Real-Time Observation of the Buildup of Soliton Molecules

Abstract

Real-time spectroscopy access to ultrafast fiber lasers opens new opportunities for exploring complex soliton interaction dynamics. Here, we have reported the first observation, to the best of our knowledge, of the entire buildup process of soliton molecules (SMs) in a mode-locked laser. We have observed that the birth dynamics of a stable SM experiences five different stages, i.e., the raised relaxation oscillation (RO) stage, beating dynamics stage, transient single pulse stage, transient bound state, and finally the stable bound state. We have discovered that the evolution of pulses in the raised RO stage follows a law that only the strongest one can ultimately survive and, meanwhile, the pulses periodically appear at the same temporal positions for all lasing spikes during the same RO stage (named as memory ability) but they lose such ability between different RO stages. Moreover, we have found that the buildup dynamics of SMs is quite sensitive to both the polarization state of intracavity light and the fluctuation of pump power. These results provide new perspectives into the ultrafast transient process in mode-locked lasers and the dynamics of complex nonlinear systems.

Revealing the Buildup Dynamics of Harmonic Mode‐Locking States in Ultrafast Lasers

“…Figure a illustrates the Fourier transform of each single‐shot spectrum in Figure b, corresponding to a field autocorrelation of the momentary pulses, which traces the evolution of temporal separation between pulses . Figures b and 5c are enlargements of the A and B regions in Figure a, respectively.…”

“…Ultrafast lasers with high repetition rate have many potential applications in multiple areas such as optical telecommunications, frequency metrology, high‐speed optical sampling, and data storage . Usually, fiber lasers have a fundamental repetition rate of tens to hundreds of MHz due to the difficulty of shortening the laser cavity . To increase the pulse repetition rate of fiber lasers, a less technically challenging and more convenient way is the harmonic mode‐locking (HML) scheme, where multiple pulses are evenly spaced in the cavity .…”

Soliton molecules and asymmetric solitons in three fifth order systems via velocity resonance

“…In summary, soliton molecules can be found not only in the optical systems [2,4] but also in fluid systems, which may be applied for the oceanic surface and internal waves [29,30], plasma waves [35], electromagnetic waves in discrete transmission lines [36] and so on. The fluid model (1) is integrable only in three special cases involving the fifth order KdV equation, the SK equation and the KK equation.…”

“…Soliton molecules and bound states of solitons have been observed experimentally in optics [1][2][3][4] and predicted numerically in Bose-Einstein condensates [5]. On the other hand, solitons play a very important role in various modern scientific fields including fluids [6], plasmas [7], fibers [8], optics [9], complex networks [10], quantum field theory [11], gravity [12], Bose-Einstein condensates [13], atmospheric and oceanic dynamics [14] and so on.…”

Real-Time Observation of the Regime Transition Dynamics of Mode-Locked Fiber Lasers

“…Through a dispersive medium, the TS-DFT builds up a mapping from the spectrum to the temporal domain pulse and a realtime optical spectrum analysis can be performed by combining the TS-DFT with a real-time oscilloscope 13 . The TS-DFT provides endless possibilities for comprehension of ultrafast physical phenomena, including optical rogue waves [14][15][16] , soliton explosions 17,18 , mode-locking build-up processes [19][20][21] and sophisticated soliton dynamics [22][23][24][25] . Herink et al successively resolved the modelocking build-up process 19 and soliton molecule formation process 22 of a Kerr-lens Ti: sapphire laser.…”