Independent dual-band absorptions with large frequency ratio and large bandwidth ratio from composite metamaterials of water pyramids over Helmholtz resonators

Abstract

We demonstrate the perfect trapping of electromagnetic fields at dual frequencies through composite metamaterials of a water pyramid cascaded meta-surface loaded with a Helmholtz resonator array. More specifically, the water pyramid cascaded meta-surface functions as an ultra-wideband absorber at the frequency range of 6.6–100 GHz with more than a 175 % relative bandwidth, while operating as a transparent screen at lower frequencies for the Helmholtz resonators. On the other hand, the Helmholtz resonator array will absorb electromagnetic fields at 100 MHz with the Q factor of 63 and the total thickness of 1/160 wavelengths, while performing as the ground for the water pyramids. The proposed design, integrating the water pyramid cascaded meta-surface with a Helmholtz resonator array for the independent dual-band absorptions with a large frequency ratio and large bandwidth ratio, should pave the way for building up more advanced energy-harvesting meta-devices.