Using spin-flip model (SFM) of vertical-cavity surface-emitting lasers (VCSELs) subject to polarized injection, it is
found that reducing the spin relaxation, or increasing the birefringence and pumping terms, can increase elliptically
polarized injection locking (EPIL) stability for the slave VCSEL. The nonlinear dynamic is investigated in optically
injected VCSELs with numerical simulation techniques for six fundamental VCSEL rate equations. A novel
phenomenon as quasi stability which affects the EPIL is analyzed.