Synthetical dispersion engineering in plasmonic metamaterial absorber for broadband absorption enhancement

In this paper, a comprehensive scheme of plasmonic metamaterial absorber (PMA) is proposed which develops the non-planar plasmonic structure (PS) as a covering on resistive MA to improve k-vector-matching absorption in a wider frequency band. Owing to the synthetical dispersion engineering of spoof surface plasmon polariton, our investigation shows that the PS introduced here can not only directly achieve broadband absorption at high frequencies, but also indirectly improve the k-vector-matching absorption originated from the ground resistive metamaterial absorber (MA) at the lower frequencies. With the incorporation of two absorbing mechanisms, simulation and experimental measurement demonstrate that the proposed PMA can achieve ultra-wideband absorption with the efficiency more than 90% in the frequency band of 5.3–28.4 GHz, which has an enhancement in figure of merit compared to the former plasmonic absorbing structure. Our strategy provides an efficient and flexible design capable of broadband absorption enhancement with simultaneously polarization insensitivity, lightweight and easy fabrication, and we expect a wide range of applications to emerge from this general concept. (paper)