We present aperiodic multilayer structures with ultrabroadband near-perfect absorption in the visible and near-infrared wavelength range. We use a hybrid optimization algorithm coupled with the transfer-matrix method, to optimize both the material composition and the layer thicknesses of the aperiodic multilayer structures that are composed of infinite slabs of material above a semi-infinite substrate. In order to achieve ultrabroadband near-perfect absorption, we consider a broad range of materials including dielectrics, metals, and semiconductors. The optimization algorithms previously used to design ultrabroadband near-perfect absorbers only optimized the layer thicknesses of structures with fixed material composition. In contrast, we find that our approach of simultaneously optimizing the material composition as well as the layer thicknesses leads to structures with broader near-perfect absorption. For an optimized eleven-layer structure the lower and upper absorption band edges are 400 nm and $\sim$3800 nm, respectively. In addition, we find that, even though the structures are optimized for normally incident light, the absorption is high in a broad angular range within the wavelength range of interest. We also explain the physical origin of ultrabroadband absorption in these structures. Our results will contribute to the development of a new generation of devices for solar photovoltaics, imaging, and photodetection.

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具有超宽带近乎完美吸收的优化多层结构

我们提出了在可见光和近红外波长范围内具有近乎完美吸收的超宽带非周期性多层结构。我们使用混合优化算法与传递矩阵方法相结合，以优化非周期性多层结构的材料成分和层厚度，这些结构由半无限衬底上方的无限材料板组成。为了实现超宽带近乎完美的吸收，我们考虑了广泛的材料，包括电介质、金属和半导体。以前用于设计超宽带近乎完美吸收器的优化算法仅优化了具有固定材料成分的结构的层厚度。相比之下，我们发现我们同时优化材料成分和层厚度的方法导致结构具有更广泛的近乎完美的吸收。对于优化的十一层结构，下吸收带边缘和上吸收带边缘分别为 400 nm 和 $\sim$3800 nm。此外，我们发现，即使结构针对垂直入射光进行了优化，但在感兴趣的波长范围内的宽角度范围内吸收率很高。我们还解释了这些结构中超宽带吸收的物理起源。我们的研究结果将有助于开发用于太阳能光伏、成像和光电检测的新一代设备。对于优化的十一层结构，下吸收带边缘和上吸收带边缘分别为 400 nm 和 $\sim$3800 nm。此外，我们发现，即使结构针对垂直入射光进行了优化，但在感兴趣的波长范围内的宽角度范围内吸收率很高。我们还解释了这些结构中超宽带吸收的物理起源。我们的研究结果将有助于开发用于太阳能光伏、成像和光电检测的新一代设备。对于优化的十一层结构，下吸收带边缘和上吸收带边缘分别为 400 nm 和 $\sim$3800 nm。此外，我们发现，即使结构针对垂直入射光进行了优化，但在感兴趣的波长范围内的宽角度范围内吸收率很高。我们还解释了这些结构中超宽带吸收的物理起源。我们的研究结果将有助于开发用于太阳能光伏、成像和光电检测的新一代设备。