Detecting the Berry curvature in photonic graphene

TL;DR

This paper presents a method to measure Berry curvature in photonic graphene using wave-packet dynamics in optical waveguides, enabling the exploration of topological properties in photonic systems.

Contribution

The authors introduce a difference measurement technique to extract Berry curvature in photonic graphene, accounting for strain and sublattice bias effects, with potential for experimental implementation.

Findings

Berry curvature can be measured with negligible error in photonic graphene.

Strain preserves the Berry curvature texture across the Brillouin zone.

The method is robust against small sublattice biases and strain effects.

Abstract

We describe a method for measuring the Berry curvature from the wave-packet dynamics in perturbed arrays of evanescently coupled optical waveguides with honeycomb lattice structure. To disentangle the effects of the Berry curvature and the energy dispersion we utilize a difference measurement by propagating the wave packet under the influence of a constant external force back and forth. In this way a non-vanishing Berry curvature is obtained for photonic graphene with small sublattice bias or strain, where the relative error between the exact Berry curvature and the one derived from the semiclassical dynamics is negligible. For the strained lattice we demonstrate the robustness of the Berry curvature texture over the Brillouin zone compared to the energy dispersion. We also comment on the experimental realization of the proposed Berry curvature mapping in photonics.