The effect of nonlinear gain on the characteristics of an optically injected VCSEL and cavity solitons
Using the Lagrange method to fit the curve of maximum gain as a function of carrier density for an active region consisting of an AlGaAs/GaAs layers sandwiched between DBR layers, it is found that the curve is better approximated assuming a quadratic dependence on the carrier density. By summarizing all of the calculations into a nonlinear gain coefficient parameter, \(\beta \), in the Maxwell–Bloch equations we numerically studied the effect of nonlinear gain on the characteristics of the VCSEL and also on the cavity solitons (CSs) forming in such a device. Particularly, it is shown that with nonlinear gain a wider locked region can be achieved along with enhanced sustained relaxation oscillation amplitude. The switching on/off time of CSs is modified and there appears a considerable enhancement in their efficiency and contrast.
KeywordsBistability Relaxation oscillation VCSEL Semiconductor gain Cavity soliton
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