Dynamics of vertical-cavity surface emitting lasers under selective polarization rotated feedback and coupling

We study numerically the dynamics of VCSELs with polarization-rotated (PR) optical feedback or coupling, such that the natural lasing polarization of a VCSEL is rotated by 90 degrees and then is either feed back into the same laser, or is injected into another laser. In the latter case the coupling is symmetric and each laser receives PR injection. In the feedback scheme, we find stationary dynamics consisting on noisy, square-wave-like polarization switching with periodicity slightly longer than twice the feedback delay time, that degrade to (or alternate with) bursts of irregular and faster oscillations. In the coupling scheme, the square-waves are transient and decay towards one of the various possible stationary states. The influence of various model parameters on the duration of the stochastic transient time and on the lasers´ dynamics in the stationary state is investigated.