Towards 'smart lasers': self-optimisation of an ultrafast pulse source using a genetic algorithm.

R I Woodward,E J R Kelleher

doi:10.1038/srep37616

Abstract

Short-pulse fibre lasers are a complex dynamical system possessing a broad space of operating states that can be accessed through control of cavity parameters. Determination of target regimes is a multi-parameter global optimisation problem. Here, we report the implementation of a genetic algorithm to intelligently locate optimum parameters for stable single-pulse mode- locking in a Figure-8 fibre laser, and fully automate the system turn-on procedure. Stable ultrashort pulses are repeatably achieved by employing a compound fitness function that monitors both temporal and spectral output properties of the laser. Our method of encoding photonics expertise into an algorithm and applying machine-learning principles paves the way to self-optimising ‘smart’ optical technologies.

Highlights

Optimisation can be efficiently implemented using machine learning principles
The compound fitness function-based Genetic algorithms (GAs) is applied to the Figure-8 laser, initialised from a unique, randomised set of polarisation parameters, and a pump current corresponding to a sub-threshold power
We have demonstrated a self-optimising ultrafast Figure-8 fibre laser by employing a compound fitness function based genetic algorithm

Summary

Introduction

Optimisation can be efficiently implemented using machine learning principles. Genetic algorithms (GAs) are ideal for this task, applying concepts of natural selection from evolutionary biology to intelligently search for optimum parameters[16]. The application of GAs for extremum seeking in laser mode-locking was recently proposed theoretically[21,22], and a basic implementation utilizing a singular fitness function to locate self-starting regimes in an NPE-mode-locked fibre laser was demonstrated[23,24]. For a fixed pump power, the nonlinear transmission curve of the NALM is governed by the angle of the four waveplates, adjustment of which sweeps the laser operating regime through a wide range of states To illustrate this variation, we represent a two-dimensional slice of the four-dimensional polarisation space: the pump power is held constant while two quarter waveplates are successively swept through all possible angles in 4.5 degree (0.025π rad) steps (Fig. 2).

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Results

Conclusion