Dresden 2009 – scientific programme

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DF: Fachverband Dielektrische Festkörper

DF 6: Poster I

DF 6.16: Poster

Tuesday, March 24, 2009, 09:30–12:30, P5

Laser Light Scattering by 3D Phase Lattices — •Björn Brüser and Ullrich Pietsch — Universität Siegen, Siegen, Deutschland

We have investigated recently developed three-dimensional phase lattices with lattice constants in the µ m - regime by means of laser-light diffraction. The samples have been manufactured by multiple beam interference into light-sensitive polymers resulting in a three-dimensional sinusoidally modulated refractive index distribution which differs by no more than Δn= 0.001 between maximum and minimum. For reasons of stability these holograms are sandwiched in between two glass-plates. Because of their 3D periodicity and the fact that the lattice parameters are in the micron range the structures can also be described as photonic crystals. The realized crystallographic structure is of hexagonal or rhombohedral (trigonal) symmetry. Due to crystalline symmetry the sampleséxposure with a coherent white beam of visible light will result in Laue spots of different colour at different incident angles. The degree of colour separation depends on the diffraction order and on the number of periodically stacked hexagonal planes within the sample, in our case ranging from 10 to 30. Experimentally, we have measured the intensity distribution of single Laue-spots in transmission geometry for different incident angles by rotating the sample. Our experimental setup, including a high resolution diffractometer, enables us to obtain extremely precise angular measurements. The diffraction curves have been recorded and compared to a theoretical model based on an x-ray kinematical scattering approach. The validity of this model arises from the fact that there is only little change in the refractive index variation.