Based on the spin flip model, four schemes for the polarization switching of the 1550 nm vertical cavity surface emitting laser are studied by using numerical simulation, which are free running laser orthogonal injection free running laser, free running laser orthogonal injection polarization maintaining optical feedback laser, polarization maintaining optical feedback laser orthogonal injection free running laser, and polarization maintaining optical feedback laser orthogonal injection polarization maintaining optical laser. We can draw three conclusions from the numerical results. Firstly, changing the feedback strength can make the polarization switching point of the injection intensity in the different regular movements when the normalized injection current is small. The injection intensity of the polarization switching point increases with the increase of the feedback strength for the free running laser orthogonal injection polarization maintaining optical feedback laser; the injection intensity of the polarization switching point decreases with the increase of the feedback strength for the polarization maintaining optical feedback laser orthogonal injection free running laser; the injection intensity of the polarization switching point is nonlinear and fluctuates with the increase of the feedback strength for the polarization maintaining optical feedback laser orthogonal injection polarization maintaining optical laser. The reason is that the non dominant X polarization component cannot go up when the normalized injection current is small, then, as the feedback intensity increases, the difference between the two polarization components will be increased. Secondly, when the normalized injection current is large, changing the feedback intensity can make the polarization switching point of the injection intensity in the irregular movement. The reason is that the non dominant X polarization component can go up when the normalized injection current increases up to a certain value, which can form the significant nonlinear wave together with the dominant Y polarization component. Thirdly, changing the frequency detuning can make the polarization switching point of the injection intensity in the same regular movement. The injection strength required for the occurrence of polarization switching point first decreases and then increases for the four schemes, when the frequency detuning is from approximately -60 GHz to the minimum, presenting the symmetrical distribution of V type with -60 GHz as the axis. The same regular movement of the polarization switching point of the injection intensity is not changed with the change of the normalized injection current.
