Advanced phase retrieval for dispersion scan: a comparative study

TL;DR

This paper compares different algorithms for dispersion scan phase retrieval, demonstrating that differential evolution significantly improves accuracy and speed, enabling near-perfect phase recovery of complex ultrashort pulses even under challenging conditions.

Contribution

The study introduces and evaluates three strategies for dispersion scan phase retrieval, highlighting the superior performance of differential evolution in complex pulse scenarios.

Findings

Differential evolution outperforms other methods in accuracy and speed.

All tested strategies improve retrieval precision and convergence.

Near-perfect phase retrieval achieved within ten seconds, even with noise.

Abstract

Dispersion scan is a self-referenced measurement technique for ultrashort pulses. Similar to frequency-resolved optical gating, the dispersion scan technique records the dependence of nonlinearly generated spectra as a function of a parameter. For the two mentioned techniques, these parameters are the delay and the dispersion, respectively. While dispersion scan seems to offer a number of potential advantages over other characterization methods, in particular for measuring few-cycle pulses, retrieval of the spectral phase from the measured traces has so far mostly relied on the Nelder-Mead algorithm, which has a tendency of stagnation in a local minimum and may produce ghost satellites in the retrieval of pulses with complex spectra. We evaluate three different strategies to overcome these retrieval problems, namely regularization, use of a generalized-projections algorithm, and an evolutionary retrieval algorithm. While all these measures are found to improve the precision and convergence of dispersion scan retrieval, differential evolution is found to provide the best performance, enabling the near-perfect retrieval of the phase of complex supercontinuum pulses within less than ten seconds, even in the presence of strong detection noise and limited phase-matching bandwidth of the nonlinear process.