ESM_File_Fig10 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.

本研究深入探讨了电磁波（EM）对可重构超材料圆柱阵列（作为整体超栅格）的入射现象，以评估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，在板间距离极小的极限情况下，可由半解析连续模型描述。我们基于水波中的超圆柱体分析，将其转化为电磁波领域，针对TE极化（纵向磁场）进行了研究，此时超圆柱体表现出各向异性散射；这一特性被用于通过无限超栅格对光的多次散射，该栅格由均匀圆柱半径和角度构成，我们成功获取了平面波入射下的远场反射和透射光谱。这些光谱揭示了独特的效应，包括完美的反射以及传输场中的负Goos-Hänchen位移，以及远场散射系数的完美对称性。超栅格还承载着瑞利-布洛赫表面波，其色散依赖于均匀圆柱的角度，当圆柱角度趋近于水平时，随着旋转而向光线方向偏移。在平面波散射以及阵列引导模式的计算中，圆柱角度是决定波相互作用的主要变量，而超栅格可通过旋转其组成的超圆柱体进行调节。