Abstract

Metamaterials are a class of artificial materials designed to interact with light in ways no natural materials can.^1,2 Due to its resonant nature, the response of the metamaterials is very sensitive to the presence of dissipative losses in the metallic resonators. The several approaches to overcome the losses including the search for better plasmonic media, as well as direct compensation of losses by combining metamaterials with optical gain media were reported.^3,4 Those solutions, however, aim to minimize Joule losses, while in practice dissipation rates are often much higher than expected from the Ohm’s law. The additional drawback associated with surface roughness and grain boundary scattering due to polycrystalline nature of metal films were reported,⁵ and therefore employing single-crystal of noble metals can make a major contribution to the improvement of plasmonic losses. We demonstrated that single-crystal gold thin films grown on LiF substrates had smooth surfaces with root mean square (RMS) roughness of 0.2 nm and nanostructured metamaterials fabricated with these films had strong resonant response in the near-IR spectral range.⁶ In this work, we have developed a single-crystal silver thin film growth technique in order to reduce the losses further and extend the response wavelength.

© 2015 Japan Society of Applied Physics, Optical Society of America