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.
Highlights
In recent decades, the short pulsed laser has been widely utilized in the fields of production, medical, detection and communication, and so on, as the ultra-short pulse laser technology develops rapidly [1,2]
According to the typical study for the gain switching process of the semiconductor laser, the peak power and width of the output pulses are mainly determined by the accumulation speed after the carrier density reaches the threshold
When the current is injected at time t00, the carrier density increases gradually and achieves the process: When the current is injected at time t ′, the carrier density increases gradually and achieves threshold at time t10 ; the increase rate 0of carrier density is obviously improved and the peak power of output pulse increases as the modulation current becomes larger; the peak power reaches a maximum when the carrier density drops to the threshold at time t20
Summary
The short pulsed laser has been widely utilized in the fields of production, medical, detection and communication, and so on, as the ultra-short pulse laser technology develops rapidly [1,2]. The idea is to excite the first spike of relaxation oscillation, and terminate the electrical pulse before the onset of the second optical spike, resulting in a short light pulse Repeat this process to achieve a pulse sequence on the order of picosecond [10,11]. According to the typical study for the gain switching process of the semiconductor laser, the peak power and width of the output pulses are mainly determined by the accumulation speed after the carrier density reaches the threshold. Based on this theory, a step-pulse modulated signal is proposed on more peak power improvements. The final simulation results show that the proposed method can further compress the laser pulse width and increase the amplitude value
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