Dark breathers in a normal dispersion optical microresonator

TL;DR

This paper reports the first experimental and numerical observation of dark breathers in a normal dispersion silicon nitride microresonator, revealing their dynamics, control mechanisms, and transition to chaos, with implications for Kerr comb stability.

Contribution

It demonstrates the existence and control of dark breathers in normal dispersion microresonators, a phenomenon previously unobserved in this regime.

Findings

Dark breathers can be generated by tuning pump wavelength and power.

Dark breathers exhibit energy exchange between central and wing lines.

Transition to chaotic breather states occurs with increased pump power.

Abstract

Breathers are localized waves, that are periodic in time or space. The concept of breathers is useful for describing many physical systems including granular lattices, Bose-Einstein condensation, hydrodynamics, plasmas and optics. Breathers could exist in both the anomalous and the normal dispersion regime. However, the demonstration of optical breathers in the normal dispersion regime remains elusive to our knowledge. Kerr comb generation in optical microresonators provides an array of oscillators that are highly coupled via the Kerr effect, which can be exploited to explore the breather dynamics. Here, we present, experimentally and numerically, the observation of dark breathers in a normal dispersion silicon nitride microresonator. By controlling the pump wavelength and power, we can generate the dark breather, which exhibits an energy exchange between the central lines and the lines at the wing. The dark breather breathes gently and retains a dark-pulse waveform. A transition to a chaotic breather state is also observed by increasing the pump power. These dark breather dynamics are well reproduced by numerical simulations based on the Lugiato-Lefever equation. The results also reveal the importance of dissipation to dark breather dynamics and give important insights into instabilities related to high power dark pulse Kerr combs from normal dispersion microreosnators.