Temperature Field Analysis Of LD Pumped Nd:YAG Crystal Heat Capacity Laser

Since the year 1990,when C.T.Walters(and his co-partners)from the Lawrence Liver-more Laboratory(the U.S.)began their relative studies,heat capacity laser has gradually been widely used in such aspects as medical,industrial,military and etc.,making it expect-ably applicable in manned spaceflights in the future development.So far it has become one of the world’s most powerful lasers.Diode pump solid state laser(DPSSL),due to its advantages like high stability,long lifespan of usage,small volume and so on,has played a significant role in current society.Different from any other ordinary laser,the operating mode of solid-state heat capacity laser(SSHCL)is between single pulse and steady state,with pumping phase and cooling phase working separately.Able to provide higher-quality output beam,such operating mode proves to be more suitable for high power laser output.Not just fully reflecting the advantages of the laser diode but also combining those of heat capacity laser,DPSSL has become the world’s most powerful laser.However,the quality of output beam can be seriously affected in the working process,when the useless heat causes non-uniform temperature increase of the laser crystal.Therefore,how to effectively control the thermal effect of heat capacity laser has turned to be one of the researching focuses.In this paper,end-pumped LD is chosen as the case of study,with the Nd: YAG crystal in use.The Nd:YAG crystal,due to its good physical and chemical properties,has often been used in different sorts of lasers.In normal studies of thermal effects,the thermal-conductivity coefficient of Nd:YAG laser crystal is usually regarded as a constant.While in this paper,it is supposed to be more practically valuable as the calculation of the temperature field and the study of thermal effect are based on the basic law that thermal-conductivity coefficient of Nd:YAG crystal varies in the way the temperature changes.This paper analyses the facts of heat capacity laser thermal effect and provides a bunch of measures to cure the heat deposition.Firstly,the conventional history of the development of heat capacity laser at home and abroad is reviewed and the advantages of laser diode-pumped solid-state heat capacity laser and research focus are described.Comparisons in operating mode are made between the heat capacity laser and conventional lasers and the root causes of heat generated effect are analyzed.A brief introduction to various parameters of the Nd: YAG crystal is made in addition.Secondly,Three types of laser crystals are studied: rectangular laser crystal,rod-shaped laser crystal and the new microchip temperature field.Simple thermal model of rectangle laser diode-pumped laser crystals,rod-shaped laser crystals and microchips are established.Temperature field analysis of single and double end-pumped with pumping stage and cooling stage of rectangular crystal and rod crystal is made.In the calculation,taking it into consideration that the thermal-conductivity coefficient of Nd:YAG crystal is a varied function with the changes of temperature,the author calculated the temperature field of single and double end-pumped with pumping stage and cooling stage of rectangular crystal,rod crystal and those of microchip,with the usage of reasonable boundary conditions and initial conditions.Finally,Based on the temperature field theoretical formulas,the temperature field of single and double end-pumped with pumping stage and cooling stage of rectangular crystal,rod crystal and microchip crystal is simulated with the help of a software called Mathematic7.0.Comparisons are made between the temperature field with heat transfer coefficient as a fixed value and heat transfer coefficient as a varied function in single end-pumped stage.After temperature field are simulated,the author researched the effect on temperature field with different pumping time and different pumping pot radius.The result of the study is proved to be correct and reliable after being compared with the data in published papers,supposed to play a directional role in solving thermal problems in heat capacity laser systems.