Plasma absorption levelling by phase coherence in meta-surface stacked structure

Abstract: In this paper, we propose a MIM (metallic metasurface-insulator-metal) stacked structure to realize perfect absorption in mid- and far- infrared bandwidth. A large number of metallic composite metallic units placed on a uniform layer of insulator Ge which is deposited on a uniform metallic Ti surface. Each of units consists of four right-angled triangular cubes in middle of four sides of a square. Three resonant absorption peaks can be discrete or levelling dependent to thickness of cubes. Once metallic cubes are thinner than its skin depth, an effective ultra-broadband absorber is realizable with average absorption over 90% percent ranging from 8-14{\mu}m. We build a four-level cavity-dipole interacting model to explain phenomena of plasma absorption levelling. This is created by strong phase coherence from meta-surface since three hybrid modes are coupled by common cavity photons in arrays of micro-cavities between top and below metallic layers. The structure is polarization-selective to infrared light. It has great potential in infrared detection and imaging.