Dirac-vortex topological photonic crystal fibre

Area of Science:

• Photonics
• Condensed Matter Physics
• Materials Science

Background:

• Photonic crystal fibers (PCFs) are crucial for advanced optical applications.
• Their performance depends on the intricate 2D photonic crystal structures in their cross-section.
• Developing novel PCF designs with unique guiding properties is an ongoing research area.

Purpose of the Study:

• To propose a new type of photonic crystal fiber based on topological bandgaps.
• To demonstrate a design that utilizes generalized Kekulé modulation of a Dirac lattice with a vortex phase.
• To show that this design can achieve single-polarization, single-mode guidance over a wide bandwidth.

Main Methods:

• Theoretical proposal of a topological bandgap fiber.
• Utilizing generalized Kekulé modulation on a Dirac lattice with a vortex phase to open in-plane bandgaps.
• Analyzing the properties of mid-gap defect modes guided at the core.
• Relating the number of guiding modes to the winding number of the spatial vortex.

Main Results:

• A topological bandgap fiber design, termed Dirac-vortex fiber, is proposed.
• In-plane bandgaps are successfully opened by the generalized Kekulé modulation.
• Mid-gap defect modes are guaranteed to guide light at the fiber core.
• The number of guiding modes is precisely controlled by the vortex winding number.
• A single-vortex design achieves single-polarization, single-mode guidance over an octave bandwidth.

Conclusions:

• The proposed Dirac-vortex fiber offers a novel approach to designing photonic crystal fibers.
• Topological bandgaps provide a robust mechanism for light guidance.
• The ability to control the number of modes via the vortex winding number offers design flexibility.
• The octave-bandwidth, single-polarization, single-mode guidance is a significant advancement for optical applications.