Controllable Coupling of Localized and Propagating Surface Plasmons to Tamm Plasmons

We theoretically investigate the coupling between Tamm plasmons and localized surface plasmons (LSPs) as well as propagating surface plasmons (PSPs) in a multilayer structure consisting of a metallic nanowire array and a spatially separated metal-dielectric Bragg reflector (DBR). A clear anticrossing behavior of the resonances is observed in the dispersion diagram resulting from the coupling, which is well explained by the coupled oscillator model. The coupling also creates new hybrid LSP or PSP modes with narrow bandwidths and unique spectral features. Upon the excitation of these hybrid modes, the local fields underneath the nanowires for the hybrid LSPs or near the lower metal layer surface for the hybrid PSPs are both enhanced greatly as compared with those achieved in the structure without DBR, which has potential applications in nonlinear optics and surface-enhanced spectroscopies.