All-dielectric metamaterials: double negative behavior and bandwidth-loss improvement

In this paper, realization of double-negative (DNG) metamaterials utilizing only-dielectric spherical particles, arranged periodically inside a host medium, is investigated. It is demonstrated that the dielectric particles can successfully offer both electric and magnetic dipole moments at certain frequency ranges. The plots of near-field patterns clearly illustrate this interesting phenomenon. The possibility to realize negative electric permittivity and negative magnetic permeability as a result of the resonance of TM₀₁₁ and TE₀₁₁ modes are addressed. Increasing the couplings among the spheres by bringing them close to each other will result in a larger bandwidth for each of the modes that by properly selecting the permittivities of spheres, wider DNG region can be achieved. Also, the DNG performance of an array of dielectric spherical particles producing magnetic dipole moments located periodically inside a host plasmonic material (negative permittivity) is investigated. The advantageous and challenges of the proposed designs are highlighted. In compared to the conventional designs based on metallic inclusions, all-dielectric metamaterials are free of conduction loss, and in addition they provide a wider material bandwidth. Further, all-dielectric metamaterials are more feasible for fabrication in both RF and optics. A full wave analysis based on finite difference time domain (FDTD) technique is applied to comprehensively provide a physical insight of the complex periodic structure.