High-Performance and Ultra-Broadband Metamaterial Absorber Based on Mixed Absorption Mechanisms

Perfect absorbers are highly desirable in many military applications, such as radar cross section (RCS) reduction, cloaking devices, and also sensor detectors; however, most approaches (such as wedge and pyramidal absorbers, multi-resonant absorbers) intrinsically suffer from very large size at low-frequency domain, limited bandwidth, as well as low absorption ratio issues. In this paper, we solve these issues via combining the Huygens metasurface and three-layers slab impedance metasurface, with the former satisfying the novel impedance matching theory and the latter exhibiting multi-resonant property and optimized conductivities, which achieve high-efficiency absorption at lower frequency range (1-3 GHz) and higher frequency region (3-18 GHz), respectively. To demonstrate our concept, we design/fabricate a realistic metasurface absorber working in the microwave region, and perform experiments to demonstrate that it can achieve an ultra-broadband (1-18 GHz) performance with absorption rate better than 75%. The numerical simulations are in good agreements with experiments, indicating that the absorption efficiency can be further pushed to 92% within the whole working band by optimizing our designs. More importantly, our device is insensitive for different polarizations and oblique incidences. Our findings can stimulate the realizations of ultra-broadband meta-devices, particularly can enhance the cloaking technology relying on high-efficiency absorption.