Microwave metamaterial absorber with nλ0/2 dielectric thicknesses

Most of the metamaterial absorbers are thin planar configurations, of which the thicknesses of dielectric slabs are much smaller than 1/10 of the absorbing wavelength. On increasing the thicknesses of dielectric slabs in limited scales, the absorptions become poor. And the surface currents in metal resonators and ground planes are anti-parallel. In this paper, we theoretically demonstrate that, when thicken the dielectric slab of a conventional metamaterial absorber for nλ₀/2 (n=1, 2, ...), it can also achieve the near-unit absorption properties and the surface currents in metal resonator and ground plane are not associated any longer. Moreover, the electromagnetic wave energy can be completely absorbed by the metal resonators and the main function of ground plane is to reflect the incident EM waves back to the metal resonators. These findings can broaden the potential applications of the metamaterial absorbers in microwave and optics areas, especially in the invisible screens for large area objectives.