Realizing perfect light absorption in stacked thin films of dielectrics and metals through critical light coupling has recently received intensive research attention. In addition, realizing ultra-thin perfect absorber and tunable perfect absorber in the visible spectrum is essential for novel optoelectronics applications. However, the existing thin film stacks cannot show tunable perfect absorption in a wide-angle range. Here, a tunable perfect absorption from normal incidence to a wide-angle range (0° to 70°) by utilizing a two-layer stack consisting of a high refractive index low-loss dielectric on a high reflecting metal is proposed. This is experimentally demonstrated by depositing a thin layer of low-loss phase change material such as stibnite (Sb₂S₃) on a thin layer of silver. This structure shows tunable perfect absorption with large spectral tunability in the visible wavelength. Furthermore, the absorption enhancement in 2D materials by transferring monolayer molybdenum disulfide on the stack, which shows 96% light absorption with enhanced photoluminescence, is demonstrated. In addition, the thin film stack can work as a scalable phase modulator offering a maximum phase tunability of ≈140° by changing the structural state of Sb₂S₃ from amorphous to crystalline.

中文翻译：

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具有低损耗相变材料的纳米光子光学涂层中的广角可调谐临界耦合

通过临界光耦合在电介质和金属的堆叠薄膜中实现完美的光吸收最近受到了广泛的研究关注。此外，在可见光谱中实现超薄完美吸收体和可调谐完美吸收体对于新型光电应用至关重要。然而，现有的薄膜堆叠无法在广角范围内显示出可调谐的完美吸收。在这里，通过利用由高反射率金属上的高折射率低损耗电介质组成的两层堆叠，提出了从法向入射到广角范围（0° 至 70°）的可调完美吸收。这通过沉积薄层低损耗相变材料如辉锑矿（Sb ₂ S ₃) 在一层薄薄的银上。这种结构显示出可调谐的完美吸收，在可见光波长具有大的光谱可调性。此外，通过在叠层上转移单层二硫化钼来增强二维材料的吸收，显示出 96% 的光吸收和增强的光致发光。_{此外，通过将 Sb 2} S ₃的结构状态从非晶态转变为晶态，薄膜叠层可以用作可扩展的相位调制器，提供 ≈140° 的最大相位可调性。