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An electromagnetic metasurface refers to a kind of artificial sheet material with sub-wavelength thickness and electromagnetic properties on demand. As shown in the review article given by Capasso ''et al.'', metasurfaces could be either structured or not structured with subwavelength-scaled patterns in the horizontal dimensions. In the electromagnetic theory, metasurfaces could modulate the behaviors of electromagnetic waves through the specific boundary conditions, rather than the constitutive parameters in the three dimensional (3D) space, which is however commonly exploited in natural materials and metamaterials. Sometimes metasurfaces refer to also the two-dimensional counterparts of metamaterials. ==Definitions== The followings are several kinds of definitions made by researchers: 1, “An alternative approach that has gained increasing attention in recent years deals with one- and two-dimensional (1D and 2D) plasmonic arrays with subwavelength periodicity, also known as metasurfaces. Due to their negligible thickness compared to the wavelength of operation,metasurfaces can (near resonances of unit cell constituents) be considered as an interface of discontinuity enforcing an abrupt change in both the amplitude and phase of the impinging light”. 2, “Our results can be understood using the concept of a metasurface, a periodic array of scattering elements whose dimensions and periods are small compared with the operating wavelength”. 3, “Metasurfaces based on thin films”. A highly absorbing ultrathin film on a substrate can be also considered as a metasurface, with properties not occuring in natural materials.〔 Following this definition, the thin metallic films such as that in superlens are also early type of metasurfaces.〔 〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Electromagnetic metasurface」の詳細全文を読む スポンサード リンク
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