Band split in multiband all-dielectric left-handed metamaterials

In this paper, we propose and fabricate multiband all-dielectric left-handed metamaterials (ADMs) in the X-band microwave regime. The ADMs are fabricated by a combination of dielectric resonators in shapes of cubes and rods. The ADMs can exhibit two left-handed pass bands while the rods contact the sidewalls of the waveguide. A band split phenomenon is observed when the boundary conditions of dielectric rods change. The two pass bands can diverge into three left-handed pass bands when the rods do not contact the waveguide. By using field analysis and dielectric resonator theory, we prove that the boundary conditions have a strong influence on the resonant modes of the rod resonator, which plays key roles in left-handedness. The boundary tuned resonant modes can broaden our ways of designing new types of metamaterials.