Abstract

Ultra-short pulses with durations that can reach the few femto-seconds regime are mostly obtained by passive mode-locked (PML) lasers [1]. Active mode-locking (AML) is another way to achieve short pulses, generally with longer durations compared to PML. In the theory of active-mode-locking, the modulation causes every axial mode to inject power into adjacent modes [1]. From a physical perspective, this process can be viewed as an effective mode-mode interaction, resembling the spin-spin interaction in magnetic systems. A mathematical analogy can be drawn [2,3] between AML lasers and magnetic spin systems in the spherical model [4], where the axial modes of the laser are mapped to the magnetic spins. In this theory, the optical noise takes the role of temperature and the pulse amplitude is mapped to the magnetic spin.

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