读ㄅ下猪来打yee打字赚P币豪惹 The notion that the electromagnetic response of a material can be engineered via periodic variations in structure and composition has been extensively investigated. A well-known example are photonic crystals, dielectric materials with a periodic modulation of their real refractive index, achieved via the inclusion of scattering elements such as holes of different dielectric constant into the embedding host. This way, the dispersion relation for the EM waves propagating through the artificial crystal can be engineered and band gaps in frequency space established that inhibit propagation. In photonic crystals, both of the size and the periodicity of the index modulations are of the order of λin the material. A possibility of designing artificial materials with a controll photonic response are metamaterials. In contrast to photonoc crystals, in this case both the size and periodicity of the scattering elements are signficantly smaller than λ Therefore, they can be viewed as microscopic building blocks of an artificial material. The corrugated perfectly-conducting surfaces are an example of a metameterial . The metameterial concept of creating composites with desired EM properties has already enabled new possibilities for the control of EM radiation in the THz and microwave region of the spectrum. Another prominent example of a metameterial sustaining low-freq plasmons is a regular 3D latice of metal wires with micron-size diameter. 耶我不打渍了 快热～ lalalalalalalala -- --

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