Abstract
Dissipative Kerr solitons are localized structures that exist in optical microresonators. They lead to the formation of microcombs --- chip-scale frequency combs that could facilitate precision frequency synthesis and metrology by capitalizing on advances in silicon photonics. Previous demonstrations have mainly focused on anomalous dispersion microresonators. Notwithstanding, localized structures also exist in the normal dispersion regime in the form of circulating dark pulses, but their physical dynamics is far from being understood. Here, we report the discovery of reversible switching between coherent dark-pulse Kerr combs, whereby distinct states can be accessed deterministically. Furthermore, we reveal that the formation of dark-pulse Kerr combs is associated with the appearance of a new resonance, a feature that has never been observed for dark-pulses and is ascribed to soliton behavior. These results contribute to understanding the nonlinear physics in few-mode microresonators and provide insight into the generation of microcombs with high conversion efficiency.
Highlights
Dissipative solitons are self-enforcing, stationary structures that exist in diverse nonlinear dissipative systems subject to an external pump of energy [1]
While the observations reported here have been made in a normal dispersion microresonator, similar results might be found in nonlinear systems with selffocusing nonlinearity and normal dispersion, such as fiber ring cavities, Bose-Einstein condensates, or hydrodynamics [33,38,39]
The same microresonator, pumped in the same way, has been previously used to generate a modelocked Kerr frequency comb, with evidence of dark pulses circulating in the cavity [36]
Summary
Dissipative solitons are self-enforcing, stationary structures that exist in diverse nonlinear dissipative systems subject to an external pump of energy [1]. The time-domain waveform of a dark-pulse Kerr comb corresponds to a localized dark-pulse structure, where low-intensity oscillations are embedded in a high-intensity background These pulses can be interpreted as two stably interlocked switching waves, connecting the upper and lower homogeneous steady-state solutions of the bistability curve in Kerr cavities [30]. We report deterministic switching between dark-pulse Kerr comb states and support our results with numerical simulations that take into account the linear coupling between the dominant transverse modes of the microresonator. The numerical analysis shows that each comb state is uniquely ascribed to a number of low-intensity oscillation periods This number can be deterministically controlled and increased or decreased one at a time, unraveling an overlooked dependence with the pump laser detuning parameter for dark-pulse Kerr combs. While the observations reported here have been made in a normal dispersion microresonator, similar results might be found in nonlinear systems with selffocusing nonlinearity and normal dispersion, such as fiber ring cavities, Bose-Einstein condensates, or hydrodynamics [33,38,39]
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