Chaotic Internal Dynamics of Dissipative Optical Soliton Molecules

Abstract

When a laser cavity supports the propagation of several ultrashort pulses, these pulses can form compact bound states called soliton molecules. Soliton molecules are fascinating objects of nonlinear science, presenting striking analogies with their matter molecule counterparts. The relative timing and phase between the copropagating pulses are the most salient internal degrees of freedom of the soliton molecule. The soliton pair, composed of two identical pulses, constitutes the chief soliton molecule of fundamental interest. Its two major internal degrees of freedom allow self-oscillating soliton molecules, which have been recurrently observed. However, despite theoretical predictions, the low-dimensional chaotic dynamics of a soliton-pair molecule remain elusive. This article reports the observation of chaotic soliton-pair molecules within an ultrafast fiber laser by means of a direct measurement of the relative optical pulse separation with sub-femtosecond precision in real time. Moreover, it demonstrates an all-optical control of the chaotic dynamics followed by the soliton molecule by injection of a modulated optical signal that resynchronizes the internal periodic vibration of the soliton molecule. The fast error-free switching between ordered and chaotic soliton molecules enabled by pump current sweeping and external injection highlights the potential prospects of all-optical logic gates and chaotic communication using soliton molecules.