Photonic crystals are regular arrays of dielectric materials with different refractive indices or discrete metallic objects. They are classified mainly into three categories that is one-dimensional, two-dimensional, and three-dimensional crystals according to the dimensionality of the stack. Since they are easy to fabricate and have some special properties, they not only have widely been used as frequency selective or polarization selective devices in microwaves and optical waves, but also are expected for new application. A typical structure of two-dimensional photonic crystals is formed by stacking periodic arrays constituted with infinitely long cylindrical objects. In the layered structure, the multiple interaction of space-harmonics scattered from each of array layers pronounces the frequency response and the photonic bandgaps are formed in which any electromagnetic wave propagation is forbidden within a fairly large frequency range.
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