Numerical model of hybrid mode-locked Tm-doped all-fibre laser

Aleksandr Donodin,Daniil Batov,Vladimir Lazarev,Mikhail Tarabrin,Dmitrii Vlasov,Vasilii Voropaev,Mikhail Likhachev,Aleksandr Khegai

doi:10.1038/s41598-020-74194-7

Abstract

Ultrafast Tm-doped fibre lasers have been actively studied for the last decade due to their potential applications in precise mid-IR spectroscopy, LIDARs, material processing and more. The majority of research papers is devoted to the comparison between a numerical modelling and experimental results; however, little attention is being paid to the comprehensive description of the mathematical models and parameters of the active and passive components forming cavities of Tm-doped all-fibre lasers. Thus, here we report a numerical model of a stretched-pulsed Tm-doped fibre laser with hybrid mode-locking and compare it with experimental results. The key feature of the developed numerical model is employment of the experimentally measured dispersion coefficients and optimisation of some model parameters, such as the bandwidth of the spectral filter spectral filtering and the saturation power of the active fibre, for a conformity with the experiment. The developed laser emits 331.7 fs pulses with a 23.8 MHz repetition rate, 6 mW of average power, 0.25 nJ of pulse energy, and a 21.66 nm spectral bandwidth at a peak wavelength of 1899.5 nm. The numerical model characteristics coincide with experimentally achieved spectral width, pulse duration, and average power with inaccuracy of 4.7%, 5.4%, and 22.9%, respectively. Moreover, in the discussion of the work the main possible reasons influencing this inaccuracy are highlighted. Elimination of those factors might allow to increase accuracy even more. We show that numerical model has a good agreement with the experiment and can be used for development of ultrafast Tm-doped fibre laser systems.

Highlights

Ultrafast Tm-doped fibre lasers have been actively studied for the last decade due to their potential applications in precise mid-IR spectroscopy, LIDARs, material processing and more
Despite the comprehensive analysis of generation regimes and the comparison between the numerical modelling and the experimental results, little attention is being paid to the detailed description of the used mathematical model and the parameters of active and passive components of cavity (GVDs of fibres, nonlinear coefficients of fibres, spectral characteristics of the laser cavity components, parameters of the active fibres, parameters of saturable absorbers (SA), etc.)
The increase of grid points to 213 in time domain with the same bandwidth of the time window led to a relative change of pulse and spectral width less than 0.04%, while the computation time was increased by 3.7 times

Summary

Introduction

Ultrafast Tm-doped fibre lasers have been actively studied for the last decade due to their potential applications in precise mid-IR spectroscopy, LIDARs, material processing and more. Various numerical models based on different modifications of the nonlinear Schrödinger equation for simulation of intracavity pulse propagation were proposed[30,31,32,33] and implemented[34,35,36,37] to study ultrafast lasers during last three decades The majority of these papers were focused on studying of Er- and Yb-doped fibre lasers because of the current relative maturity of these laser sources. Despite the comprehensive analysis of generation regimes and the comparison between the numerical modelling and the experimental results, little attention is being paid to the detailed description of the used mathematical model and the parameters of active and passive components of cavity (GVDs of fibres, nonlinear coefficients of fibres, spectral characteristics of the laser cavity components, parameters of the active fibres, parameters of SAs, etc.)

Findings

Discussion

Conclusion