Tunable metamaterial device for THz applications based on BaSrTiO3 thin film

Design, fabrication and characterization of an active single-negative metamaterial device in the terahertz (THz) spectrum is presented. The device is constructed by vertical split-ring unit cells which incorporate a Ba0.6Sr0.4TiO3 (BST) thin film whose dielectric constant can be altered by applying DC bias to change the capacitance of the split-ring resonators. A numerical model of the device that predicts a resonant frequency as a function of BST dielectric constant is presented. The resonant frequency shift due to the applied DC bias is experimentally verified and correlated with the model. The resonant frequency shift occurs as a direct result of the bias controlled index of refraction change in BST which significantly enhances the device response speed and durability compared with previously demonstrated micro-electro-mechanical systems based tunable metamaterial devices. In addition, this device can be used to characterize dielectric properties of the tunable oxide thin films in low THz spectrum (such as tunability) for many applications.