Periodic Entrainment of Power Dropouts in Mutually Coupled Semiconductor Lasers

We examine the effect of current modulation in the irregular dropout dynamics exhibited by
two mutually coupled semiconductor lasers. Our experimental results show that a weak periodic
modulation in the injection current of one of the lasers entrains the power dropouts in a very efficient
way. It is also observed that the laser with the highest frequency leads the dynamics independently
of which laser is modulated. As a result, the entrainment is anticipative when modulation is applied
to the laser with lowest frequency. Numerical simulations of a model based on delay-coupled rate
equations successfully reproduce the observed behavior.