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Q: Quantenoptik und Photonik

Q 7: Photonik in komplexen und periodischen Strukturen I

Q 7.2: Vortrag

Montag, 13. März 2006, 11:25–11:40, H14

Talbot effect observed on microstructured surfaces — •Manuel Gonçalves, André Siegel, and Othmar Marti — University of Ulm, Dept. of Experimental Physics, Albert-Einstein-Allee 11, D-89069 Ulm, Germany

The Talbot effect, known in optics since the middle of the 19th century acquired, recently, also strong interest in atom optics. In both classical and atom optics the theoretical analysis of this effect relies on the paraxial and parabolic approximations of the Fresnel diffraction.

We show that, in some cases, this approach is inadequate. We have observed experimentally the self-imaging on two-dimensional arrays of microspheres adsorbed on flat surfaces, and on microstructured surfaces using colloidal crystals as templates. These structures can focus an incoming plane wave sharply generating very narrow light sources. We show that if the size of light sources is of the order of the wavelength, or even smaller, the conventional paraxial approximation to calculate the Talbot length, z_T, fails.

In order to explain the evolution of the light intensity with the distance to the array, we have developed an theoretical model based on the Rayleigh-Sommerfeld diffraction theory, without using the paraxial approximation. The results obtained are in good agreement with the experimental measurements. On the other hand, the diffraction patterns predicted by the classical Fresnel formalism were not observed experimentally.