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In recent years, with the research of metamaterial structure absorbers and the concept of plasma perfect absorber, the perfect absorbers have developed from single-band absorption to multi-band absorption, broadband absorption, and narrow-band absorption. At present, in order to achieve a wider band, great efforts have been made to develop absorbers using multi-layer structures and nanostructured designs. However, the preparation and processing process such as Electron Beam lithography, Interference Lithography, Nanoimprint Lithography, etc., are too complicated and manufacturing costs are high, resulting in the difficulty of large-area preparation. It will seriously limit the practical application of broadband perfect absorber. In addition, multi-band perfect absorbers in the ultraviolet, visible and near-infrared regions are rare and suffer from a lack of bandwidth, while the application of broadband perfect absorbers in solar cells, cloaking technology, detection and sensing has become an urgent problem. Therefore, the design and implementation of broadband perfect absorbers that can be manufactured in a simple way for mass production has become a hot topic of research. Based on the advanced theory of artificial metamaterials and the principle of impedance matching, a MIM structured broadband perfect absorber based on an array of nanospheres has been designed. The absorber consists of an array of nanospheres with a metal-medium-metal structure, which enables ultra-broadband perfect absorption. The metal materials of the absorber are platinum (Pt) and gold (Au), the media material is aluminum oxide (Al2O3). The absorption spectrum and electromagnetic field energy distribution of the absorber, as well as the influence of the incidence angle and cell structure size on the absorption performance, were studied and analyzed by COMSOL Multiphysics. Numerical calculations show that the absorber has an average absorption of more than 95% in the visible-near infrared range (400-1400nm). The broadband absorption is achieved by a combination of modes, mainly surface plasmon and Fabry-Perot resonance. This absorber can replace the micro and nano processing process with self-assembly technology, which can achieve low cost, high efficiency, broad bandwidth and large area fabrication.
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