Square-wave switching in vertical-cavity surface-emitting lasers with polarization-rotated optical feedback: Experiments and simulations

摘要

We study experimentally the dynamics of vertical-cavity surface-emitting lasers (VCSELs) with polarizationrotatedn(PR) optical feedback, such that the natural lasing polarization of a VCSEL is rotated by 90 deg and thennis reinjected into the laser. We observe noisy, square-wave-like polarization switchings with periodicity slightlynlonger than twice the delay time, which degrade to (or alternate with) bursts of irregular oscillations. We presentnresults of simulations that are in good agreement with the observations. The simulations demonstrate that closento threshold the regular switching is very sensitive to noise, while well above threshold is less affected by thennoise strength. The frequency splitting between the two polarizations plays a key role in the switching regularity,nand we identify wide parameter regions where deterministic and robust switching can be observed.