Enlargement of the band gap in the metal–insulator–metal heterowaveguide

We present a new metal–insulator–metal (MIM) heterowaveguide to enlarge the band gap, which is formed by alternately stacking two kinds of metals, modulating the MIM waveguide slit, and inserting different dielectric materials with the effective refractive index periodically modulated. Based on this structure, we adopt two different methods to enlarge the band gap: changing the thickness of the unit layer and combining two MIM structures. Both of them widen the band gap when surface plasmon polaritons propagate through the structure. This metal heterostructure is expected to have applications in surface plasmon polaritons (SPPs) based optical devices, such as filters, waveguides, especially for broad band gap elements.