Research on multi-resonance mechanism to achieve ultra-wideband high absorption of a metamaterial absorber in the UV to MIR range

Wideband metamaterial perfect absorbers have been extensively researched due to their excellent properties. A four-layer ultra-broadband metamaterial perfect absorber engraved with a square cavity is proposed. A clever combination of grating and square cavity allows the absorber to manifests an overall absorption of over 92 % and an average absorption rate of 97.27 % within the operational band from 280 to 5400 nm. Through analysis, it can be concluded that the coupling effects of Rayleigh anomaly (RA), magnetic resonance (MR), cavity resonance (CR), propagating surface plasmon resonance (PSPR) and local surface plasmon resonance (LSPR) result in perfect absorption. The absorber is insensitive to polarization and large angle incidence. It is worth mentioning that the average absorption rate of our structure reaches 93.32 % at a large incidence angle of 60° in TE mode, which is much higher than that of other absorbers. At 1000 K, the total photothermal conversion efficiency of our absorber is still above 90 %. The designed structure has the following advantages: high absorption, ultra-wide bandwidth, high tolerance to fabrication errors and insensitivity to large angle incidence. Thus, the absorber can be used in the solar energy harvesting and perfect stealth. Additionally, it also can be served as a reference in thermophotovoltaics, thermal imaging and infrared detection.