Observation of breathing dark pulses in normal...

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Breathers are localized waves that are periodic in time or space. The concept of breathers is useful for describing many nonlinear physical systems including granular lattices, Bose-Einstein condensates, 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 the observation of breathing dark pulses in normal dispersion silicon nitride microresonators. These Kerr combs breathe gently and retain dark-localized waveforms, while exhibiting energy exchange between some central spectral lines and the lines in the wings. A transition to a chaotic dark breathing state via period-tripling is observed by increasing the pump power. The breathing dark pulse dynamics are well reproduced by numerical simulations based on the Lugiato-Lefever equation. The results also reflect the importance of dissipation to breathing dark pulse dynamics in microresonators and give new insights into high power dark pulse Kerr combs from normal dispersion microresonators.


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