  A novel algorithm for the ultrashort laser pulse characterization method of
interferometric frequency-resolved optical gating (iFROG) is presented. Based
on a genetic method, namely differential evolution, the algorithm can exploit
all available information of an iFROG measurement to retrieve the complex
electric field of a pulse. The retrieval is subjected to a series of numerical
tests to prove robustness of the algorithm against experimental artifacts and
noise. These tests show that the integrated error-correction mechanisms of the
iFROG method can be successfully used to remove the effect from timing errors
and spectrally varying efficiency in the detection. Moreover, the accuracy and
noise resilience of the new algorithm are shown to outperform retrieval based
on the generalized projections algorithm, which is widely used as the standard
method in FROG retrieval. The differential evolution algorithm is further
validated with experimental data, measured with unamplified three-cycle pulses
from a mode-locked Ti:sapphire laser. Additionally introducing group delay
dispersion in the beam path, the retrieval results show excellent agreement
with independent measurements with a commercial pulse measurement device based
on spectral phase interferometry for direct electric-field retrieval. Further
experimental tests with strongly attenuated pulses indicate resilience of
differential evolution based retrieval against massive measurement noise.
