Topological supermodes in a specialty periodic tri-lattice optical waveguide

Abstract

Topological photonic waveguides are immensely being investigated owing to the unique features of topology-protected light transmission. Here, we present the signature of topological supermodes in a specialty topological tri-lattice fiber endowed with one-dimensional (1D) periodic lattices. The topological fiber comprises a nontrivial lattice sandwiched between two identical trivial lattices leading to the formation of two interfaces. The presence of two interface states within the same topological bandgap has been observed in the transmission study of the tri-lattice fiber. Moreover, the finite element method-based analysis of the tri-lattice geometry exhibits two identical waveguide modes at two different wavelengths corresponding to the two interface states confined within the nontrivial lattice. The nearly identical propagation constants of the two modes indicate the formation of a supermode in such a periodic waveguide geometry. It is also shown that there are limitations of the fiber geometry for which detectable supermodes exist, and they are robust against a limited amount of local imperfections like layer thickness variation. Such observations intrigue further investigation towards novel topology-based photonic waveguides for strong and secure information transmission in quantum communication.