Shadow Theory of Diffraction Grating
Shadow Theory of Diffraction Grating
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衍射光栅的影子理论
DOI：
10.1587/transele.e92.c.17
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发表时间：
2008
期刊：
影响因子：
--
通讯作者：
J. Nakayama
中科院分区：
文献类型：
--
作者：
J. Nakayama
本文讨论了周期性光栅对平面波的衍射的新公式。作为一个简单的例子，讨论了由完全导电的矩形凹槽周期阵列引起的横向磁波的衍射。基于在低掠射角入射角下不发生衍射、仅发生反射且反射系数为-1的阴影假设，本文提出了散射因子这一新概念。在散射因子方面，得到了几个关于衍射振幅、衍射效率和光学定理的新公式。新发现，由于互易性，散射因子是偶函数。衍射效率是针对传播的入射波和倏逝的入射波定义的。然后，从理论上发现，当实际入射角变低掠射时，0级衍射效率变得一致并且任何其他级衍射效率消失。图中示出了散射因子和衍射效率的数值示例。
This paper deals with a new formulation for the diffraction of a plane wave by a periodic grating. As a simple example, the diffraction of a transverse magnetic wave by a perfectly conductive periodic array of rectangular grooves is discussed. On the basis of a shadow hypothesis such that no diffraction takes place and only the reflection occurs with the reflection coefficient -1 at a low grazing limit of incident angle, this paper proposes the scattering factor as a new concept. In terms of the scattering factor, several new formulas on the diffraction amplitude, the diffraction efficiency and the optical theorem are obtained. It is newly found that the scattering factor is an even function due to the reciprocity. The diffraction efficiency is defined for a propagating incident wave as well as an evanescent incident wave. Then, it is theoretically found that the 0th order diffraction efficiency becomes unity and any other order diffraction efficiencies vanish when a real angle of incidence becomes low grazing. Numerical examples of the scattering factor and diffraction efficiency are illustrated in figures.