Plasmonic Cu nanostructures in ZnO as hyperbolic metamaterial thin films

Plasmonic metals, such as Cu and Al, have been considered as potential low-loss alternatives for Au and Ag for photonic structures and devices. However, challenges remain in the fabrication and applications of Cu nanostructures, because of its easy oxidation issues. In this work, a new metamaterial structure of plasmonic Cu nanostructures embedded in a dielectric ZnO matrix has been designed and successfully fabricated using a one-step thin film growth method. The Cu–ZnO hybrid thin films present excellent epitaxial quality and exotic optical properties, such as strong localized surface plasmon resonance in the visible regime, and, highly anisotropic and hyperbolic optical response, revealed by angular dependent and polarization resolved reflectivity measurements. This hyperbolic plasmonic metamaterial via the metal-in-oxide matrix form combining low-loss plasmonic Cu nanostructures and extraordinary anisotropic optical properties could be used towards various nanophotonic applications, such as plasmonic solar energy devices and hyperlens.