光束在周期结构表面的反常散射

Anomalous Scattering Of Beams By Periodic Structures

本文研究了反射光栅散射的高斯光束的场分布,证明它们与几何预示的散射场有很大区别。散射光束一般受到诸如横向位移,聚焦位移和角度偏转等空间修正,同时,光腰大小也改变。如果入射角与光栅可以传播的泄漏波相位匹配时,修正效应最大,这种情况与Wood反常现象出现有关。根据对表面阻抗呈正弦变化的光栅散射场的分析,证明这些空间修正效应是很大的。

We investigate the fields of Gaussian beams scattered by reflection gratings and show that their behavior may differ considerably from that predicted by geometrical considerations. In general, we find that those beams undergo spatial modifications which consist of a lateral displacement, a focal shift and an angular deflection; in addition, the size of the beam waist is also changed. The beam modifiations are largest if the incidence angle is phase-matched to a leaky wave that may be supported by the giating; this situation is associated with the presence of strong Wood's anomalies. By considering fields incident upon a canonic grating structure consisting of a sinusoidel reactance plane, we show that the spatial modications can be very large, so that the diffracted beams may occupy regions that are quite different from those expected