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

Abstract

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.