Synchronization of the internal dynamics of optical soliton molecules

Compact bound states of light pulses in ultrafast lasers are known as optical soliton molecules. They constitute nonlinear superstructures choice to investigate complex dynamical phenomena that manifest similarly a wide range systems. Akin matter molecules, molecules can feature vibrational motions between their internal constituents. However, these vibrations intrinsically nonlinear, with oscillation frequencies sensitive system parameters. Therefore, vibrating present an opportunity for control. We here the precise control through universal mechanism synchronization master and slave oscillators. Self-oscillating prepared within passively mode-locked fiber laser. experimentally demonstrate injection oscillator signal. Direct observation process is enabled by balanced cross-correlation detection, technique allowing real-time detection intramolecular separation femtosecond temporal resolution. show efficient sub-harmonic, fundamental, super-harmonic synchronization, forming pattern Arnold tongues respect strength. Numerical simulations support experimental observations. By retrieving features, role molecule chief importance further highlighted.