Topological band structure via twisted photons in a degenerate cavity

TL;DR

This paper demonstrates a novel method to realize and control topological band structures using twisted photons in a degenerate optical cavity, advancing the exploration of higher-dimensional topological physics in photonic systems.

Contribution

It introduces a new approach to generate and study topological phenomena via synthetic dimensions created by photonic orbital and spin angular momentum in a compact cavity.

Findings

Characterized the density of states and energy band structures.

Observed topological windings in the system.

Controlled spin-orbital coupling in a driven photonic system.

Abstract

Synthetic dimensions based on particles' internal degrees of freedom, such as frequency, spatial modes and arrival time, have attracted significant attention. They offer ideal large-scale lattices to simulate nontrivial topological phenomena. Exploring more synthetic dimensions is one of the paths toward higher dimensional physics. In this work, we design and experimentally control the coupling among synthetic dimensions consisting of the intrinsic photonic orbital angular momentum and spin angular momentum degrees of freedom in a degenerate optical resonant cavity, which generates a periodically driven spin-orbital coupling system. We directly characterize the system's properties, including the density of states, energy band structures and topological windings, through the transmission intensity measurements. Our work demonstrates a novel mechanism for exploring the spatial modes of twisted photons as the synthetic dimension, which paves the way to design rich topological physics in a highly compact platform.