Fractal plasmonic metamaterial with tunable properties in the near-infrared

Modulating the fractal dimension of nanoporous gold is possible to tune the effective dielectric response over a wide spectral range of infrared wavelengths. The plasma edge and effective plasma frequency depend on the fractal dimension, which can be controlled by varying the preparation condition. The fractal porous metal has superior plasmonic properties compared to bulk gold. The long skin depth of porous metal 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 selfsimilar metamaterials.