Coupling and protection effects of Jackiw-Rebbi states and trivial states in interfaced binary waveguide arrays

We systematically study different scenarios of interaction between two localized structures which were both found recently in interfaced binary waveguide arrays with alternating signs of the Dirac mass in the linear and nonlinear regimes of Kerr type. The first localized structure is the optical analog of the famous Jackiw-Rebbi state emerging from the Dirac equation in quantum field theory, and the second one is the trivial state. We show that two localized states of different types practically do not interact at all; thus, they can be protected from each other in a reliable way. Meanwhile, two localized states of the same type can couple efficiently with each other and show the nonlinear switching effect like in well-known symmetric fiber couplers. © 2020 American Physical Society.