Abstract
Multistability in Kerr resonators which are driven by continuous or modulated optical waves gives rise to the superposition of distinct nonlinear states, yielding a unique platform for studying complex soliton dynamics. Here, by pumping a crystalline microresonator with two lasers that are frequency detuned from each other by one or multiple cavity free spectral ranges, we go beyond the traditional bichromatic pumping framework and enter an unexplored multistability regime that allows observing novel dynamics including composite solitons and successive soliton collisions. We generate complex frequency comb patterns, observing the velocity mismatch between the solitons and the dual-pumping-induced lattice traps and showing the synchronization of the repetition rates of constituent distinct solitons under the influence of index-barrier-induced intersoliton repulsion. We also demonstrate soliton collisions and observe transient soliton response with spectral analysis and ultrafast imaging, highlighting the eigenfrequency of dissipative soliton dynamics that coincides the “soliton () resonance.” Furthermore, we exploit the higher-order dispersion effect to manipulate the intrinsic group velocity mismatch between distinct solitons and demonstrate reversible switching between the composite soliton state and the soliton collisional state. Our findings bring to light the rich physics of the Kerr multistability and may equally be useful in microcomb-based spectroscopy and metrology.
5 More- Received 13 May 2019
- Revised 24 December 2019
- Accepted 19 February 2020
DOI:https://doi.org/10.1103/PhysRevX.10.021017
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Popular Summary
Solitons are ubiquitous, self-reinforcing, particlelike, wave packets that emerge in hydrodynamics, cold atoms, and plasmas. When a laser field is confined in a circular resonator with ultralow loss, multiple solitons traveling around the resonator can be generated. Normally, these solitons travel with the same speed, so they rarely get close to each other. Here, we report the generation of controlled soliton collisions, upon which the solitons exhibit unique features that we have directly captured with an ultrafast sampling technique.
We use two lasers to excite two soliton species in a resonator, where the soliton speed difference can be controlled with the laser frequency mismatch. Depending on the speed difference, different solitons can bind with each other after they collide, or they can cross each other repeatedly. Since each collision happens in a very short time, usual techniques cannot resolve the detailed soliton behaviors.
To capture these collision behaviors, we mix the output of the solitons by the resonator with a series of rapid laser pulses. The interference between the pulses and the solitons generates electronic signals that we record and analyze, allowing us to compare the collisions with theoretical simulations that accurately predict the experimental observations.
While our work introduces a convenient yet powerful platform to study complex soliton interactions and transient nonlinear dynamics, it could also have practical implications for the generation of synchronized frequency combs and soliton-based optical telecommunication.