Darmstadt 2008 – wissenschaftliches Programm
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Q: Fachverband Quantenoptik und Photonik
Q 23: Photonik II
Q 23.1: Vortrag
Dienstag, 11. März 2008, 16:30–16:45, 2B/C
Limits for kinematical diffraction of visible light from three dimensional photonic crystals — •Marcel Roth1, Ullrich Pietsch1, Georg von Freymann2, and Martin Wegener2 — 1Institute of solid state physics, University of Siegen, 57072 Siegen, Germany — 2Institute of applied physics, University of Karlsruhe, 76131 Karlsruhe, Germany
For the majority of research studies with photonic crystal the existence and spectral width of a photonic band gap are of main interest. Light diffraction experiments with wavelengths in the visible and near infrared spectrum are predominantly used to verify the structural quality of the crystals.
The usage of photonic crystals as purely diffractive elements in optical detectors is a relatively new idea. Due to the three dimensional periodic structuring an incoming white beam is spatially seperated into symmetry equivalent coloured spots that can be used for object recognition.
All geometrical aspects can be understood in the framework of the von Laue equations. On the other side an analytical description for diffraction efficiencies is restricted to the case of kinematical scattering well known from the x-ray diffraction. This approximation is typically not valid for most photonic crystals because of large dielectric contrasts.
In this talk we present experimental investigation and results of numerical calculations based on Maxwell equations which show that the limit for kinematical diffraction at photonic crystals is estimated for a relative dielectric mismatch of about 5%.