Current driven switching between two orthogonal linear polarizations in the fundamental mode of VCSELs is the object of intensive experimental and theoretical work. We developed a model based on the experimental evidence that the gain/loss difference between the two modes is an important factor in polarization switching. We analytically and numerically study a nearly-degenerate two-mode intensity rate equation model. The gain coefficients we use are current dependent and gain saturation with increasing optical power is also taken into account. Two types of stationary solutions emerge: pure-mode solutions (one mode lases) and mixed mode solutions (both modes lase). Stability analysis shows that when the gains equalize, switching between the two pure-mode solutions occurs. The nonlinear gain induces a region of bistability around the switching point. Taking into account the different time scales present in the model and using asymptotic techniques, we can further reduce the model to a single dynamical equation, which can be solved analytically. Stochastic effects (e.g. due to spontaneous emission) can be incorporated in this 1D Langevin-type equation. This allows us to explain the mode hopping in terms of a First Passage Time over the potential barrier in a double potential well.

Date Published: 9 July 2001
PDF: 12 pages
Proc. SPIE 4283, Physics and Simulation of Optoelectronic Devices IX, (9 July 2001); doi: 10.1117/12.432575

Published in SPIE Proceedings Vol. 4283:
Physics and Simulation of Optoelectronic Devices IX
Yasuhiko Arakawa; Peter Blood; Marek Osinski, Editor(s)