In order to attain the optical pulses with high frequency, the pulse-width must be very short. In practical systems, passive Q-switching is mainly regarded as one of the main methods to generate the short optical pulses. In passive Q-switching method, the optical pulses are generated by using laser parameters and therefore, the external electrical or optical modulators are not required to generate the optical pulses. This issue is regarded as the advantage of the passive Q-switching method compared to the other methods. In this paper, a model for two-section passive Q-switching diode laser is proposed. In the suggested method, the changing rates of the carriers are obtained in two regions by solving the equations. As well, by applying this mechanism, the pulse generation is described. Furthermore, the pulse width is achieved and it is demonstrated that the pulse width depends on the physical parameters of the laser.
