The Q-switching technique of LD pumped Nd:YAG laser with high repetition and short pulse-width was studied. According to the theoretical and experimental research, the way to obtain the optimal pulse parameters was presented, which is the theoretical and experimental base for increasing peak power and decreasing pulse width of a Q-Switched laser output pulse. It is of great value for the research of light source of the laser space communication and laser imaging.
Q-switching technique is the key technique of the output pulse of DPL. By using the rate equations, the numerical solution for the trace of a giant pulse and simple expression for the peak power are derived. Therefore the crucial factors of the peak power and the pulse width are the ratio of the initial to the final population inversion ni/nt and the photon decay time tc. As ni/nt increases and the tc decreases, the peak power goes up and the pulse width goes down. From which the optimal parameters of an output pulse can be obtained. According to the analysis above, the way to obtain the optimal pulse parameters was put forward as follows. The power of pumping LD should be as high as possible, while the resonator length as small as possible, and the corresponding optimum reflector should also be selected.
The performance of Q-switch DPL output giant pulse can be optimized by utilized the site of maximum diffraction efficiency of acousto-optic Q-switch. Based on the model of spot acoustic source, spatial distribution of ultrasound field in acousto-optic crystal is studied by numerical calculation with considering the factor of acoustic attenuation. Distribution of diffraction efficiency in acousto-optic crystal is obtained by analysis it. So the site of maximum diffraction efficiency is found, and the same outcome is obtained in experiment. The channel selection technology is put forward based on the study on spatial distribution of diffraction efficiency in acousto-optic crystal that is benefit to obtain optimal parameters (which include the peak power, pulse width, etc) in DPL.