Electrical engineering

Physics

Transverse plane

Topology (electrical circuits)

Magnetization

Topological order

Structural engineering

Photonic crystal

Symmetry protected topological order

Magnetic field

Optics

Topological insulator

Engineering

Physical chemistry

Chemistry

Polarization (electrochemistry)

Photonics

Condensed matter physics

Quantum mechanics

Quantum

Polarization density

Physical Review Applied

Second-order photonic topological insulators that host highly localized corner states resilient to defects, are opening alternative 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 these corner states against defects is explicitly demonstrated. Our results offer opportunities for developing polarization-independent topological photonic devices.

Dual-Polarization Second-Order Photonic Topological Insulators