  In this study, we propose and experimentally demonstrate a novel kind of Tamm
plasmon topological superlattice (TTS) by engineering Tamm photonic crystals
(TPCs) belonging to a different class of topology. Utilizing specifically
designed double-layer metasurfaces etching on planar multilayered photonic
structures, the TPC that supports the Tamm plasmon photonic bandgap is realized
in the visible regime. Through the coupling of topological interface states
existing between different TPCs, hybrid topological interface states of Tamm
plasmon, called supermodes, are obtained that can be fully described by a
tight-binding model. Meanwhile, we can achieve a tunable bandwidth of
supermodes via varying the etching depth difference between double-layer
metasurfaces. We show that the bandwidth decreases with the increase of etching
depth difference, resulting in a nearly flat dispersion of supermodes with
strong localization regardless of excitation angles. All the results are
experimentally verified by measuring angular-resolved reflectance spectra. The
TTS and supermodes proposed here open a new pathway for the manipulation of
Tamm plasmons, based on which various promising applications such as integrated
photonic devices, optical sensing, and enhancing light-matter interactions can
be realized.
