Berlin 2005 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 58: Poster IIb
HL 58.30: Poster
Dienstag, 8. März 2005, 16:30–19:00, Poster TU F
Focusing microwaves with a concave lens based on a 2D photonic crystal — •E. Foca1, S. Frey1, F. Daschner1, V.V. Sergentu2, J. Carstensen1, R. Knöchel1, I.M. Tiginyanu2 und H. Föll1 — 1Faculty of Engineering, Christian-Albrechts-University, Kiel, Germany — 2LLDSP, Technical University of Moldova, Chisinau, Moldova
Photonic crystals (PC) can be considered as optically homogenous materials for the long wave length limit, thus they can be ascribed an effective electric permittivity, and an effective refractive index. However, it is more complicated when the radiation wavelength is comparable with the PC irregularities. Even in this regime there remain frequency regions where the PC can be attributed an effective refractive index.
We present a new method to find the effective refractive index of a PC in non-trivial regimes, especially for the case of 0 < neff < 1. We prove the correctness of our calculations by designing and measuring a concave lens with a 0 < neff < 1 in the microwave regime. For such a case the lens focuses the radiation and we measured that this is indeed the case. We show a good correlation between the theoretical predictions and measured data and a good focusing quality of the lens. We estimate the focusing power of the lens in terms of the transmission coefficient that reaches values as high as 40 for frequencies close to 7.5 GHz, which is extremely good since nearly no other tool for focussing of microwaves exists.