Dynamics of soliton crystals in optical microresonators (1903.07122v2)

Abstract: Dissipative Kerr solitons in optical microresonators provide a unifying framework for nonlinear optical physics with photonic-integrated technologies and have recently been employed in a wide range of applications from coherent communications to astrophysical spectrometer calibration. Dissipative Kerr solitons can form a rich variety of stable states, ranging from breathers to multiple-soliton formations, among which, the recently discovered soliton crystals stand out. They represent temporally-ordered ensembles of soliton pulses, which can be regularly arranged by a modulation of the continuous-wave intracavity driving field. To date, however, the dynamics of soliton crystals remains mainly unexplored. Moreover, the vast majority of the reported crystals contained defects - missing or shifted pulses, breaking the symmetry of these states, and no procedure to avoid such defects was suggested. Here we explore the dynamical properties of soliton crystals and discover that often-neglected chaotic operating regimes of the driven optical microresonator are the key to their understanding. In contrast to prior work, we prove the viability of deterministic generation of $\mathrm{perfect}$ soliton crystal states, which correspond to a stable, defect-free lattice of optical pulses inside the cavity. We discover the existence of critical pump power, below which the stochastic process of soliton excitation suddenly becomes deterministic enabling faultless, device-independent access to perfect soliton crystals. Furthermore, we demonstrate the switching of soliton crystal states and prove that it is also tightly linked to the pump power and is only possible in the regime of transient chaos. Finally, we report a number of other dynamical phenomena experimentally observed in soliton crystals including the formation of breathers, transitions between soliton crystals, their melting, and recrystallization.

Overview of Soliton Crystal Dynamics in Optical Microresonators

The paper "Dynamics of Soliton Crystals in Optical Microresonators" explores the formation, characterization, and dynamics of dissipative Kerr solitons (DKS), particularly focusing on soliton crystals within optical microresonators. Through a mix of experimental and theoretical approaches, the authors provide insights into how perfect soliton crystals—a special form of dissipative Kerr solitons—are deterministically generated and characterized by defect-free lattice arrangements of optical pulses.

Key Findings and Contributions

The paper primarily focuses on understanding the intricate dynamics and generation processes of soliton crystals, which manifest as ensembles of highly ordered soliton pulses in optical microcavities. Here are the key findings from the paper:

• Deterministic Generation of Soliton Crystals: A critical observation is the identification of a threshold pump power that aids in deterministic generation of perfect soliton crystal states. Below this critical power, traditionally stochastic processes turn deterministic, enabling faultless creation of soliton crystals with no defects and consistent repetition rates, which can be engineered up to the terahertz domain.
• Chaos and Stability Regimes: The research uncovers the influence of chaos—both spatiotemporal and transient—on soliton formation. Chaotic regimes influence the stability of soliton crystals and predefine the potential defect structures in soliton lattices. It is revealed that transient chaos significantly affects soliton state switching capabilities.
• Switching Dynamics: By developing analytical and experimental frameworks for soliton manipulation within the parameter space of pump power and detuning, the authors demonstrate the ability to switch soliton crystal states. Above another identified threshold power, solitons exhibit switching behavior, transitioning from one stable state to another and elucidating the control potential within these nonlinear systems.

Implications for Future Research

The findings have both practical and theoretical implications for nonlinear optics and signal processing. Practically, the deterministic generation of defect-free soliton crystals holds promise for designing high-repetition rate sources required for optical communications and spectroscopy. Theoretically, understanding chaotic regimes within soliton formation and switching unlocks new pathways to explore complex nonlinear dynamics in integrated photonic systems.

The deterministic procedure for generating soliton lattices might pave the way for novel on-chip comb sources optimized for precision applications in coherent communication, spectrometer calibration, and potentially astrophysical observations. Additionally, linking soliton dynamics with chaos theory is likely to inform future designs of microresonator devices that leverage controlled instability for high-efficiency outputs.

Conclusions

Overall, the paper presents significant advances in controlling the dynamics of soliton formations within microresonators, specifically through managing chaotic regimes and deterministic generation protocols. This work creates opportunities not only for practical applications in photonic technology but also for advancing our theoretical understanding of nonlinear dynamical systems in optical physics. As researchers further explore these domains, the insights from this paper will likely propel innovations in both fundamental research and applied photonic technologies.