| Diode-pumped solid-state laser has many advantages,such as light weight,small size,long service life and good stability,etc.Its application fields cover various fields such as industry,military affairs and medicine.The technology of diode array pumped solid-state laser is becoming more and more mature,and its core part is laser gain medium,which plays a decisive role in the characteristics of output laser.Thermal effect is the biggest obstacle to the output performance of laser.One of the basic work of eliminating the thermal effect of laser system is to study the temperature gradient distribution generated by laser devices in the working process,which is also a key work.Only the analysis and simulation of the temperature field can provide the theoretical basis for the further studying thermal effect of laser.With the progress of Nd:YAG ceramic materials preparation technology,the cost performance of Nd:YAG ceramic materials is better than that of Nd:YAG crystal materials.The Nd3+ions in the gain medium of Nd:YAG ceramic laser have typical three-level or four-level structure characteristics,and has high absorption of pump light energy,and has excellent physical and chemical properties.However,under the action of laser and cooling system on ceramics,it is inevitable to produce heat sink,which seriously affects the quality and service life of laser.Therefore,it is still necessary to study the thermal effect of laser.The main contents of this paper are as follows:1.The working principle and structure,pumping mode and operation mode,thermal effect and heat conduction theory of diode-pumped solid-state ceramic laser are described.Due to the working principle of Nd3+doped the laser gain medium is a typical four-level structure,it shows good optical characteristics in application,while the side pumped mode is advantages to output high power beams.Therefore,after combing the theoretical knowledge,this paper chooses the thermal effect of Nd:YAG ceramic laser side pumped by laser diode array.2.In the operation mode of LD array side-pumped Nd:YAG ceramics,the physical models of the light field distribution of one-directional,three-directional,five-directional and multi-directional side-pumped round rod Nd:YAG ceramics were established,and the light field distribution was simulated and analyzed by Mathematica software.Based on the theory of heat conduction,the physical model of LD array side-pumped circular rod Nd:YAG ceramic laser is established,and the analytical solution of the heat conduction equation under pulse pumping condition is solved,and the analytical expression of the transient temperature field is obtained.Calculate the temperature field of a round bar ceramic heat conduction coefficient expression,use Mathematica software for round bar Nd:YAG ceramics time-varying temperature condition is simulated,and analyses the pump power,absorption coefficient,light waist radius,the influence of the cooling water temperature and other parameters on the temperature conditions,simulation analysis of the heat transfer coefficient and heat transfer coefficient of temperature change,The results show that with the decrease of pump power,the increase of waist radius and the increase of absorption coefficient,the central temperature rise of the Nd:YAG ceramic section decreases to some extent.3.The physical thermal model of cuboid Nd:YAG ceramics was established.Combined with the boundary conditions,the steady and transient temperature fields of continuous signal pumping and pulse signal pumping were solved respectively.The temperature fields of variable thermal conductivity coefficients of LD pulse side pump cuboid Nd:YAG ceramics were calculated,and the temperature fields and thermal deformation fields were numerically simulated in Mathematica software.The effects of different pump light waist spot radius,pump power and pulse width on the temperature field of cuboid Nd:YAG ceramics were analyzed quantitatively.The thermal deformation of cuboid Nd:YAG ceramics under thermal steady state was calculated and simulated.The temperature field calculated by analytical analysis method is consistent with the temperature field data calculated by numerical method and finite element method.The research results provide theoretical reference for the reasonable selection of relevant parameters in the design of all solid-state laser,provide theoretical basis for the optimal design of DPSSL and the thermal load bearing capacity,and play a guiding role in the experiment. |
PDF Full Text Request