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

Abstract

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.

Wavelength‐Selective Light Trapping with Nanometer‐Thick Metallic Coating

“…To further broaden the working wavelength range for applications such as solar-thermal conversion, [8,9,20,25,26] photovoltaic conversion, [27][28][29][30][31][32][33][34] optical imaging, [24] stray light elimination, [35] etc., an additional lossless dielectric film is added on the top of the asymmetric resonant cavity MPA in Figure 1e to achieve the broadband absorption with high efficiency, as shown in Figure 1g. The thickness of the absorptive metal increases from 4 to 20 nm and the additional dielectric works as the antireflection coating (ARC) to reduce the high reflection caused by the thicker metallic coating.…”

“…As the engineering of the optical properties of the lossy semiconductor material is complicated and uncontrollable, realizing efficient wavelength-selective broadband light trapping with sub-wavelength optical coatings consisting of alternate semiconductor-dielectric or metal-dielectric stacks has remained an elusive challenge. [20][21][22][23][24] In this article, we introduce a compact film structure that presents perfect absorption either at a single wavelength or across a broad band using a nanometer-thick single-layer metallic coating. The compact coating mirror|phase tuning layer|absorptive metal (MPA) works like an asymmetric resonant cavity to enhance the absorption efficiency within the nanometer metallic layer up to %100%.…”

“…As the engineering of the optical properties of the lossy semiconductor material is complicated and uncontrollable, realizing efficient wavelength‐selective broadband light trapping with sub‐wavelength optical coatings consisting of alternate semiconductor–dielectric or metal–dielectric stacks has remained an elusive challenge. [ 20–24 ]…”

Using Time-Varying Systems to Challenge Fundamental Limitations in Electromagnetics

“…Clearly, the absorption bandwidth can therefore be enlarged by increasing the thickness of the absorber or the tolerable reflection coefficient. Prominent examples of broadband absorbers include cascaded [87], [88] or adiabatically tapered [89], [90], [91] structures which typically have thicknesses on the order of several wavelengths. However, for many applications, such as radar absorbing or solar energy harvesting, a thin absorber with a large bandwidth is highly desirable due to practical and economic reasons, which motivates the large interest in overcoming the "Rozanov bound".…”

Nanostructured Ge/ZnS Films for Multispectral Camouflage with Low Visibility and Low Thermal Emission

“…Over the past years, electromagnetic absorbers in the visible and IR regions have been extensively researched for solar–thermal conversion, − optical sensing, − detection, , and radiation cooling. − However, in the above planar nanostructures or nanopatterns, high electric conductivity components like metals are necessary as lossy materials to absorb visible or IR light, which would block microwave transmission. As a result, these structures cannot be amenable to the demand of being compatible with microwave camouflage.…”