Talbot effect and the optical coherence. However, most of the theoretical analysis has been based on the paraxial approximation of optical rays. In some cases this approach is inadequate.

We have measured the Talbot effect for two-dimensional arrays of microspheres, on flat surfaces, and for microstructured surfaces using colloidal crystals as templates. These structures can focus strongly plane waves generating very sharp light sources. We show that if the size of light sources is of the order of the wavelength, or even smaller, the conventional paraxial approach to calculate the Talbot length z_T fails.

We have developed a theoretical model based on the scalar diffraction theory to calculate the field in the Fresnel region, without using the paraxial approximation. The results obtained are in good agreement with the experimental measurements. By contrary, the simulations based on the Fresnel diffraction were not observed experimentally.