# Broadband topological slow light through higher momentum-space winding

## TL;DR

This paper proposes a novel edge termination in photonic topological insulators that enables slow light with broadband operation by causing the edge state to wind multiple times around the Brillouin zone, overcoming traditional bandwidth limitations.

## Contribution

It introduces a new method to achieve broadband slow light in topological photonic waveguides through higher momentum-space winding of edge states.

## Key findings

- Edge states can wind multiple times around the Brillouin zone.
- The approach enables slow and broadband light propagation.
- Theoretical demonstration of the winding effect on edge states.

## Abstract

Slow-light waveguides can strongly enhance light-matter interaction, but suffer from narrow bandwidth, increased backscattering, and Anderson localization. Edge states in photonic topological insulators resist backscattering and localization, but typically cross the bandgap over a single Brillouin zone, meaning that slow group velocity implies narrow-band operation. Here we show theoretically that this can be circumvented via an edge termination that causes the edge state to wind many times around the Brillouin zone, making it both slow and broadband.