Parametric conversion via second harmonic generation and two-hump solitons in phase-matched microresonators

TL;DR

This paper develops a theoretical framework for multimode second harmonic generation in microresonators, revealing how spectral tunability is controlled by Eckhaus instabilities and demonstrating the emergence of double-pulse solitons outside bistability regions.

Contribution

It introduces a new theory for multimode second harmonic generation in microresonators, highlighting the role of Eckhaus instabilities and describing novel double-pulse soliton states.

Findings

Spectral tunability governed by Eckhaus instabilities.

Transition to mode-locking and double-pulse solitons.

Existence of solitons outside bistability interval.

Abstract

Frequency conversion in microresonators has revolutionised modern-day nonlinear and quantum optics. Here, we present a theory of the multimode second harmonic generation in microresonators under conditions when the parametric conversion back to the pump spectrum dominates through the large domain in the resonator parameter space. We demonstrate that the spectral tunability of the sideband generation in this regime is governed by a discrete sequence of the so-called Eckhaus instabilities. We report the transition to modelocking and generation of solitons, which have a double-pulse structure in the pump field. These solitons exist outside the bistability interval and on a slightly curved background.