Polarization switching and synchronization of mutually coupled vertical-cavity surface-emitting semiconductor lasers

Polarization switching (PS) dynamics and synchronizationperformances of two mutually coupled vertical-cavitysurface-emitting lasers (VCSELs) are studied theoretically inthis paper. A group of dimensionless rate equations is derivedto describe our model. While analysing the PS characteristics,we focus on the effects of coupling rate and frequency detuningregarding different mutual injection types. The results indicatethat the x-mode injection defers the occurrence of PS, whilethe y-mode injection leads the PS to occur at a lower current.Strong enough polarization-selective injection can suppress thePS. Moreover, if frequency detuning is considered, the effectsof polarization-selective mutual injection will be weakened. Toevaluate the synchronization performance, the correlationcoefficients and output dynamics of VCSELs with both pure modeand mixed mode polarizations are given. It is found thatperformance of complete synchronization is sensitive to thefrequency mismatch but it is little affected by mixed modepolarizations, which is opposite to the case ofinjection-locking synchronization.