Photonic Molecule Approach to Multiorbital Topology.

Area of Science:

• Photonics
• Condensed Matter Physics
• Topology

Background:

• Topology offers powerful methods for controlling wave propagation and localization.
• Engineered photonic degeneracies mimic electron spin states, enabling novel condensed matter-like phenomena.
• Photonic molecules, clusters of coupled waveguides, are promising platforms for exploring topological physics.

Purpose of the Study:

• To engineer and investigate topological states in optical waveguide arrays.
• To explore the role of engineered degeneracies and photonic molecules in creating topological phenomena.
• To understand topological transitions driven by lattice geometry and excitation wavelength.

Main Methods:

• Utilizing femtosecond laser-written waveguide arrays in the optical range.
• Implementing the photonic molecule concept for strong waveguide coupling.
• Analyzing topological modes protected by a Z3 invariant.

Main Results:

• Observation of unconventional topological modes protected by a Z3 invariant.
• Demonstration of topological transitions influenced by interorbital coupling and geometric dimerization.
• Tracking of multiple topological transitions by varying lattice spacings and excitation wavelength.

Conclusions:

• Engineered photonic degeneracies provide a route to novel topological phases.
• The Z3 invariant governs unique topological properties in coupled waveguide systems.
• This work opens new avenues for designing advanced photonic topological states and devices.