ESM_File_Fig8 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.

本项研究旨在探讨电磁波（EM）波束照射至可重构超材料圆柱阵列构成的元光栅上，以识别其作为可重构亚波长表面的潜在应用。这些超材料圆柱通过紧密排列的薄板微结构阵列形成，在板间间距极小的极限情况下，可由半解析连续模型来描述。本研究基于水波中的超圆柱分析，将其转化为电磁波领域，针对TE极化（纵向磁场）情况下的超圆柱各向异性散射现象。这一特性被用于由半径和角度均匀的无限元光栅对光的多重散射中，我们成功获取了平面波入射下的远场反射和透射光谱。这些光谱揭示了诸如完美反射和传输场中的负Goos-Hänchen位移等异常效应，以及远场散射系数的完美对称性。元光栅还支持瑞利-布洛赫表面波，其色散依赖于均匀圆柱的角度，随着圆柱角度接近水平，在旋转过程中向光轴方向偏移。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要变量，而元光栅可通过旋转其组成超圆柱进行调谐。