Tunable broad-band perfect absorber by exciting of local surface plasma modes resonances at terahertz frequency

Abstract

A broadband metamaterial absorber is proposed and measured in this paper, which consisted of two patterned square metal patches and a same-size patterned square dielectric patch alternately stacking on a bottom dielectric-metallic ground plane. The measured metamaterial absorber gives shows a broadband absorption performance, while the single layer structure with the same structural parameters only achieves a narrow absorption peak. The full width at half maximum (FWHM) is 2.2 THz, which is higher than that of the single-layer structure. Electric field intensity distribution calculation results display that the resonance and vertical coupling of local surface plasma (LSP) modes between two patterned square metal patches results in the absorption band. Effective parameter extraction results display that the impedance matching condition is reached in the absorption band. Measured results indicate that the absorption band is shifted the lower frequency with the side length w of square metal plates increasing, while the absorption band is shifted the higher frequency with the dielectric layer thickness h1 and h2 increasing. An equivalent LC resonance current model is established to explain the effect of geometric parameters on the absorption performance. Moreover, the measured absorber exhibits the property of broadband absorption at the incident angle of 60°.