ESM_File_Fig4 from A tunable electromagnetic metagrating

We explore electromagnetic (EM) wave incidence upon gratings of reconfigurable metamaterial cylinders, which collectively act as a metagrating, to identify their potential as reconfigurable subwavelength surfaces. The metacylinders are created by a closely spaced microstructured array of thin plates that, in the limit of small inter-plate spacing, are described by a semi-analytical continuum model. We build upon metacylinder analysis in water waves, translating this to EM for TE polarization (longitudinal magnetic field) for which the metacylinders exhibit anisotropic scattering; this is exploited for the multiple scattering of light by an infinite metagrating of uniform cylinder radius and angle, for which we retrieve the far-field reflection and transmission spectra for plane-wave incidence. These spectra reveal unusual effects including perfect reflection and a negative Goos–Hänchen shift in the transmitted field, as well as perfect symmetry in the far-field scattering coefficients. The metagrating also hosts Rayleigh–Bloch surface waves whose dispersion is contingent on the uniform cylinder angle, shifting under rotation towards the light-line as the cylinder angle approaches the horizontal. For both plane-wave scattering and the calculation of the array-guided modes, the cylinder angle is the principal variable in determining the wave interaction, and the metagrating is tunable simply through rotation of the constituent metacylinders.本研究所探讨的是电磁波（EM）对可重构超材料圆柱阵列的衍射现象，该阵列协同作用形成超光栅，以评估其在可重构亚波长表面领域的潜在应用价值。超圆柱体由紧密排列的微结构薄板阵列构成，当板间间距极小时，其特性可用半解析连续模型描述。本研究在基于水波的超圆柱体分析的基础上，将其拓展至电磁波领域，针对TE极化（纵向磁场）情况下的超圆柱体各向异性散射现象进行探讨；此现象被用于通过无限超光栅对光进行多次散射，该超光栅由半径和角度均匀的圆柱体构成，我们对其平面波入射下的远场反射和透射光谱进行了求解。这些光谱揭示了包括完美反射和传输场中的负Goos-Hänchen位移在内的异常效应，以及远场散射系数的完美对称性。超光栅还支持瑞利-布洛赫表面波，其色散率依赖于均匀圆柱体的角度，随着圆柱体角度趋于水平，在旋转过程中向光线方向偏移。对于平面波散射以及阵列引导模式的计算，圆柱体角度是决定波相互作用的主要变量，而超光栅可通过旋转其组成超圆柱体进行调控。