A theory of light reflection and transmission by an optically thin nanocomposite slab that contains randomly distributed metal nanoparticles (NPs) is developed. The underlying model treats NPs as point dipoles and employs a dyadic Green’s function known analytically for a slab that allows one to obtain the refection and transmission coefficients in a fully analytical form. The model also takes into account the enhanced decay of localized surface plasmons in dense NP arrays and light scattering at the slab surface roughness. It is demonstrated that the first effect leads to broadband perfect absorption observed in such nanocomposites, whereas the second one is responsible for its omnidirectional character and polarization insensitivity. These findings open up new possibilities to engineer broadband perfect absorption in plasmonic nanocomposites.

中文翻译：

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等离子体纳米复合板的光反射和透射理论：宽带完全吸收的出现

建立了一种光学反射和透射的理论，该理论是通过包含无规分布的金属纳米颗粒（NPs）的光学薄纳米复合材料平板进行的。基本模型将NP视为点偶极子，并采用分析格林已知的平板格林函数，从而可以以完全解析的形式获得反射率和透射系数。该模型还考虑了密集NP阵列中局部表面等离子体激元的增强衰减以及平板表面粗糙度处的光散射。结果表明，第一种作用导致在这种纳米复合材料中观察到宽带完美吸收，而第二种作用则是其全向特性和极化不敏感性的原因。这些发现为在等离子体纳米复合材料中实现宽带完美吸收提供了新的可能性。