Photonic topological insulator induced by a dislocation in three dimensions

Area of Science:

• Photonics
• Condensed Matter Physics
• Topological Materials

Background:

• Topological insulators (TIs) exhibit unique edge states for scatter-free wave propagation.
• While 2D photonic TIs are established, 3D TIs at optical frequencies remain experimentally challenging.
• Existing 3D topological systems in acoustics and microwaves often rely on dislocations for protection.

Purpose of the Study:

• To experimentally realize a three-dimensional (3D) topological insulator at optical frequencies.
• To demonstrate topological protection in 3D photonic surface states.
• To explore the use of synthetic dimensions for creating novel topological photonic systems.

Main Methods:

• Utilized a 2D photonic waveguide array and introduced a synthetic modal dimension to create a 3D system.
• Engineered a screw dislocation within the lattice to induce topological properties.
• Investigated the behavior of edge states in the engineered 3D photonic topological insulator.

Main Results:

• Successfully demonstrated a 3D photonic topological insulator with protected topological surface states.
• Observed edge states propagating along 3D trajectories, exhibiting topological protection.
• The screw dislocation was key to enabling these protected 3D surface states.

Conclusions:

• This work presents the first experimental realization of a 3D photonic topological insulator at optical frequencies.
• The engineered system offers robust topological protection for light propagation.
• Paves the way for advanced applications of 3D topology in photonic science and technology.