Design And Experimental Investigations Of Passively Q-switched Two-cavity Dual-frequency Nd:YAG Laser

Dual-frequency pulse laser has a number of advantages such as high peak power,good coherence and large frequency difference,as can be widely used it laser interferometry and coherent detection lidar.At present,in the field of laser radar,the speed of long distance moving target is measured by continuous wave dual-frequency laser and the detection distance is limited by the power of the continuous wave laser.If the high peak power dual-frequency pulse lasers is used as the light source,the farther speed information can be obtained.Therefore,the dual-frequency pulse laser technology has very important research significance.This thesis focuses on the study of dual-frequency pulse solid-state Nd:YAG lasers.The main contents of this thesis are included as follows:First.the principle of single longitudinal mode selection and the commonly used longitudinal mode selection methods have been introduced,the basic compositions of two-cavity dual-frequency Nd:YAG laser have been introduced and the operation principle and operation characteristics have been analyzed theoretically.Second,the theoretical principle of Q-switching technique has been discussed,the operation principle of commonly used Q-switching methods have been introduced,a diode-pumped passively Q-switched two-cavity dual-frequency Nd:YAG laser system has been designed,which uses a structure of T-shaped two standing-wave cavities sharing a common gain medium.A polarizing beam-splitter and a half wave-plate have combined to farm a birefingent flted acting as the laser longitudinal mode selector,and a piece of Cr4+:YAG crystal has been used as a passive Q-switch,thus the p-component and s-component of 1064nm laser light have been forced to oscillate simultaneously in single longitudinal mode in the linear and right angle cavities,respectively,obtaining the output of orthogonally and linearly polarized dual-frequency pulse laser at 1064nm.Third.the characteristics of Cr4+;YAG crystal and its passive Q-switching performance are mostly analyzed.The Cr4+:YAG passively Q-switched laser system has been modeled on the basis of the passively Q-switched rate equations,and the main characteristics of the laser pulse have been analyzed.The rate equations of passively Q-switched two-cavity Nd:YAG laser has been established,and the characteristics of two-cavity pulse laser outputs have been analyzed theoretically.Fourth,an experimental system of the passively Q-switched single-frequency Nd:YAG laser has been set up,and an output of the pulsed single-frequency laser at 1064nm has been obtained.The oscillating mode spectrum of the pulsed single-frequency laser has been measured experimentally,and the pulsed laser has a pulse width of 17ns,a repetition rate of 1.23kHz,and a peak power of 3.06kW when the pump power being 1.06W,the experimental results of which agree well with that obtained by the simulation.The experimental system of the passively Q-switched two-cavity dual-frequency Nd:YAG laser has been set up,both the oscillation and output characteristics of the two-cavity dual-frequency pulse laser have been investigated experimentally,and the experimental results indicate that the frequency-difference of the dual-frequency pulse laser at 1064nm is approximately 10GHz,the repetition frequency,pulse width and peak power of p-polarization single-frequency pulse laser outputting from the linear cavity are 5.8kHz,42ns and 126.4W,respectively,and the repetition frequency,pulse width and peak power of s-polarization single-frequency pulse laser outputting from the right angle cavity are 5.8kHz,40ns and 133.6W,respectively.