Study of Resonant Leaky Edge States in Simple Topological Photonic Lattices

Abstract The properties of topological edge states of resonant photonic lattices are reported. The canonical 1D lattice embodies all chief qualities necessary for a complete comprehension of the variety of fundamental physical processes at play. Radiating topological edge states are understood in terms of leaky‐mode resonance stimulated by counter‐propagating Bloch modes. As a free‐space electromagnetic wave illuminates the junction between band‐flipped photonic lattices, quasi‐leaky resonant light is localized at the interface, which embodies the characteristics of the closed‐band state of the composite lattice. Rigorous numerical examples with Ge/ZnSe‐based lattices with a finite number of periods and having homogeneous sublayers illustrate the resonance properties of the constituent lattices, the band‐closed lattice, and the composite lattice hosting the radiant edge state. The topological interface is seen to radiate effectively near the wavelength where the band closes. With the insight gained from the 1D analysis, a representative 2D lattice is similarly treated. As orthogonal leaky modes are supported by 2D lattices, the interface‐bound energy flow picture is more intriguing. Thus, lateral TE and TM modes can be excited to run along the topological interface or normal to it. Versatile power flow, energy density, and radiation characteristics are then available at the 2D topological interface.