Analysis of short pulse generation from excited state of InAs-InP(113)B quantum dot laser based on multi-population rate equations

In this study, gain-switching characteristics of InAs-InP(113)B quantum dot laser based on multi-mode rate equations are investigated for the first time by applying an external Gaussian pulse beam into the excited state to obtain short pulses. The rate equations including nonlinear gain are solved for direct relaxation model by 4(th) order Runga-Kutta method. The obtained results demonstrated that width of gain-switching output pulses are long due to dominant effect of ground state photons having long width without optical beam. Furthermore, pulse width increases with the increasing the peak injection current was observed. However, it was found that since excited state photons have narrow width compared to that of ground state, width of output pulses decreases giving a pulse width of around 25 ps owing to dominant effect of excited state with the applying optic beam into excited state. Our results also indicated that differential-gain of excited and groundstates decreases with the increasing of the homogeneous and inhomogeneous broadenings.