Step-Pulse Modulation of Gain-Switched Semiconductor Pulsed Laser

Abstract

To improve the peak power and extinction ratio and produce ultra-short pulses, a novel approach is presented in this paper offers a highly effective modulated method for a gain-switched semiconductor laser by using step-pulse signal modulation. For the purpose of single pulse output, then the effects on the output from the gain-switched semiconductor laser are studied by simulating single mode rate equation when changing the amplitude and width of the modulated signal. The results show that the proposed method can effectively accelerate the accumulation speed of the population inversion and we can acquire the output pulse with higher peak power and shorter width. Compared with the traditional rectangular wave modulation, this method is advantageous to obtain a high gain switching effect by increasing the second modulation current and reduce the pulse width to saturation at the best working point. It can be incorporated as a practical and cost-effective approach for many fields which need high extinction ratio short pulse, such as the optical time domain reflectometry.

Achieving High Power Continuous Wave and Short Pulses of Semiconductor Laser for Use in Photodynamic Therapy

“…This PP type appears when m ≥ 1 with fm≥ 0.5fr as we will see in figure 10 and is caused by gain switching from under to above threshold during the lower cycles of I(t) to above threshold during the upper cycles [23]. This type corresponds to the spike generation predicted by [43,44] when the pulse is too short. Figure 7 characterizes this PP type when m =1.5 and fm=fr.…”