Modelling thermal effects on polarisation switching in surface-emitting semiconductor lasers

Abstract

A phenomenological model has been developed that describes the induced anisotropy of the vertical-cavity surface-emitting laser (VCSEL) gain for the single-mode mode in the form of a second-order polynomial with respect to the degrees of density of the injection current, where the decomposition coefficients are implicit functions of temperature. The model is based on the analysis of data from theoretical and experimental studies of the dynamics of thermal processes in VCSEL. From the general view of the dependencies, it follows that in single-mode operation, a VCSEL cannot have more than two polarisation switching points, and of different types. The performance of the model is demonstrated on the basis of a qualitative analysis of previously published series of experimental data on temperature dependencies of the position of polarisation switching points. For short-wave emitters, such dependencies are monotonic and can be easily described by the relative shift of the curves that determine the anisotropy of the gain for orthogonally polarised modes. For longavelength VCSELs, the data for which have been published in the literature, the situation turns out to be much more complicated: not only the relative location of the curves changes, but also their «curvature», which is mainly associated with the quadratic term. At the same time, it turned out to be possible to explain the almost constant position of one of the points of polarisation switching.