Berlin 2005 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

O: Oberflächenphysik

O 19: Nanostrukturen II

O 19.4: Vortrag

Samstag, 5. März 2005, 11:30–11:45, TU EB420

Talbot effect on 2D colloidal crystals — •Manuel Gonçalves and Othmar Marti — University of Ulm - Dept. of Experimental Physics, Albert-Einstein-Allee 11, D-89069 Ulm, Germany

The Talbot effect occurs when a two-dimensional periodic structure is illuminated by a planar wavefront. The standard theoretical explanation of this effect is based on Fresnel diffraction and on the paraxial approximation. The assumptions used for the Fresnel diffraction and the paraxial approximation do not apply for structures with lattice constants comparable to the wavelength. Colloidal crystals of spheres with a diameter of few micrometers have been produced. The 2D crystals, under planar illumination of laser light, produce self-images. The distance between the crystal and the self-image depends on the symmetry of the lattice, on the wavelength and on the lattice constant. The experimental results have been compared with simulations based on the diffraction at an array of small apertures, using Rayleigh-Sommerfeld diffraction integrals without any approximations. The experimental data shows that colloidal crystals can be used as Talbot illuminators for distances of several tenths of µm.