Gain switching analysis of InAs/InP (113) B quantum dot lasers using external optical beam

For optical data communication, short optical pulses with high peak power are inevitable necessities. Although there are Q-switching, mode locking and gain switching methods to generate short pulses, gain switching method was chosen in this study with the effect of being simpler to obtain short pulses. Since 1.55µm wavelength light gives opportunity to data transmission with low loss, InAs-InP (113) B quantum dot laser which can emit at a wavelength of 1.55µm was chosen to be simulated. Additionally, a comparative analysis was performed for direct and cascade relaxation models. In the simulation, external optical pumping was applied to the excited state and, shorter pulses with a width of 25-40ps and with a high peak power were obtained from the excited state of the laser for single mode and multimode cases. It was also found that the output pulses obtained by gain switching method were not significantly affected by the change in laser parameters in the case of external optical beam application, for both single and multimode simulations, while it was strongly affected by the change in laser parameters in the absence of external optical beam. The results showed that output pulses have long widths and peak power because of the slow decrease in the ground state photon density after the density reaches its maximum value. However, a fast decrease in the excited state photon density after reaching the maximum value yields shorter pulses. When Gaussian optical beam is applied to the excited state of the quantum dot laser, owing to the dominant effect of the excited state transition, the generated pulses become shorter exhibiting a high peak power.