Topologically protected frequency control of broadband signals in dynamically modulated waveguide arrays

TL;DR

This paper proposes a topological approach using synthetic frequency dimensions in modulated waveguide arrays to achieve robust control of broadband optical signals, avoiding the limitations of cavity-based methods.

Contribution

It introduces a novel topological scheme for broadband frequency control using a synthetic space-frequency lattice in waveguides, expanding beyond cavity-based techniques.

Findings

Identification of non-trivial topological band structures in the synthetic lattice

Demonstration of chiral edge states for robust frequency manipulation

Potential for broadband signal processing without high-Q cavities

Abstract

We theoretically propose a synthetic frequency dimension scheme to control the spectrum of a light beam propagating through an array of evanescently coupled waveguides modulated in time by a propagating sound wave via the acousto-optical effect. Configurations are identified where the emerging two-dimensional synthetic space-frequency lattice displays a non-trivial topological band structure. The corresponding chiral edge states can be exploited to manipulate the frequency spectrum of an incident beam in a robust way. In contrast to previous works, our proposal is not based on discrete high-Q cavity modes, which paves the way to the manipulation of broadband signals.