强激光诱导KDP类晶体光致发光谱特性研究及瓦级大功率单色仪研制
文献类型：学位论文
| 作者 | 罗阳 |
| 文献子类 | 硕士 |
| 导师 | 胡国行 |
| 关键词 | KDP类晶体 KDP/DKDP crystal 光致发光 photoluminescence 激光损伤 laser-induced damage 激光预处理 laser conditioning 能级结构 energy level 大功率单色仪 high-power monochromator |
| 其他题名 | Study on high-power laser-induced photoluminescence properties of KDP crystals and watt-class high-power monochromator |
| 英文摘要 | KDP类晶体是高功率激光系统中重要的非线性光学与光电晶体材料，但激光能量密度的提升受到KDP类晶体激光损伤阈值的制约，进一步提升该晶体的抗激光损伤能力是当前高功率激光系统研究的重心之一。缺陷是诱导损伤的主要因素，国内外对于静态缺陷形态、成分开展了深入研究，但是对于强激光诱导的瞬态缺陷认识较少。谱分析技术，特别是在线谱分析技术对于认识晶体组成成分及其强激光辐照下的变化过程至关重要，是一种分辨瞬态缺陷的有效手段，结合强激光辐照可研究分析强激光与物质相互作用时形成的瞬态缺陷。本文的主要工作包含三部分。其一，构建了强激光辐照下光致发光谱测试结构，探索KDP晶体受强激光辐照时发生的物质结构变化过程；采用谱分析技术研究纳秒、亚纳秒激光预辐照对于DKDP晶体光致发光谱强度的抑制作用，揭示预处理机理；此外，结合光谱学知识，从提升光源功率、收光效率、通光效率以及控制热量出发研制了一套瓦级大功率单色仪。本文具体开展了下列工作： 设计并构建强激光诱导光致发光谱在线探测装置，实验研究了KDP晶体分别受到二倍频与三倍频强激光辐照时的光致发光特性。测试分析晶体在纳秒强激光辐照下未产生损伤时的光致发光谱，确定受激拉曼散射作用在其中发挥关键作用。比较晶体损伤发生前后的光致发光谱特性，分析引起受激拉曼散射的简谐振动在损伤产生过程中的作用，且局部振动增强可诱导电子缺陷（如[HPO4]－）的形成，从而激发了新的光致发光峰。 研究预辐照激光脉宽对激光预处理效果的影响机制。纳秒激光预处理与亚纳秒激光预处理都可以明显地提升DKDP晶体的抗紫外激光损伤能力，其中以亚纳秒激光预处理的提升效果更大。使用商业荧光探测装置分别测量了纳秒与亚纳秒激光预处理后的光致发光谱，结果表明，纳秒与亚纳秒激光预处理均可减弱发光峰的强度，且亚纳秒激光预处理后的降幅更加明显，这表明激光预处理通过消除电子缺陷减少了晶体的非线性吸收，且亚纳秒激光对电子缺陷消除效果更大。 研制了一套瓦级大功率单色仪。设备采用1200W氙灯作为光源，利用椭球反射镜汇聚光束提升了收光效率，选择Czerny-Turner结构作为单色仪的基本结构以提高通光效率、降低能量损失，提升单色光输出功率，实现瓦级单色光输出。研制了一套水冷、风冷系统结合快速热传导的温度控制结构确保瓦级单色仪可长时间、稳定运行于最佳状态，输出波长控制系统则使得输出波长精准可调。单色仪性能经第三方机构检测，且测试结果表明该瓦级大功率单色仪具有输出功率高、温度控制优良、稳定运行时间长的特点，适合开展相关生物效应研究。; KDP/DKDP crystals are essential nonlinear optical and photoelectric materials used in high-power laser systems. However, the increase of laser fluence is limited by the laser damage resistance of KDP/DKDP crystals. Thus, further enhancing the laser damage threshold of these crystals becomes more and more important in high-power laser system. Defects are the precursors which induce laser damage under high power nanosecond laser irradiation. Up to now, in-depth studies have been conducted on the morphology and composition of static defects. However, there are few studies on the laser-induced transient defects. Spectral analysis technique, especially on-line method, is of great significance for understanding the crystal composition and its transient variation under nanosecond laser irradiation, which make it an effective technique to distinguish transient defects. This article focused on the on-line spectral analysis of KDP crystals. First of all, high-power laser-induced photoluminescence detection system was constructed, and the transient defect formed in KDP crystal material under high-power laser irradiation was explored. In addition, spectral analysis technique was used to analyze the defect depression during nanosecond and sub-nanosecond laser conditioning process in DKDP crystals, revealing the mechanism of laser conditioning. Moreover, a set of watt-class high-power monochromator was self-built based on the increase of the power of light source, the efficiency of light collection, the transmission of light passing, and the control of continuous heating process. The details of our works described in the following: Combining high-power laser irradiation and a measurement method for emission spectra, the photoluminescence properties of KDP crystals under high-power irradiation at 355 nm and 532 nm were studied in detail. By comparing emission peaks detected from undamaged sites, it’s believed that Raman scattering dominated this area. By comparing the photoluminescence properties before and after laser breakdown, it is believed that strong molecular vibrations caused by stimulated Raman scattering effect probably should be responsible for the formation of electronic defects, which in turn changed the bandgap of the material, and emitted the new emission peak. The mechanism of nanosecond and sub-nanosecond laser conditioning was studied by the spectral analysis technique. Nanosecond and sub-nanosecond laser conditioning both can significantly improve the laser damage resistance of DKDP crystals, and the sub-nanosecond laser conditioning has a greater improvement effect. The emission spectra of crystal after nanosecond and sub-nanosecond laser conditioning were measured using a commercial fluorescence detection system. The results showed that the intensity of emission peaks was reduced by nanosecond and sub-nanosecond laser conditioning, and the sub-nanosecond laser conditioning had a more pronounced reduction. The results indicated that sub-nanosecond laser conditioning process had a greater effect on depressing electron defects. A set of watt-class high-power monochromator was self-built. A 1200W xenon lamp was used as the light source. An ellipsoidal reflector was applied to improve the efficiency of light collection. The Czerny-Turner structure was selected as the basic structure of the monochromator to increase the efficiency of light transmission and reduce energy loss. Based on the above technique, the monochromatic light power was increased to watt-level. This equipment can operate for a long time and in the best state due to the application of temperature control system, which combines of water-cooling and air-cooling technique. The test results showed that the high-power monochromator had accurate output wavelength, excellent temperature control and long stable operation time. |
| 学科主题 | 材料学 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/31089]  |
| 专题 | 中国科学院上海光学精密机械研究所 |
| 作者单位 | 中国科学院上海光学精密机械研究所 |
| 推荐引用方式 GB/T 7714 | 罗阳. 强激光诱导KDP类晶体光致发光谱特性研究及瓦级大功率单色仪研制[D]. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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