Reconfigurable Gradient Index using VO$_2$ Memory Metamaterials

We have demonstrated tuning of a metamaterial device that incorporates a form of spatial gradient control. Electrical tuning of the metamaterial was achieved through a vanadium dioxide layer which interacts with an array of split ring resonators. Through design of the device and contact geometry, we achieved a spatial gradient in the magnitude of permittivity, writeable using a single transient electrical pulse. This induced gradient in our device was observed on spatial scales on the order of one wavelength at 1 THz. Thus we have demonstrated the viability of elements for use in future devices with potential applications in beamforming and communications.\footnote{M. D. Goldflam, \textit{et. al.}, Appl. Phys. Lett. 99, 044103 (2011).} Various contact geometries are currently being investigated with the goal of implementing finer control over gradients and expanding on the possible applications of such devices.