多片式气冷钕玻璃放大器热效应控制技术研究
文献类型：学位论文
| 作者 | 张玉奇 |
| 学位类别 | 硕士 |
| 答辩日期 | 2015 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 王江峰 |
| 关键词 | 激光技术 多片式气冷激光器 热效应 波前畸变 退偏损耗 |
| 其他题名 | Control Technology Research of Thermal Effect in a Multislab Helium Cooled Nd:glass Amplifier |
| 中文摘要 | 随着高功率激光驱动器技术的发展，激光惯性约束核聚变的科学可行性离我们越来越近，下一代高效、高重频激光驱动器也随之提上日程。在高重频固体激光器中，由于重复频率的提高以及散热能力的局限性，激光介质内部产生大量热沉积。不管采用何种热管理技术方案用于耗散增益介质内部产生的热沉积，热传输过程将在介质内部产生热梯度以及不均匀的温度分布，进一步导致应力分布变化与表面形变。温度、应力及表面形变三者对应的光学特性变化就是热效应，它将引起通过的激光束的波面、偏振和光束光强分布的劣化（热致波前畸变和热致退偏）。热效应从寄生振荡、激光输出等多方面增加了激光系统技术难度，它限制了激光器重复频率的提高、光束口径的增大和增益介质的应用范围。 本文将基于多片式气冷放大器实验研究平台，开展热效应的分析与控制，支撑大口径重频放大模块的设计，所做工作主要包括以下几个方面： 1.参与设计了多片式气冷钕玻璃放大器，并针对钕玻璃热学机械参数对热效应的影响进行了研究分析。建立了多片式气冷放大器的热理论分析模型，根据ANSYS和Matalab软件分析模型，构建了放大器的波前畸变分布，然后在此模型基础上分析了钕玻璃各项参数在热沉积条件下对波前畸变的影响，主要参数有：换热系数、热膨胀系数、热导率、弹性模量、泊松比等。在多片式气冷钕玻璃放大器等效热测试系统条件下，对波前畸变结果进行测试，根据测试结果对理论分析模型进行了校正，包括波前畸变的趋势分布以及波前畸变值。该模型较有效的支撑放大模块的结构设计和IFE激光驱动器技术研究工作。 2. 提出通过边缘温度场控制技术对多片式气冷放大器过大的热致波前畸变进行控制的方法，并建立了相应的理论分析模型。基于理论分析和实验测试结果，多片式气冷放大器的大部分热致波前畸变集中在泵浦区边缘，是由于边缘区的侧面散热引起的横向温度场分布引起的。边缘温度场控制技术的核心是控制器边缘温度场分布，进而控制器引起的热致波前畸变。边缘温度场控制技术包括三种技术方案：1）边缘加热技术：通过对增益介质片边缘进行加热，实现边缘区的温度控制；理论分析结果显示在大口径条件下，系统单片波前畸变由2.85λ降低为0.18λ。2）解除Z向自由度，波前畸变主要分布在钕玻璃片的边角处，通过解除Z向自由度，能够有效减少钕玻璃片形变导致的波前畸变；3）全口径泵浦，信号光口径不变的条件下增大泵浦光光束口径与增益介质尺寸相同，减小侧面散热长度与过程降低信号光通光口径内的温度梯度分布，从而减小波前畸变，理论分析结果显示在大口径条件下，系统单片波前畸变由2.85λ降低为0.086λ。 3. 建立了实验验证模块，结合理论分析与实验测试，对边缘加热方案的可行性进行了验证。实验验证模块，通过热流道加热器对钕玻璃边缘进行加热，热流道加热器配有加热线和温控线，可实现温度以及加热功率的远程控制。根据加热方案设计了新型翼片结构，包括翼片加热器的结构设计以及隔热层的设计。新型翼片安置在小型化多片式气冷钕玻璃放大器测试样机中，对在有无边缘加热条件下的波前畸变进行了测试。结果证明波前畸变有了较大的改善，在非加热和加热两种状态，理论分析结果：波前畸变值由1.71λ降低为1.01λ。；实验测试结果，波前畸变由初始状态的1.809λ降低为0.992λ。实验测试结果与理论分析结果相比，在分布特性上存在差异，主要是由热沉铜块与钕玻璃之间的热传导不均匀所致。 4. 为了提高钕玻璃固体放大器的输出性能，开展了钕玻璃再生放大器光谱展宽的技术研究。首先，针对偏振光学元件的偏振性能搭建了测试平台，从而保证实验的可靠性以及安全性。其次，提出了在再生放大器腔内插入双折射石英晶体片抑制增益窄化效应的方法，在该方法的基础上对钕玻璃再生放大器的光谱展宽进行理论分析，并设计相关实验分析验证，理论分析和实验结果均证明，该方法抑制了增益窄化效应和幅频调制效应，在一定程度上提高了系统的光束质量以及安全运行通量。 |
| 英文摘要 | As the development of high power laser driver technology, the feasibility of laser inertial confinement fusion in science is getting closer and closer to us. The next generation of high efficiency, high frequency laser driver has been on the agenda. Because of the limit of thermal dissipation in high frequency solid state lasers, a large number of thermal deposition inside the laser medium is produced. Thermal gradient is formed in the laser medium due to the inhomogeneity of pump light and the inconsistency of cooling ability, which lead to the inhomogeneity distribution of temperature distribution, stress distribution and displacement distribution inside the medium. The uneven distribution of the three factors on the smooth surface which the signal light flux will cause the lower of beam quality (wavefront distortion and depolarization loss) on the one hand, and limit the output energy of the system at the same time. On the other hand, they also can limit the increase of laser repetition rate. Based on the multislab helium-cooled amplifier experiment platform, and in the purpose of improving the beam quality of the system, the article carried out research on the analysis and control of thermal effect, work mainly includes the following aspects: 1. Design the multislab helium-cooled neodymium glass amplifier, and analyze the thermal parameters of the neodymium glass. On the basis of ANSYS and Matalab software to calculate the amplifier wavefront distortion. Then the influences of the neodymium glass parameters under the condition of thermal deposition to wavefront aberration are analyzed on the basis of this model, main parameters include: heat transfer coefficient, thermal expansion coefficient, thermal conductivity, elastic modulus, Poisson ratio, etc. Finally, experimental optical path of Nd:glass amplifier is designed to test wavefront aberration, and correct theory analysis model with the help of test results, including the trend of the wavefront aberration distribution and wavefront distortion value. 2. The wavefront aberration compensation schemes are put forward, and one of which is carried on the thorough analysis. The compensation methods mainly has two kinds: 1) Edge heating methods, just improve the edge temperature of the Nd:glass through hot runner heaters, whose principle is similar to the electric heating wire, but the attach function of hotline and temperature control can realize remote control of temperature and heating power. The wavefront aberration becomes 0.18λ from 2.85λ in condition of large aperture; 2) Make the node dimension free in Z direction, which can effectively reduce the neodymium glass wavefront aberration caused by deformation;3) Pumping the gain medium in a larger size The wavefront aberration becomes 0.086λ from 2.85λ in condition of large aperture. 3. Design the new wing structure in view of the fourth kind of method, including the structure design of the wing heater and the thermal insulation layer. Theoretical analysis indicate that the value of wavefront aberration becomes 1.01λ from 1.71λwith edge heating. At the same time, wavefront distortion in different condition of edge heat are tested under the condition of the new wing, the wavefront aberration becomes 0.992λfrom 1.809λ,and the value decreases by 45.2% ,which won a good compensation effect. 4. The method of beam quality control in neodymium glass regenerative amplifier is proposed, and analyze the results with the designed experiment. First, test platform of the polarized optical components is built in order to ensure the reliability and security of the experiment. And then put forward the method of inserting birefringence quartz crystal in the regenerative amplifier cavity to suppression the gain narrowing effect. Theory analysis of the spectral broadening was developed on the basis of this method. At the same time, related experiment is designed to verify the effect of the method. Theoretical analysis and experimental results have proved that effect of this method to suppress the gain narrowing effect and amplitude frequency modulation effect is obvious. It also can improve the beam quality of the system and the safe operation of the flux to a certain extent. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/16889]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 张玉奇. 多片式气冷钕玻璃放大器热效应控制技术研究[D]. 中国科学院上海光学精密机械研究所. 2015. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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