ESM_File_Codes 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.

本项研究深入探讨电磁波（EM）照射至可重构超材料圆柱体阵列（集体作用构成超光栅）的情形，旨在揭示其作为可重构亚波长表面的潜在价值。这些超圆柱体由紧密排列的薄板微结构阵列构成，在板间间距极小的极限条件下，可用半解析连续模型进行描述。我们基于水波中的超圆柱体分析，将其应用于电磁波领域，针对TE极化（纵向磁场）情形，超圆柱体表现出各向异性散射；此特性被用于通过无限超光栅对光的多次散射，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条件下的远场反射和透射光谱进行了研究。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。超光栅还支持Rayleigh-Bloch表面波，其色散依赖于均匀圆柱体的角度，随着圆柱体角度趋近于水平，在旋转过程中向光线路径偏移。对于平面波散射和阵列引导模式的计算，圆柱体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其的超圆柱体进行调节。