| Abstract: | Large-signal modulation capability,as an important performance indicator,is directly related to the high-speed optical communication technology involved.We experimentally and theoretically investigate the large-signal modulation characteristics of the simultaneous ground-state(GS) and the excited-state(ES) lasing in InAs/GaAs quantum dot laser diodes.The large-signal modulation capability of total light intensity in the transition regime from GS lasing to two-state lasing is unchanged as the bias-current increases.However,GS and ES large-signal eye diagrams show obvious variations during the transition.Relaxation oscillations and large-signal eye diagrams for GS,ES,and total light intensities are numerically simulated and analyzed in detail by using a rate-equation model.The findings show that a complementary relationship between the light intensities for GS and ES lasing exists in both the transition regime and the two-state lasing regime,leading to a much smaller overshooting power and a shorter settling time for the total light intensity.Therefore,the eye diagrams of GS or ES lasing are diffuse whereas those of total light intensity are constant as the bias-current increases in the transition regime. |
