Topological Dirac-vortex modes in a three-dimensional photonic topological insulator

Area of Science:

• Photonics
• Condensed Matter Physics
• Materials Science

Background:

• Topological Dirac-vortex modes in Kekulé-distorted photonic lattices are of great interest for robust photonic devices.
• Previous research was limited to 2D systems due to the complexity of 3D electromagnetic wave behavior.
• The vectorial nature of light complicates band structures, hindering the application of tight-binding models in 3D.

Purpose of the Study:

• To theoretically propose and experimentally demonstrate three-dimensional (3D) topological Dirac-vortex modes.
• To overcome the limitations of 2D systems by developing a 3D photonic topological insulator.
• To establish a platform for mapping 3D tight-binding models in photonic crystals.

Main Methods:

• Direct mapping of a 3D Kekulé-distorted tight-binding model.
• Fabrication of a 3D photonic crystal with scalar-wave-like band structures.
• Microwave near-field measurements to observe Dirac-vortex modes.

Main Results:

• Successful theoretical proposal and experimental demonstration of 3D topological Dirac-vortex modes.
• Observation of robust modes bound to and propagating along a 1D Dirac-vortex line defect.
• Experimental results align with tight-binding model predictions and simulations.

Conclusions:

• This work presents the first experimental realization of 3D topological Dirac-vortex modes in a photonic topological insulator.
• The study provides a direct method for mapping tight-binding models in 3D photonic systems.
• It opens new possibilities for controlling light in 3D space using topological lattice defects.