The Thermal Analysis Of The Square And The Round Rod Nd:YAG Laser Crystal End Pumped By LD

With the progress of the society,the laser technology is in constant development and progress,The field of application is also expanding.Scientists are also continue working on the latest high-efficiency laser medium,and solid-state laser diode pump has been studied as the mainstream of laser.It not only fully reflects the high efficiency of laser diode pump,but also integrates the advantages of solid-state laser,so it becomes the most efficient laser in the world.The application of high power laser in various industries is more and more.Therefore,it is more meaningful to study the part of energy absorbed by the laser medium into heat when pumping radiation.Heat can increase the temperature of the crystal and even produce thermal stress,which causes deformation,resulting in stress birefringence and thermal lens effect.These effects could damage the optical properties of laser medium,reduces the beam quality,and may even lead to fracture of the laser medium.Especially when the solid laser end pumped by laser diode,it will concentrate on the surface of the laser crystal in a certain range,forming a tiny light spot that causes the thermal power density to become very large in this range.So it is necessary to do the further research about the thermal effect of laser crystal.In this paper,the thermal effects of the square and the round rod Nd:YAG laser crystal end pumped by LD are studied.The all-solid-state laser using laser diode as pump tool is used as the research foundation,and the cooling effect of the system on the crystal is also referenced.The main content as follows:1.This paper introduces the previous research on the laser containing cooling system,and a thermal conduction physics mathematical model with the air heatexchange coefficient is established according to Nd:YAG laser working material.The main method of calculating the temperature of crystal materials when the pump works is the numerical algorithm and the analytical algorithm,and this article introduces the difference between them.2.For the working characteristics of the square Nd:YAG laser crystal that contains the cooling system when the laser works on it,a corresponding thermal conduction mathematical physics model is designed.According to the method of mathematical physics,combined with the cartesian coordinates of the initial conditions and the third kind of boundary conditions that contain the air heat exchange coefficient,the heat transfer model of the square Nd:YAG laser crystal is solved by using knowledge such as the transcendental equation,and the analytical expression of temperature field of the square Nd:YAG laser crystal end pumped by LD is obtained.At the same time,the thermal deformation expression of the working substance is calculated by using the relationship between the thermal deformation of laser crystal and the temperature field.In Mathematica software,the corresponding formula was entered,and the temperature field and thermal deformation distribution of the square Nd:YAG laser crystal were defined and calculated,and the influence of different factors on the temperature field and thermal deformation of the crystal was analyzed.3.For the working characteristics of the round rod Nd: YAG laser crystal that contains the cooling system,a corresponding thermal conduction mathematical physics model is designed based on the crystal of round model.According to the third boundary conditions of the column coordinates and the initial conditions,the analytical expressions of temperature field of the round rod Nd: YAG laser crystal are obtained.According to the hook theorem of temperature?deformation and thermal stress,the general analytic expression of thermal stress is obtained in the round rod laser crystal,which satisfies the three equations of equilibrium?geometry and physics.Mathematica software was used to define temperature field and thermal stress,and simulation was carried out.Based on the analysis of the influence of temperature field,thermal deformation and thermal stress of the Nd: YAG crystal material by the factors such as laser power,spot radius,heat transfer coefficient of air,the analytic expression which has beenobtained can clearly reflect the influence of the various factors on the temperature field,thermal deformation and thermal stress.It can provide theoretical basis for temperature control and system optimization in laser design,which has important reference value.