Multi-color solitons and frequency combs in microresonators

TL;DR

This paper derives three-wave equations to describe multi-color solitons in microresonators, explaining observed frequency combs and the soliton-OPO effect, with implications for designing stable, low-noise frequency comb systems.

Contribution

It introduces a new theoretical framework with three-wave equations for multi-color solitons in microresonators with quartic dispersion, explaining experimental phenomena.

Findings

Derived three-wave equations for multi-color solitons

Explained interleaved frequency combs observed experimentally

Described conditions for soliton-OPO effect occurrence

Abstract

Multi-color solitons that are parametrically created in dual-pumped microresonators generate interleaved frequency combs that can be used to obtain combs at new frequencies and when synchronized can be used for low-noise microwave generation and potentially as an element in a chip-scale clockwork. Here, we first derive three-wave equations that describe multi-color solitons that appear in microresonators with a nearly quartic dispersion profile. These solitons are characterized by a single angular group velocity and multiple angular phase velocities. We then use these equations to explain the interleaved frequency combs that are observed at the output of the microresonator. Finally, we used these equations to describe the experimentally-observed soliton-OPO effect. In this effect, the pump frequency comb interacts nonlinearly with a signal frequency comb to create an idler frequency comb in a new frequency range, analogous to an optical parametric oscillation (OPO) process. We determine the conditions under which we expect this effect to occur. We anticipate that the three-wave equations and their extensions will be of use in designing new frequency comb systems and determining their stability and noise performance.