ESM_File_Fig6 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.

本研究深入探讨电磁波（EM）照射至可重构超材料圆柱阵列（集成为超光栅）的现象，旨在揭示其作为可重构亚波长表面的潜力。这些超圆柱体由紧密排列的薄板微结构阵列构成，当板间间距极小时，其特性可通过半解析连续模型进行描述。本研究基于水波中的超圆柱体分析，并将其扩展至电磁波领域，特别是对于TE极化（纵向磁场）情况下的超圆柱体各向异性散射现象。利用此特性，我们研究了由均匀圆柱半径和角度组成的无限超光栅对光的多重散射，并获取了平面波入射下的远场反射和透射光谱。这些光谱揭示了诸如完美反射和透射场中的负Goos-Hänchen位移等异常效应，以及远场散射系数的完美对称性。此外，超光栅还支持瑞利-布洛赫表面波，其色散依赖于均匀圆柱的角度，随着圆柱角度趋近于水平，在旋转过程中向光线路径偏移。对于平面波散射以及阵列引导模式的计算，圆柱角度是决定波相互作用的主体变量，而超光栅可通过旋转组成超圆柱体进行调谐。