Quasi-edge states and topological Bloch oscillation in the synthetic space

TL;DR

This paper proposes a theoretical model for topologically protected light transmission in a synthetic two-dimensional lattice created by dynamically-modulated waveguide arrays, revealing quasi-edge states and topological Bloch oscillations with potential on-chip applications.

Contribution

It introduces a novel model combining synthetic dimensions and topological effects in lithium niobate waveguides, demonstrating exotic edge states and Bloch oscillations in a unified framework.

Findings

Discovery of quasi-edge states with non-boundary intensity distribution

Observation of topological Bloch oscillation in frequency dimension

Potential for on-chip topological light transmission applications

Abstract

In physics, synthetic dimensions trigger great interest to manipulate light in different ways, while in technology, lithium niobate shows important capability towards on-chip applications. Here, based on the state-of-art technology, we propose and study a theoretical model of dynamically-modulated waveguide arrays with the Su-Schrieffer-Heeger configuration in the spatial dimension. The propagation of light through the one-dimensional waveguide arrays mimics time evolution of field in a synthetic two-dimensional lattice including the frequency dimension. By adding the effective gauge potential, we find quasi-edge state that the intensity distribution manifests not at the boundary as the traditional edge state, which leads to an exotic topologically protected one-way transmission along adjacent boundary. Furthermore, a cosine-shape isolated band exhibits, supporting the topological Bloch oscillation in the frequency dimension under the effective constant force, which is localized at the spatial boundary and shows the topological feature. Our work therefore points out further capability of light transmission under topological protections in both spatial and spectral regimes, and provides future on-chip applications in the lithium niobate platform.