Dual-Polarization Second-Order Photonic Topological Insulators

TL;DR

This paper introduces a dual-polarization second-order photonic topological insulator that supports highly localized, defect-robust corner states for both TE and TM modes, enabling polarization-independent photonic devices.

Contribution

It proposes a novel dual-polarization photonic crystal structure optimized via topology methods, revealing topological features with simple models and demonstrating robust corner states.

Findings

Supports four groups of corner states with different profiles and frequencies for TE and TM modes.

Corner states exhibit robustness against defects.

Enables polarization-independent topological photonic devices.

Abstract

Second-order photonic topological insulators that host highly localized corner states resilient to defects, are opening new routes towards developing fascinating photonic devices. However, the existing works on second-order photonic topological insulators have mainly focused on either transverse magnetic or transverse electric modes. In this paper, we propose a dual-polarization topological photonic crystal structure for both transverse magnetic and transverse electric modes through topology optimization. Simple tight-binding lattice models are constructed to reveal the topological features of the optimized photonic crystal structure in a transparent way. The optimized dual-polarization second-order photonic topological insulator hosts four groups of corner states with different profiles and eigenfrequencies for both the transverse magnetic and transverse electric modes. Moreover, the robustness of theses corner states against defects is explicitly demonstrated. Our results offer opportunities for developing polarization-independent topological photonic devices.