Frequency selective heterojunction metal-insulator-metal mirror for surface plasmons

Abstract

The authors introduce a mode-gap mirror for surface plasmon polaritons in a metal-insulator-metal (MIM) structure. At the heterojunction of MIMs which consists of two MIMs of different insulators, it is shown that a mode gap exists for a certain frequency range and the junction works as an effective mirror. Transmission and reflection properties of plasmonic modes at the interface of the heterojunction are investigated, and explained by the band theory. By showing that the mirror has high reflection and transmission of nearly zero, it is verified that the frequency range in which no plasmonic modes exist is an actual mode-gap range. It is also shown that by varying both the thickness and the dielectric constant of the insulator layer, one can select the frequency range in which the reflection coefficient is greater than 0.9.