ESM_File_Fig5 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）照射于可重构超材料圆柱阵列，该阵列整体构成超晶格，以揭示其作为可重构亚波长表面的潜力。这些超圆柱通过紧密排列的薄板微结构阵列形成，当板间间距极小时，可由半解析连续模型进行描述。我们基于水波中的超圆柱分析，将此方法应用于电磁波，针对TE极化（纵向磁场），超圆柱表现出各向异性散射；这一特性被用于研究无限超晶格对光的多次散射，该超晶格由半径和角度均匀的圆柱阵列构成，我们通过平面波入射获取了其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。此外，超晶格还支持瑞利-博洛赫表面波，其色散依赖于圆柱的均匀角度，当圆柱角度接近水平时，随着旋转逐渐趋向光线。对于平面波散射和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，而超晶格可通过旋转其构成的超圆柱进行调节。