Ultra-thin absorber based on phase change metamaterial superlattice

In this paper, a superlattice VO₂/SiO₂ metamaterial on a lossy substrate is designed to create a near perfect absorber with tunability across the infrared spectrum. We selected VO₂ as it presents a dielectric to metal-like phase change slightly above room temperature. Additionally, the slightly lossy nature of high-temperature VO₂ presents comparable and small components (real and imaginary) of the complex refractive index across portions of the visible and infrared. Coupled with a limited conductivity substrate, VO₂ has been employed to create highly absorbing/emitting structures where the thickness of the VO₂ is ultra-thin (t <;<; λ/4n). Nevertheless, metal-like VO₂ does not possess comparable and small components of the complex refractive index across the entire infrared spectrum, which limits the universality of this ultra-thin VO₂ absorber design. Here we employ an ultra-thin superlattice of VO₂/SiO₂ to create a composite metamaterial that is readily designed for high absorbance across the infrared spectrum.