Experimental Determination And Theoretical Study Of Key Parameters In The Spin-flip Model Of 1550 Nm Vertical-cavity Surfaceemitting Laser

Semiconductor Lasers(SLs)have been developed fast as the most important light source in the field of optical communication.Vertical-Cavity Surface-Emitting Lasers(VCSELs)have become a focus because of some advantages such as small volume,low threshold current,high modulation efficiency,single-longitudinal mode output and so on.Recently,the making craft of short-wavelength VCSELs is relatively mature and performance is relatively stable,so it has been greatly used in the field of short-range and medium-range distance optical communication;the making craft of long-wavelength VCSELs have been gradually perfected,especially the 1550 nm VCSELs have immeasurable potential and applied value in the long distance and large capacity optical fiber communication mains because its wavelength locates at the zero dispersion and low loss window.Hence,the experimental and theoretical research of 1550 nm VCSELs have very important significance.Spin-Flip Model(SFM)is a mostly used approach to analyze the nonlinear dynamics of 1550 nm VCSELs in theoretical research.Under the given condition of bias current,it is necessary to give the numerical values of the key parameters in the model in order to obtain the time series of two polarization components by numerically solving,so as to analyze the dynamic characteristics.Therefore,the values of these parameters have greater impact for the dynamic characteristics of 1550 nm VCSELs.Hence,it is the key to correctly predict the dynamic characteristics of 1550 nm VCSELs that how to accurately determine the values of these parameters.In this paper,based on experimentally measured dynamical characteristics of a 1550 nm VCSEL under free running and parallel polarized optical injection,some key parameters(the field decay rate k,the total carrier decay rate ?N,linewidth enhancement factor ?,the active medium birefringence rate ?p,the spin relaxation rate ?s,the active medium linear dispersion rate ?a)are estimated.Through experimentally measuring the noise spectrum of the laser,the relaxation oscillation frequency and the damping rate of the relaxation oscillations are calculated,and the photon lifetime can be preliminary estimated.After further amending the photon lifetime by considering the effect of the gain saturation on the damping rate of the relaxation oscillations,the value of k is determined.Based on the function relation between the laser relaxation oscillation frequency and the electrical pumping,the value of ?N is obtained.By experimentally acquiring the dynamical distribution mapping of the laser under parallel polarized optical injection,the minimum Hopf bifurcation point of the Hopf bifurcation curve can be found,and then the value of ? is roughly estimated.According to the frequency difference between the two polarization components of the laser in the measured optical spectrum,the value of ?p can be calculated.The value of ?s is obtained by using the relationship between ?s and ?p.On the basis of the above determined parameter values,the value of ?a can be specified by numerically simulating the optical spectrum of the laser and comparing with experimentally obtained results.Moreover,by comparing the experimentally measured dynamical mapping of optical injection 1550 nm VCSEL with corresponding dynamical mapping simulated on the basis of the above mentioned parameters,the value of ? is rectified.In order to further prove that the six key parameters are correct,we used the key parameters to numerically simulate the enhancement of chaotic signal bandwidth in 1550 nm VCSEL induced by polarized optical injection,the results show that the simulated results agree with the experimental observations.Finally,above results indicate that the six key parameters are correct and the measured method is reasonable.