Research On Temperature Characteristics And Control Methods Of High-repetition Frequency Microchip Laser

Microchip laser has the characteristics of compact structure,small size,high electrooptical conversion efficiency,long service life,etc.,and has been applied in the fields of lidar,optical storage and optical communication.However,the small size also causes the microchip laser to be affected by the thermal effect.When the laser is running,its average output power and beam quality are reduced to varying degrees,so it is necessary to control temperature of the laser.Based on the heating mechanism of laser diode,the corresponding geometric model and temperature distribution model are established.The temperature distribution of the laser diode is simulated by finite element software.For gain medium,this paper mainly studies the effects of Q-switching repetition frequency and pulse pumping frequency on its temperature,and also analyzes the temperature characteristics of crystals under different cooling conditions,different pump optical power,pump beam waist radius and pump light distribution patterns.After studying the temperature distribution of the laser,a monolithic temperature control scheme is proposed,and a physical model is established,then the mathematical model of the whole temperature control system is derived.According to the characteristics of the control object,the first-order lag approximation is performed on the mathematical model.Aiming at the time lag of the control system,based on the fuzzy PID controller,the variable universe theory is introduced,that is,the error is graded,and different scaling factors are used in different intervals,which is equivalent to the addition of control rules,and then the universe of fuzzy controller is adjusted in real time.The control effects of conventional PID,fuzzy PID and variable universe fuzzy PID are compared in MATLAB/SIMULINK.The results show that the variable universe fuzzy PID control has better stability and anti-interference ability.Finally,the control method is implemented by hardware design.The temperature control system uses the STM32F103RET6 chip as the control core,the DRV592 as driver chip of the thermoelectric cooler(TEC),and the platinum resistance as temperature sensor to measure the temperature of the laser,achieving closed-loop negative feedback control of the laser.Through experimental analysis,the control accuracy and stability of the temperature control system are ideal.