  We present a phase retrieval algorithm for dispersion scan (d-scan), inspired
by ptychography, which is capable of characterizing multiple
mutually-incoherent ultrafast pulses (or modes) in a pulse train simultaneously
from a single d-scan trace. In addition, a form of Newton's method is employed
as a solution to the square root problem commonly encountered in second
harmonic pulse measurement techniques. Simulated and experimental phase
retrievals of both single-mode and multi-mode d-scan traces are shown to
demonstrate the accuracy and robustness of the algorithm.
