基于双粒子耦合的单层介质柱阵列对电磁波的调控

基于Mie散射理论和多重散射理论探讨了亚波长介质柱阵列对电磁波的调控. 研究结果表明: 当在全反射的单层介质柱阵列中引入一个空位缺陷时会产生12%的透射; 如果在入射一侧再引入一合适的介质柱时, 其透射率可增加至36%, 为空位缺陷时的3倍; 当在出射一侧对称位置处引入另一完全相同的介质柱时, 可以调制透射电磁波的模式, 虽然总的透射率没有增加,但向前散射的电磁波能量明显增强. 采用这种双粒子耦合体系, 在金属柱的表面等离激元共振频率附近也可以实现类似的效果. 这些体系结构简单、易于在实验上实现, 这对于太赫兹甚至光频段的光子集成线路中的元件设计和光束调控很有意义.

Rectifying electromagnetic waves by a single-layer dielectric particle array based on dual-particle coupling

Metamaterials, composed of subwavelength building blocks with artificial electric/magnetic response, have attracted the intensive interest due to the unprecedented controllability of electromagnetic (EM) waves and the potential applications. Nonetheless, the resonance of the metallic building block induces a strong loss, severely limiting the performance. Dielectric particle based subwavelength structures provide an alternative choice for the manipulation of EM waves, meanwhile, circumventing the loss problem inevitable for metallic metamaterials, in particular, in optical regime. It is shown that this kind of metamaterial can be used to guide the surface wave with the dielectric particle chain, which is similar to the surface plasmon mediated wave guiding. The structure is also shown to be capable of implementing negative refraction with negligible loss theoretically and experimentally. In addition, the single-layer dielectric rod array can be used to achieve omnidirectional total reflection at subwavelength scale. To further extend the functionality of dielectric based metamaterials and make them more appropriate for integrated optics, a variety of experimentally feasible configurations should be designed. In this work, based on the Mie scattering theory and the multiple scattering theory, we investigate the manipulation of EM waves through a single-layer subwavelength dielectric rod array (SDRA) and particle coupled system. Our results show that by removing the central dielectric rod in the SDRA and at the beam focus, like a vacancy defect, a normal incident transverse electric polarized Gaussian beam is weakly transmitted with an efficiency of less than 12 percent. By further introducing a dielectric rod with optimized parameters on the incident side of the vacancy defect, an enhanced transmitted EM wave with an efficiency of 36 percent is exhibited, nearly triple that with a solely vacancy defect. By adding another identical dielectric rod symmetrically on the outgoing side of the vacancy defect, the transmitted EM field pattern can be clearly tailored due to the dual-particle coupling so that the forward scattering is intensified, similar to the beaming effect, although the total transmittance is not further improved. Interestingly, by use of dual-particle system composed of metallic rods a similar effect can be realized as well near the surface plasmon resonance, adding flexibility to design. It should be pointed out that one-way beam propagation can be possibly achieved by constructing an asymmetric dual-particle coupling system. More importantly, the proposed systems are simple and experimentally realizable, which makes them favorable for the on-chip beam steering, offering a possibility to improve the optical element design of the integration photonic circuit in the terahertz and optical range.