Optical Resonator Analog of a Two-Dimensional Topological Insulator

TL;DR

This paper demonstrates that a lattice of optical ring resonators can realize a topological insulator phase with robust edge states, achieved without fine-tuning couplings, using transfer matrix methods to analyze bandstructure and phase diagram.

Contribution

It introduces a new optical resonator system exhibiting topological insulator behavior without the need for fine-tuning inter-resonator couplings, unlike previous systems.

Findings

Robust edge states exist in the optical resonator lattice.

Topological phase occurs at strong couplings beyond tight-binding applicability.

System can function as a diode with gain and loss introduced.

Abstract

A lattice of optical ring resonators can exhibit a topological insulator phase, with the role of spin played by the direction of propagation of light within each ring. Unlike the system studied by Hafezi et al., topological protection is achieved without fine-tuning the inter-resonator couplings, which are given the same periodicity as the underlying lattice. The topological insulator phase occurs for strong couplings, when the tight-binding method is inapplicable. Using the transfer matrix method, we derive the bandstructure and phase diagram, and demonstrate the existence of robust edge states. When gain and loss are introduced, the system functions as a diode for coupled resonator modes.