Robust orthogonal parameterization of evolution strategy for adaptive laser pulse shaping

Aliakbar Jafarpour,Rianne De Jong,Peter Van Der Walle,Janne Savolainen,Jacob Middag,Jennifer L Herek,Di Yang,Daan P Sprünken

doi:10.1364/oe.17.011986

Aliakbar Jafarpour, Rianne De Jong + Show 6 more

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https://doi.org/10.1364/oe.17.011986

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Abstract

Many spectroscopic applications of femtosecond laser pulses require properly-shaped spectral phase profiles. The optimal phase profile can be programmed on the pulse by adaptive pulse shaping. A promising optimization algorithm for such adaptive experiments is evolution strategy (ES). Here, we report a four fold increase in the rate of convergence and ten percent increase in the final yield of the optimization, compared to the direct parameterization approach, by using a new version of ES in combination with Legendre polynomials and frequency-resolved detection. Such a fast learning rate is of paramount importance in spectroscopy for reducing the artifacts of laser drift, optical degradation, and precipitation.

Highlights

Femtosecond laser pulses are widely used in spectroscopy for monitoring or controlling electronic, excitonic, plasmonic, and vibrational transitions
To test and verify the applicability of aforementioned parameterizations in practical laser pulse shaping applications, we use the output of a femtosecond laser amplifier (Legend Elite, Coherent Inc.) generating pulses with a full-width half maximum (FWHM) bandwidth of 35nm centered at 800nm
We have successfully reduced the number of generations required for the CMA-evolution strategy (ES) algorithm to converge to an optimal solution of the second harmonic generation (SHG) optimization problem

Summary

Introduction

Femtosecond laser pulses are widely used in spectroscopy for monitoring or controlling electronic, excitonic, plasmonic, and vibrational transitions. Finding a laser pulse to optimize an ultrafast physical or chemical process [1] is a classical problem in optimal control theory [2,3]. Once the dynamics (Hamiltonian) of a system are known, the control problem can be formulated. Analytical or even numerical solutions are only available for simple systems. An adaptive scheme is used to find the optimal laser pulse [4,5,6,7]. A pulse shaper tailors the properties of the input pulse, and an optimization algorithm determines the pulse shape in accordance with a feedback signal from the optical process, and this process is iterated (Fig. 1)

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