Plasma-tunable metamaterials and periodic structures

In this paper, we examine methods in which plasmas can be used to tune the responses of RF/microwave periodic structures and artificially-engineered materials. In particular, we exploit microwave-induced plasmas created in periodic structures when the power of the incident electromagnetic wave exceeds the breakdown threshold power level. Based on the nature of the plasma created within the unit cell of a periodic structure, the structure can either be physically reconfigured or its impedance can be changed continuously. The former phenomenon results in a reconfigurable (or switchable) periodic structure and the latter results in a tunable one. We examine this phenomenon in several planar periodic structures, which are designed to be opaque at microwave frequencies. We demonstrate that these structures can be made transparent when the devices are driven to breakdown in air at atmospheric pressure. We also discuss the behavior of these structures when the plasma is created in Argon at different pressure levels.