Research Article

Real-time spectral interferometry probes the internal dynamics of femtosecond soliton molecules

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Science  07 Apr 2017:
Vol. 356, Issue 6333, pp. 50-54
DOI: 10.1126/science.aal5326

Probing the interaction of solitons

As a pulse of light propagates through a medium, scattering and dispersion processes usually result in the pulse diffusing. However, under certain circumstances, the dispersion processes can be balanced by nonlinearities to produce localized structures known as solitons or optical bullets. Herink et al. used spectral interferometry to image and track the formation of soliton complexes as they propagated in a laser cavity. Real-time access to the formation processes and complex interaction dynamics could help in modeling other nonlinear systems.

Science, this issue p. 50


Solitons, particle-like excitations ubiquitous in many fields of physics, have been shown to exhibit bound states akin to molecules. The formation of such temporal soliton bound states and their internal dynamics have escaped direct experimental observation. By means of an emerging time-stretch technique, we resolve the evolution of femtosecond soliton molecules in the cavity of a few-cycle mode-locked laser. We track two- and three-soliton bound states over hundreds of thousands of consecutive cavity roundtrips, identifying fixed points and periodic and aperiodic molecular orbits. A class of trajectories acquires a path-dependent geometrical phase, implying that its dynamics may be topologically protected. These findings highlight the importance of real-time detection in resolving interactions in complex nonlinear systems, including the dynamics of soliton bound states, breathers, and rogue waves.

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