Broadband Conductance Matching Effect in Conductive Metamirrors

With recent advances in materials and structures, considerable progress has been achieved in realizations of thin metamaterials designed for absorbing electromagnetic waves. The thickness of most absorbers, however, is still proportional to the working wavelength in the pursuit of perfect matching of the complex input impedance. This leads to a significant increase in the overall thickness of absorbers at low frequencies. Here, we theoretically reveal a broadband conductance matching effect in conductive metamirrors. When the conductivity‐thickness production is equal to 8 mS, the real part of the input admittance is self‐matched to the free space over a broadband frequency range. Covered with a high‐index dielectric film, this conductive metamirror is capable of achieving single‐resonance absorption across a frequency range spanning two orders of magnitude. A porous metaconductor is designed to achieve a low‐band locked metamirror, with its high‐band absorption can be flexibly tuned by the Fabry‐Perot resonances of dielectric films. This finding offers an alternative route toward ultrathin multi‐band compatible metamaterial devices.