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Dynamical study and bifurcation analysis of polarization switching in vertical-cavity surface-emitting lasers

One of the most intriguing aspects of Vertical-Cavity Surface-Emitting Lasers (VCSEL's) lies in their polarization behavior, which differs from the one of edge-emitting lasers due to the lack of a dominating polarization selection mechanism in the quasi cylindrically symmetric structure. A number of different explanations of this polarization behavior, and especially of the observed polarization switching, have been put forward. A first model is of a thermal nature and attributes the switching to the shift (caused by the current heating) of the material gain spectral profile relative to the cavity resonances for the two frequency-split polarization modes [1J. An alternative thermal explanation focuses on the effects of a thermally induced waveguide occurring in the VCSEL (the so-called thermal lensing effect) and the subsequent competition of the modal gains of the two orthogonal polarization modes coexisting in the slightly anisotropic laser resonator [2].