[Paper Review] Spectral pulsations of dissipative solitons in ultrafast fiber lasers: period doubling and beyond

Zhiqiang Wang, Aurélien Coillet+3 more|arXiv (Cornell University)|Apr 28, 2022

Advanced Fiber Laser Technologies8 citations

TL;DR

This paper investigates spectral pulsations in ultrafast fiber lasers driven by dissipative solitons, revealing period-doubling bifurcations and complex instabilities through real-time spectral characterization. It demonstrates that these pulsations arise from intertwined bifurcations, including frequency locking to round-trip harmonics, with experimental and numerical evidence confirming the universality of period-doubling dynamics in both anomalous and normal dispersion regimes.

ABSTRACT

Period doubling is a universal bifurcation of central importance in all disciplines of nonlinear science, which generally signals the existence of chaotic dynamics in the vicinity of the system parameters. Although observed in diverse ultrafast laser configurations, there is still no consensus on its physical origin. The observations also include other types of pulsating dissipative solitons, with either short or long periods. Real time spectral characterization allows to investigate optical spectral oscillations, whose features reveal the intracavity dynamics leading to instabilities. Following a contextual review, this article presents a variety of period doubling dynamics manifesting in the spectral domain of dissipative solitons. These dynamics are obtained with ultrafast fiber lasers featuring either anomalous or normal dispersion. It reveals a sequence of period doubling bifurcations and instabilities within transient dynamics, unveiling intertwined bifurcations and the entrainment of new pulsating frequencies. The oscillating frequencies tend to lock to the integral of roundtrip numbers as well as coexist with period doubling, demonstrating new combinations of the period doubling bifurcation with other bifurcations. These experimental findings are confirmed by numerical simulations, emphasizing both the universality of the period doubling bifurcations and their potentially highly complicated manifestations within ultrafast laser systems.

Motivation & Objective

• To understand the physical origin of period-doubling bifurcations in dissipative solitons within ultrafast fiber lasers.
• To characterize spectral oscillations and transient dynamics leading to instabilities in both anomalous and normal dispersion fiber lasers.
• To identify complex bifurcation structures, including entrainment of new pulsating frequencies and locking to round-trip harmonics.
• To validate experimental observations with numerical simulations, demonstrating the universality of period-doubling phenomena.
• To reveal new combinations of period-doubling bifurcations with other dynamical instabilities in dissipative soliton systems.

Proposed method

• Real-time spectral characterization using advanced optical sampling techniques to resolve ultrafast spectral oscillations in dissipative solitons.
• Experimental implementation of ultrafast fiber lasers with both anomalous and normal dispersion configurations.
• Numerical simulations based on the complex Ginzburg-Landau equation to model and reproduce observed pulsating dynamics.
• Analysis of temporal and spectral evolution to identify bifurcation sequences and frequency locking phenomena.
• Use of round-trip number integration to detect synchronization between pulsation frequencies and cavity round-trip cycles.
• Contextual review of period-doubling bifurcations in nonlinear systems, linking to observed optical dynamics.

Experimental results

Research questions

• RQ1 What causes period-doubling bifurcations in dissipative solitons of ultrafast fiber lasers?
• RQ2 How do spectral pulsations evolve during transient dynamics, and what bifurcation sequences are involved?
• RQ3 To what extent do pulsating frequencies lock to integer multiples of the cavity round-trip frequency?
• RQ4 What role do intertwined bifurcations play in the emergence of complex pulsating dynamics?
• RQ5 How do normal and anomalous dispersion regimes compare in supporting period-doubling and spectral pulsation phenomena?

Key findings

• Period-doubling bifurcations are observed in both anomalous and normal dispersion ultrafast fiber lasers, confirming their universality in dissipative soliton systems.
• Spectral pulsations exhibit a sequence of period-doubling events, indicating the onset of chaotic dynamics near critical parameter regimes.
• New pulsating frequencies emerge and become entrained with the cavity round-trip frequency, demonstrating harmonic locking.
• The system displays intertwined bifurcations, where period doubling coexists with other instability mechanisms.
• Numerical simulations reproduce experimental observations, validating the theoretical framework and highlighting the complexity of nonlinear dynamics.
• Real-time spectral measurements reveal that spectral oscillations are direct indicators of intracavity instability and bifurcation pathways.