  The past decade has witnessed a booming development of topological photonics,
which revolutionizes the methodology for controlling the behavior of light. A
gigantic achievement is to engineer robust confined modes localized at
interfaces between topologically distinct regions, where the optical context
can trigger exotic topological phenomena exclusive to photons. Here, we provide
an experimentally flexible approach to engineering topologically induced
interface states in the visible regime via a unique design of complex
superlattice formed by connecting two component superlattices of distinguished
topological phases. Assisted by the intrinsic pseudospin degree due to the
splitting between TM and TE polarized modes, we attain a precise manipulation
of the spin-dependent topological interface states that can manifest themselves
straightforwardly through transmission spectra. More specifically, since these
topological localized modes stem from the hybridization of artificial photonic
orbitals that are of topological origin as well, they are deemed as a novel
topological effect and thus named as the secondary topological interface
states. Our work develops an innovative and productive strategy to tune
topologically protected localized modes, based on which various applications
such as selective local enhancement can be exploited.
