首页|端面泵浦渐变浓度Nd∶YAG温度场数值仿真研究

端面泵浦渐变浓度Nd∶YAG温度场数值仿真研究

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采用高功率半导体激光端面泵浦技术，在均一浓度Nd∶YAG中心轴沿泵浦光通光方向可产生温度梯度，引起热透镜效应，降低激光输出功率与光束质量。本文结合静态热场数值仿真，建立Nd∶YAG在方形平顶光泵浦条件下的热源方程，研究渐变浓度Nd∶YAG在高功率激光泵浦下的温度分布。当初始泵浦功率为1000 W、泵浦脉宽时间为46μs、重复频率为1 kHz时，均一浓度Nd∶YAG的吸收系数为5。8 cm-1，其中心轴沿通光方向的温度由185 ℃逐次下降到2、4、6、8 mm处的106、51、29、26 ℃;相应地，每经过2 mm，温度下降率分别为39。5、27。5、11。0、1。5 ℃/mm。与此相对应，本文构建出一款渐变浓度Nd∶YAG整体式结构，每段厚度均为1mm，总长度为4 mm。将4段Nd∶YAG的吸收系数依次调控为1。5、2。1、3。3、9。7cm-1，则沿泵浦光通光方向的中心轴温度基本维持在86。5 ℃，在渐变浓度Nd∶YAG中实现沿泵浦光传输方向的温度均匀分布。
Numerical Simulation of Temperature Distribution in End-Pumped Nd∶YAG with Uniform and Gradient Dopants of Nd3+
Objective Nd∶YAG with a uniform dopant of Nd3+can generate gradient temperature distribution along laser propagation under high-power semiconductor diode lasers(LDs),which may cause a thermal lens effect,and thus reduce laser output power and beam quality.Regulating the gradient dopant of Nd3+in Nd∶YAG is paid great attention to for improving the efficiency and beam quality.The traditional regulation method is to fabricate Nd∶YAG with gradient dopant by a unique dual-crucible technology from the Czochralski method.With the development of room temperature bonding technology,it is flexible to obtain designed gradient dopants of Nd3+with specific sample thicknesses in a monolithic structure.We propose a numerical simulation method by establishing heat source equations.The temperature distribution in Nd∶YAG with uniform and gradient dopants of Nd3+under kilowatt pump power is reported accordingly.We hope that the basic strategy can help design a new gradient doped Nd∶YAG monolithic gain media and understand the relationship between temperature distribution and Nd∶YAG with specific dopants along laser propagation.Methods Nd∶YAG is employed for numerical simulation of temperature distribution along laser propagation under high pump power.The aperture of Nd∶YAG is 10 mm× 10 mm cut along the crystallographic axis[100].In the case of bulk Nd∶YAG with a uniform dopant of Nd3+,the absorption coefficient is set as 5.78 cm-1with a bulk length of 8 mm to ensure over 99％absorption of the pump light after single path propagation.In the case of gradient Nd∶YAG,each segment has 1 mm thickness and various absorption coefficients.Meanwhile,a quarter geometric model is built to compare the temperature distribution in the central axis of bulk Nd∶YAG and gradient Nd∶YAG along laser propagation.The initial pump power is 1000 W and the pump pulse width time is 46 μs,with the repetition frequency of 1 kHz.The flat-top pump light is employed for temperature distribution calculation and heat source expression.Results and Discussions Following the pump energy of 46 mJ at 1 kHz,the temperature distribution along laser propagation in the central axis of bulk Nd∶YAG decreases from 185 to 26 ℃.The temperature is reduced to 106,51,and 29 ℃ at the positions of 2,4,and 6 mm in bulk Nd∶YAG,respectively.This indicates that the temperature close to the pump light is the highest in a bulk Nd∶YAG.By adjusting the absorption coefficient to 1.5,2.1,3.3,and 9.7 cm-1for each segment with 1 mm thickness in gradient Nd∶YAG,the constant distribution of temperature around 86.5 ℃ is obtained.The maximum temperature is 88.5 ℃ when the temperature difference between maximum and minimum value is 7.5 ℃.Additionally,by properly designing the sample thickness and absorption coefficient of the gradient Nd∶YAG,the total thickness can be shortened to 4 mm,which is beneficial for ultrashort pulse generation in microcavity.The temperature decrease rate in bulk Nd∶YAG is 34 ℃/mm along the radial direction from the central axis of Nd∶YAG to the thermal sink copper.In the case of gradient Nd∶YAG,the temperature decreasing rate is around 14 ℃/mm.Conclusions A numerical simulation method by establishing heat source equations is proposed for temperature distribution evaluation in bulk Nd∶YAG and gradient Nd∶YAG.The temperature distribution in gradient Nd∶YAG shows a constant distribution of temperature around 86.5 ℃ under pump energy of 46 mJ at a repetition rate of 1 kHz.This confirms that the design of monolithic gain media such as gradient Nd∶YAG can help understand the temperature distribution along the central axis of Nd∶YAG along laser propagation.

uniform Nd∶YAGgradient Nd∶YAGnumerical simulationtemperature distribution

阮芳芳、唐方颖、王锦红、吕彦飞、李家伟、王鑫欣、闫育辉、苏良碧、郑丽和

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杭州医学院医学影像学院,浙江杭州 310053

云南大学物理与天文学院云南省高校光电子器件工程重点实验室,云南昆明 650500

中国科学院上海硅酸盐研究所人工晶体研究中心,上海 201899

均一浓度Nd∶YAG 渐变浓度Nd∶YAG 数值仿真 温度分布

国家重点研发计划国家自然科学基金国家自然科学基金国家自然科学基金云南省科技厅基础研究项目云南省科技厅基础研究项目云南省科技厅基础研究项目云南大学大学生创新创业训练计划云南大学大学生创新创业训练计划云南大学研究生创新项目

2021YFE0104800621650176217520961925508202201AS070013202101AT070162202101BA070001-029202310673085S202310673191KC-23236050

2024

10.3788/AOS231944

光学学报
中国光学学会　中国科学院上海光学精密机械研究所

光学学报

CSTPCD北大核心
影响因子：1.931
ISSN：0253-2239
年,卷(期)：2024.44(7)
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