  Defects due to growth fluctuations in broad-area semiconductor lasers induce
pinning and frequency shifts of spatial laser solitons. The effects of defects
on the interaction of two solitons are considered in lasers with
frequency-selective feedback both theoretically and experimentally. We
demonstrate frequency and phase synchronization of paired laser solitons as
their detuning is varied. In both theory and experiment the locking behavior is
well described by the Adler model for the synchronization of coupled
oscillators.
