Pulse growth dynamics in laser mode locking

TL;DR

This paper investigates the nonlinear dynamics of pulse formation in mode locked lasers, revealing a multi-stage growth process characterized by slow initial energy cascade, rapid nonlinear growth, and eventual stabilization constrained by gain bandwidth.

Contribution

It provides a theoretical and numerical analysis of pulse growth dynamics in mode locked lasers, highlighting the stages and mechanisms involved in pulse formation.

Findings

Pulse growth involves energy cascade from low to high modes.

Peak power approaches a finite-time singularity.

Gain bandwidth saturation limits pulse peak power.

Abstract

We analyze theoretically and numerically the nonlinear process of pulse formation in mode locked lasers starting from a perturbation of a continuous wave. Focusing on weak to moderate dispersion systems, we show that pulse growth is initially slow, dominated by a cascade of energy from low to high axial modes, followed by fast strongly nonlinear growth and finally relaxation to the stable pulse waveform. The pulse grows initially by condensing a fixed amount of energy into a decreasing time interval, with peak power growing toward a finite-time singularity that is checked when the gain bandwidth is saturated by the pulse.