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We examine the optical properties of two-dimensionally nanostructured metals in the metamaterial regime for infrared applications. Compared with straight nanowires and nanogrids, serpentine structures exhibit much lower optical losses of less than 7% even at a large metal area fraction of 0.3. The low loss is primarily due to a small effective conductivity of the meandering structures, and self-inductance plays a modest role in reducing losses in these structures. The high transparency at a large metal area coverage would be useful for transparent electrodes in optoelectronic devices.

We develop a model to describe the optical properties of periodic surpentine structures in the metamaterial regime. The structures are essentially transparent to infrared radiation and would be useful for transparent electrodes. The model predictions for the absorptance and the reflectance of the serpentine structures show a good agreement with numerical calculations of Maxwell’s equations. Our model reveals that the absorptance of the serpentine structures is determined by the self-inductance and the reflectance is affected by both the self-inductance and the effective conductivity. The effective conductivity is shown to be a dominant effect to reduce reflection.