Refining the modelling of mode-locked fiber lasers

Abstract

Numerical modelling plays an increasingly important role in the development of ultrafast fiber lasers, and there is a continued interest into developing physically realistic models to describe experimental observations. Modelling serves two predominant functions: it (i) provides essential insights into the underlying physics and operation dynamics of existing oscillators and (ii) allows for the effortless exploration of parameter regimes for new laser architectures. In order to successfully perform these tasks it is essential that the used models capture the rich dynamics associated with broadband nonlinear pulse propagation. However, the majority of the models used in the simulation of mode-locked fiber laser neglect vital terms in the used pulse propagation equations and/or resort to approximate functional dependencies for the gain dynamics or the mode-locker. In this work we report on first principles modelling of mode-locked fiber lasers. Our simulations combine full generalized envelope equations commonly encountered in modelling broadband supercontinuum generation, with gain dynamics directly evaluated from rate equations. Moreover, we consider fiber lasers mode-locked with nonlinear (amplifying) loop mirrors (NALMs) so that we are able to rigorously model the all-fiber mode-locker without approximations. As a matter of fact, comparison of simulation results with experiments performed with all-normal-dispersion (ANDi) oscillators mode-locked with a NALM shows astonishing agreement.