Effective dielectric constant of two-dimensional photonic crystals in optical bands |
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Authors: | Yong Zeng Ying Fu Wei Lu |
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Institution: | a National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Science, Shanghai 200083, China b Department of Theoretical Chemistry, School of Biotechnology, Royal Institute of Technology, AlbaNova, S-106 91 Stockholm, Sweden |
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Abstract: | By using the Fourier expansion method, we have developed an approach to calculate the effective dielectric index of a two-dimensional photonic crystal. The approach is very general: it can take into account various Bravais lattice structure as well as arbitrary spatial variation of the dielectric index. It has been found that near a nondegenerate frequency ωn(Γ) at Γ point, the transverse magnetic (TM) mode is ordinary, as it is independent of the propagation direction, whereas in general the transverse electric (TE) mode depends on the propagation direction, it is extraordinary. Therefore, a two-dimensional photonic crystal can always be described by an effective dielectric index for TM mode near the nondegenerate frequency ωn(Γ). However, the TE mode is much more complicated unless the lattice structure is highly symmetric. Moreover, a two-dimensional square photonic crystal has been identified as an effective birefringent crystal having two negative refractive indexes from the perspective of Snell's law. |
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Keywords: | 42 70 Qs 41 20 Jb 42 25 Lc |
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