Ultra-broadband electromagnetic wave absorber based on split-ring resonators

We propose an ultra-broadband electromagnetic wave absorber by a periodic array of a four-layer split-ring resonator structure. The absorption bandwidth reaches 3386 nm, ranging from 685 to 4071 nm, with the absorptivity above 90%. Moreover, the spectrally averaged absorption is up to 94.3% in the wavelength region from 600 to 4200 nm. The ultra-broadband absorption mainly results from the plasmonic dipolar resonance, near-field coupling, and the plasmon cavity resonances by the refractory metals. The effects of different structural parameters, geometric shapes, and material properties on absorption properties are discussed in detail. In addition, the electromagnetic wave absorber exhibits excellent performance with polarization independence and incident-angle insensitive responses. The ultra-broadband electromagnetic wave absorber could show broad application prospects in thermo-photovoltaics, thermo-electrics, and infrared detection. (C) 2019 Optical Society of America