| In recent years, metamaterials have received a significant amount of attention for providing engineered artificial properties which do not exist in nature such as high surface impedance, negative permittivity/permeability, and negative refractive index. However, under high-power illuminations, metamaterials tend to breakdown and alter their frequency responses. This dissertation includes two parts. First, I investigate the phenomenon of electromagnetic (EM) waves tunneling through epsilon- and mu-negative metamaterial slabs and its potential applications in designing high-power filters and frequency selective surfaces without breakdown. The second part is to investigate breakdown events in high-power microwave metamaterials.;In this thesis, I examine EM waves tunneling through multi-layer structures composed of epsilon-negative (the relative permittivity is negative) materials sandwiched by double positive layers. Conventionally, EM waves can only propagate through epsilon-negative material under certain circumstance referred to as resonant tunneling. I demonstrate that this EM waves tunneling phenomenon is analogous to a well-known classic microwave filter theory. Based on this analogy, I proposed a synthesis procedure for designing this kind of structure from desired responses which are beneficial for developing high-power-capable spatial filters and microwave FSSs. To verify the proposed procedure, three prototypes of such a device are designed, fabricated and experimentally characterized and it is demonstrated that they can handle extremely high peak power levels.;In the second half of my thesis, I study the impact of breakdown on the responses of metamaterials by examining several single-layer metasurfaces composed of miniaturized LC resonators. I demonstrate that the breakdown events, in atmospheric air, can be characterized with a reasonable degree of accuracy by modeling the streaming discharge as a low-impedance connection path. My recent study shows that breakdown at one location induces breakdown at neighboring locations where the power level is lower than the breakdown threshold within a multi-resonator unit cell of high-power metamaterials with discrete nonlinear responses. I examine three candidate mechanisms, energetic electron diffusion, ultraviolet (UV) radiation, and vacuum ultraviolet (VUV) radiation, to study the cause of this simultaneous breakdown and demonstrated that this is due to VUV photoemission. |
