Narrow-band plasmon absorption enabled by manipulating geometric phase of plasmonic waveguides

Abstract

We investigate the relationship between the absorption performance and the topological properties of metal-dielectric-metal (MDM) plasmonic waveguides, where 1D photonic crystals are inserted inside the waveguide core. We demonstrate that the reflection phase, within the bandgaps of the considered MDM waveguide, is related to both the geometric Zak phase in a bulk band and the formation of the optical Tamm state. The strong field confinement induced by the optical Tamm state results in narrow-band absorption of the propagating surface plasmons. We also show that both the reflection phase and the bandgap topological characteristics of the MDM waveguide can be manipulated by varying the geometric parameters of the inserted photonic crystals. By suitably designing the topological properties of the plasmonic waveguide, narrow-band plasmon absorption is achieved at specific bandgaps. An absorption band with a linewidth smaller than 7 nm and a high quality factor of 91.5 is obtained which can potentially be used for filtering, sensing, imaging, etc. Our work provides a novel way to design topological plasmonic devices for nanoscale integrated photonic circuits.