In this work, we show that modulating the fractal dimension of nanoporous gold allows its effective dielectric response to be tailored over a wide spectral range of infrared wavelengths. In particular, the plasma edge and effective plasma frequency depend linearly on the fractal dimension, which can be controlled by varying the pore and ligament sizes. Importantly, the fractal porous metal exhibits superior plasmonic properties compared to its bulk counterpart. These properties, combined with a longer skin depth on the order of 100–200 nm, enables the penetration of optical energy deep into the nanopores where molecules can be loaded, thus, achieving more effective light–matter coupling. These findings may open new pathways to engineering the optical response of fractal-like or self-similar metamaterials without the need for sophisticated lithographic patterning.

中文翻译：

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在近红外中具有可定制的等离子体频率的分形等离子体等离子超材料

在这项工作中，我们表明，调节纳米多孔金的分形维数可以使其有效的介电响应在红外波长的宽光谱范围内进行定制。特别地，等离子体边缘和有效等离子体频率线性地取决于分形维数，其可以通过改变孔和韧带的大小来控制。重要的是，分形多孔金属与其本体的多孔金属相比具有更好的等离子体性能。这些特性与更长的趋肤深度（100-200 nm数量级）相结合，可使光能深入到可以装载分子的纳米孔中，从而实现更有效的光-质耦合。