Multifunctional High-Efficiency Transmissive/Absorptive/Reflective Metamaterial Characterized by Wideband Responses

This article presents a novel absorptive multifunctional metamaterial with switchable high-efficiency and wideband in-band response while providing stable out-of-band shielding performance. Distinct from conventional cascaded rasorber-based designs requiring resonant bands alignment between lossy/lossless arrays, an innovative filtering cavity, which could confine and manipulate the incident energy within it, is developed to achieve exceptional bandwidth and efficiency behaviors. The polarization-selection and ohmic-loss characteristics of each cavity’s spectrum-distinct array could be independently controlled, and with an appropriate biasing strategy, three distinct mechanisms of second-order filter, wideband absorption, and multireflective shielding can be obtained and switched through one structure. These functionalities are realized through four polarization-independent and three all-polarized control modes, and each state presents nearly identical performance in its corresponding mode. Therefore, high-transmittance windows with the minimum insertion loss of 0.1 dB are realized in the filter mode with the 95% fractional bandwidth of 40%. When switching to the absorption mode, the incident energies within the passband can be efficiently absorbed by the structure (the bandwidth of 95% absorption rate is 30%). In the reflection mode, the metamaterial acts as a perfect multireflector throughout the operating band. It is worth noting that, attributing to the quasi-symmetric structure, the proposed method not only independently provides the aforementioned performance under both TE and TM incidences without degrading the performance of other modes, but also enables all-polarized functions of filter, absorber, and reflector. Finally, a prototype is fabricated for measurements, and the calculated, simulated, and measured results validate the proposed design.