Plasmonic band gaps of structured metallic thin films evaluated for a surface plasmon laser using the coupled-wave approach

The behavior of plasmonic band gaps appearing in the dispersion relations of surface plasmons for periodically corrugated thin silver films is theoretically investigated by using the rigorous coupled-wave approach. The structures have one-dimensional rectangular corrugations with 25%, 50%, and 75% fill factors and support both long-range and short-range surface plasmon band gaps. A unified explanation for the necessary conditions for opening these band gaps, as well as intermode band gaps, is given. The radiation characteristics of the surface plasmons at the edges of these band gaps are also analyzed. Based on the findings, the optimal structure for a plasmonic band gap laser is presented.