Visible-infrared (0.4–20 μm) ultra-broadband absorber based on cascade film stacks

In this paper, we present a glass-based double-side cascade film stack structure for visible-infrared ultrabroadband absorption. The proposed structure demonstrates an average absorption as high as ∼95% over an ultrawide range of wavelengths from 0.4 μm to 20 μm. The high absorption feature of the different bandgap materials is applied in this absorption device to realize the ultrabroadband absorption, combining with the metal-dielectric-like configuration for those unmatched-admittance wavelengths and the graded index profile arrangement for the 0.4–2.5 μm band. The proposed ultrabroadband absorber shows a great angular tolerance up to 60° with the average absorption of 90% remaining. The proposed approach can have tremendous potential in fields of optical sensing, camouflage, optical imaging, passive cooling, and sustainable power generation, profiting from the good mechanical characteristics of this compact multilayer film structure and the low manufacture costs with the simple physical vapor deposition.