Theory of multicolor soliton microcombs

TL;DR

This paper develops a comprehensive theoretical framework for multicolor soliton microcombs, revealing how engineered dispersion and multi-frequency pumping influence their formation and thresholds, with predictions validated by simulations.

Contribution

It introduces a general multiple-scale theory for multicolor soliton microcombs, highlighting the effects of dispersion engineering and multi-frequency pumping on their thresholds and formation.

Findings

Multi-frequency pumping lowers the threshold for comb formation.

Soliton microcombs can form with a single driving field.

The theory aligns well with numerical simulations.

Abstract

We present a general theory of multicolor soliton microcombs. These frequency combs require specially engineered dispersion and have an optical spectrum consisting of multiple spectral windows, centered at distinct frequencies. Our theory is based on a multiple-scale approach applied to the Lugiato-Lefever equation, and provides a framework to investigate different pumping configurations. For multi-frequency pumping, we predict a progressively lower pumping threshold as the number of spectral windows increases due to an enhancement of the effective nonlinear parameter. However, multi-frequency pumping is not a prerequisite for the formation of these combs and can emerge even with a single driving field. Our theoretical predictions are in excellent agreement with numerical simulations.