高功率激光装置光学元件“缺陷”分布与光束近场质量统计规律研究

【作者】 周丽丹；

【导师】 张小民； 粟敬钦；

【作者基本信息】 中国工程物理研究院 ， 光学工程， 2009， 硕士

【摘要】 光学元件上微米到毫米量级的灰尘、杂质、划痕、麻点以及亚表面缺陷等“缺陷”是影响高功率激光装置输出性能、制约负载能力提升的“瓶颈”因素。明确“缺陷”分布的表征参量,建立表征参量与装置输出光束近场质量之间的定量关系,并获得光学元件“缺陷”分布指标的分解方法,是目前高功率激光装置负载问题研究中的当务之急。基于上述需求,本论文主要进行了以下几方面的工作:一、定性研究了“缺陷”分布与光束近场质量的空域统计关系:建立了“缺陷”分布空域统计模型,抽象出两个重要的统计参量——“缺陷”总密度和分布幂指数;理论研究了光束近场强度分布的统计性质,得到了统计特征参量——强度平均值和强度对比度;数值分析了线性和非线性传输时“缺陷”分布的空域参量与光束近场质量的关系。结果表明,“缺陷”总密度的增加、分布幂指数的减小都会使近场强度对比度增加,近场质量变坏。二、明确了“缺陷”分布频域统计性质的表征参量——功率谱密度(Power SpectralDensity,简写为PSD);研究了“缺陷”分布PSD的系综平均,并基于“缺陷”分布空域模型研究了“缺陷”分布PSD系综平均与空域统计参量的关系。三、定量研究了“缺陷”分布与光束近场质量的频域统计关系:基于光传输理论,建立了弱调制假设下单一位置及多个位置“缺陷”分布的PSD与近场归一化强度调制PSD的理论关系,验证并讨论了不同传输条件时(线性介质、非线性介质、空间滤波器以及级联介质传输等)二者的具体关系。结果表明,弱调制下,传输后的近场归一化强度调制PSD与引起调制的“缺陷”分布PSD通过系统的传输因子联系,传输因子与系统的构型和运行状态相关。以原型装置助推段为例,基于传输因子研究了不同运行光强下“缺陷”分布对输出近场质量的影响规律。四、探索了基于传输因子的光学元件“缺陷”分布指标分解方法。以原型装置为例,分解了系统关键部位的“缺陷”分布PSD指标。更多还原

【Abstract】 "Defects" on optics such as dust, impurities, scratches, pits and subsurface defects would affect the performance of high power solid-state laser system. It is the main limiting factor in increasing the load capacity of the laser. Finding proper parameters to describe the "defects" distribution, establishing a quantitative relationship between these parameters and near-field beam quality, and setting a method to obtain specifications of optics "defects" distribution are the most urgent things to do to increase the laser power. To achieve these goals, the major research work of this thesis can be listed as follows:1. Relationships between the "defects" distribution and the near-field beam quality were studied qualitatively in spatial domain: spatial statistical model of "defects"distribution was established, two important statistical parameters were abstracted, which were the total density of the "defects" and the power exponent of the "defects" distribution. Statistical property of the near-field intensity was studied theoretically, statistical parameters were obtained, which were the average intensity and the contrast of intensity. Relationships between the "defects" distribution and the near-field quality were researched numerically. The results showed that, the increase of the total density and decrease of the power exponent will increase the contrast of near-field intensity, which would cause the deterioration of the beam quality.2. Power Spectral Density (PSD) was utilized as the parameter to describe the "defects" statistical property in frequency domain. The relationship between the "defects" distribution PSD and one "defect" PSD was researched. Based on the spatial model of "defects" distribution, the relationships between "defects" PSD and spatial parameters were studied.3. Relationships between the "defects" distribution and the near-field beam quality were studied quantitatively in frequency domain: Based on the small modulation approximation, theoretical relation between the "defects" PSD and the near-field intensity PSD was established. Based on the theory of light propagation, the theoretical relation was validated in linear medium, nonlinear medium, and spatial filter. The results showed that, connection between the near-field intensity PSD and the "defects" distribution PSD was the propagation factor of system, this factor is related to system structure and operation parameters.4. Based on the theoretical relation between the "defects" distribution PSD and the near-field intensity PSD, methods to establish specifications of optics "defects" was obtained. Take TIL as an example, specifications of "defects" distribution PSD of key components of this system were deduced.更多还原