Investigating the physics of simultaneous breakdown events in metamaterials with multi-resonant unit cells

Under high power illumination, electromagnetic metamaterials and periodic structures experience internal breakdown that alters their frequency responses. It was recently demonstrated that a breakdown discharge created at a given location within the unit cell of a metamaterial mediates the breakdown at other locations within that unit cell or at the neighboring unit cells in spite of the fact that the intensity of the incident field is not high enough to cause breakdown at these other locations under normal situations. In this paper, we investigate the physics behind this phenomenon and examine three candidate mechanisms for these simultaneous breakdown discharges. These include energetic electron transport, ultraviolet (UV) radiation, and vacuum ultraviolet (VUV) radiation. By experimentally examining the unit cell of a metamaterial composed of multiple resonators, we were able to selectively isolate the coupling influence of the candidate mechanisms. It was established that VUV radiation from the initial discharge yields simultaneous breakdown at the other locations of interest.