All-dielectric ultra-broadband metamaterial absorber based on imidazole ionic liquids

We propose an all-dielectric hollow annular groove ultra-broadband metamaterial absorber (A-D ILMMA) based on imidazole ionic liquids, which is freed of metallic substrate and can offer an extremely wide bandwidth of electromagnetic absorption and prominent wide polarization angle range. When the ionic liquid 1-ethyl-3-methylimidazolium Tetrafluoroborate ([EMIM][BF 4 ]) with a high conductivity and dielectric loss factor is arranged into the hollow annular groove unit cells with a 6 mm total thickness, nearly perfect impedance matching can be achieved in a wide frequency range. Research results show that the simulated absorptivity is over 90% in 13.9–50 GHz with the relative bandwidth of 113%, and the corresponding microwave experiment is performed to support the results of the simulation. Moreover, the A-D ILMMA can work efficiently at arbitrary polarization angles from 0° to 90° and wide incident angles from 0° to 60°.