ESM_File_Fig9 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.

本研究旨在探讨电磁波（EM）对可重构超材料圆柱阵列（即超光栅）的照射效应，以识别其在可重构亚波长表面领域的潜力。这些超圆柱体由紧密排列的薄板微结构阵列构成，在板间间距极小的极限情况下，可由半解析连续模型进行描述。在借鉴了水波中的超圆柱体分析的基础上，本研究将该方法拓展至电磁场，针对横向电场极化（纵向磁场）的情形，超圆柱体表现出各向异性散射特性；这一特性被用于研究由无限超光栅产生的光的多重散射，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研究。这些光谱揭示了诸如完美反射、传输场中的负Goos-Hänchen位移以及远场散射系数的完美对称性等异常效应。此外，超光栅还支持瑞利-布洛赫表面波，其色散依赖于圆柱体的均匀角度，随着圆柱体角度接近水平，旋转下的色散会向光线方向偏移。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体变量，而超光栅可通过旋转其组成的超圆柱体进行调节。