Study On Output Characteristics Of Orthogona L Polarization Conversion Gain-switched Nd:YVO₄ Passively Q-switched Laser

The laser diode pumped Cr⁴⁺:YAG passively Q-switched laser not only has the characteristics of high efficiency,long service life,compact structure,small volume and so on,but also can realize pulse laser output with narrow pulse width and high peak power.It is widely used in the fields of long distance measurement,high-speed holography,laser guidance and laser communication.But Cr⁴⁺:YAG passively Q-switched laser has low controllability,when compared with active Q-switched laser and which results in low stability of the laser output pulse.Especially in the case of high repetition rate,that is far worse than the active Q-switched laser.greatly limits the scope of its application.This will greatly limit Cr⁴⁺:YAG passively Q-switched laser's scope of application.This paper aims to further study this problem.A new method is proposed to improve the output stability of the passively Q-switched laser by realizing the gain mutation in the resonator.A Orthogonal polarization conversion gain switch type Nd:YVO₄ passively Q-switched laser has been designed,and the related theoretical simulation analysis and experimental research are carried out.Its main contents can be summarized as follows:1.This paper studies the factors that affect the stability of passively Q-switched outputs.An orthogonal polarization conversion gain switch is proposed to realize the gain mutation in the cavity,the opening time and the switching speed of the Q-switched are accurately controlled,and then achieves the improvement of the output stability of the passively Q-switched laser.The rate equation of Nd:YVO4 passively Q-switched with orthogonal polarization conversion gain switch type is established.The output characteristics of Nd:YVO4 passively Q-switched laser with orthogonal polarization conversion gain switch type with LD continuous pumping are simulated by using Matlab program.The effects of pump rate on the repetition rate and pulse width of the output laser pulse are simulated.2.Based on the principle of orthogonal polarization conversion gain switch type Nd:YVO₄ passively Q-switched laser,the experimental scheme is designed,and select laser crystal,pump source LD coupling system,electro-optic crystal and saturable absorber reasonably.Application of the basic theory resonant cavity and the theory of the Gauss beam ABCD transmission matrix,we simulate the stable region of the resonant cavity of the passively Q-switched laser with an orthogonal polarization switching gain switch type,and select the appropriate parameters of the laser resonator.3.An experimental device of orthogonal polarization conversion gain switch type Nd:YVO₄ passively Q-switched laser is built to measure the output power,repetition rate and pulse width under different pumped power conditions.The experiment obtained the stable output of passively Q-swiched.Its pulse amplitude fluctuates less than±2.4%,Pulse time volatility less than±5%,and instability of repetition rate less than 1%.The efficiency of optical conversion is 21.27%,and the slope efficiency is 34%.The tunable range of repetition frequency is 7.8-49.16 kHz,and the pulse width is within the range of 26.28-49.79ns.The single pulse energy is up to 95.2?J and the peak power is 3.62kW.At the same time,the output parameters of the conventional passive Q-switched laser are compared to verify that the orthogonal polarization conversion gain switch type laser can improve the stability of the passively Q-switched laser output under the same experimental conditions.