超强超短激光系统时间对比度提升技术研究
文献类型：学位论文
| 作者 | 许毅 |
| 学位类别 | 博士 |
| 答辩日期 | 2014 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 冷雨欣 |
| 关键词 | 超强超短脉冲激光，啁啾脉冲放大，脉冲净化，时间对比度 |
| 其他题名 | Research on the enhancement of temporal contrast in ultra-intense and ultra-short laser system |
| 中文摘要 | 超强超短脉冲激光技术自二十世纪八十年代以来获得了飞速的发展，目前世界上很多研究机构正在竞相研制10拍瓦量级的超强超短激光系统，在未来激光脉冲的聚焦强度有望突破1023W/cm2。在如此高的聚焦强度下，脉冲前沿强度较大的噪声可能会先于主脉冲与靶面发生作用，产生预等离子体，从而破坏激光与物质相互作用的物理机制。因此，随着激光聚焦强度的不断增加，脉冲时间对比度（可定义为时域上噪声强度与主脉冲强度的比值）问题变得日益重要，已成为发展超强超短激光系统所必须解决的一个瓶颈问题。本文依托中国科学院上海光学精密机械研究所研制的太瓦及拍瓦量级钛宝石激光系统，重点开展了超强超短激光系统时间对比度提升的相关技术研究。 本论文探讨了超强超短脉冲激光系统中噪声的起源，分析了不同脉冲净化方式的技术特点，并在此基础上基于两种新型的脉冲净化技术在太瓦及拍瓦量级的钛宝石激光系统中成功地实现了时间对比度的显著提升。主要的研究成果如下： 1. 基于飞秒光参量放大及倍频新技术，有效提升了太瓦量级钛宝石激光系统的时间对比度，使激光系统的时间对比度（主脉冲前沿100ps外）从原有的2×10-8提升至6×10-12。并研究了不同种子脉冲能量及不同的预放大器对放大后输出脉冲时间对比度的影响。 2. 基于飞秒光参量放大及倍频新技术，实现了峰值功率达0.8PW、皮秒域对比度（主脉冲前100ps外）达10-12量级的飞秒激光脉冲输出。并利用双普克尔盒和可饱和吸收体，有效地抑制了再生放大器中逸出的纳秒域的预脉冲。开展了初步的质子加速实验研究，通过比较不同时间对比度条件下的物理实验结果，验证了拍瓦激光系统时间对比度的提升。 3. 创新发展空心光纤空间整形及交叉偏振波产生技术，研制了一个具有高时空质量的脉冲净化装置。该装置可输出能量为105μJ、对比度达10-12量级的净化脉冲。净化脉冲具有良好的空间光束质量，其光谱宽度为65nm（FWHM），可支持亚15fs的脉冲宽度。该脉冲净化装置可为拍瓦钛宝石激光系统提供优质的种子脉冲。 4. 将上述脉冲净化装置产生的大能量、高对比度种子脉冲注入到拍瓦级钛宝石激光系统，可以使拍瓦激光系统的脉冲对比度（主脉冲前沿100ps外）从原有的~10-8提升至1.7×10-11。且通过控制光谱在放大过程中的演变，可以使压缩后支持27fs的脉冲宽度，对应的脉冲峰值功率可达~1.3PW。 |
| 英文摘要 | Ultra-intense and ultra-short pulse laser technologies have been rapidly developed over the past decades. At present, many research institutions in the world are competing for the development of 10 Petawatt laser system, and the focused intensity of the laser pulses will exceed 1023W/cm2 possibly in the future. Under such a high focused intensity, the intense noise in the laser pulses can generate pre-plasma before the main pulse arrives at the target and destroy the physical dynamics of the laser-matter interaction. Therefore, pulse temporal contrast (defined as the ratio of the noise intensity to the main pulse intensity) is becoming increasingly important with the significant development of pulse focused intensity, and it has already become a bottleneck for the development of ultra-intense and ultra-short laser system. This dissertation is based on the terawatt and petawatt Ti:sapphire laser system built in the Shanghai Institute of Optics and Fine Mechanics, CAS. It is focused on the research on temporal contrast enhancement in the ultra-intense and ultra-short laser system. In this dissertation, the origination of noise in ultra-intense and ultra-short laser system was studied, and the technical feature of different pulse cleaning method is also analyzed. Based on two novel pulse cleaning methods, significant enhancement of pulse temporal contrast was achieved in the terawatt and petawatt Ti:sapphire laser. The main work and the main results are summarized as follows: 1. Based on femtosecond optical parametrical amplification and second harmonics generation, improvement of pulse temporal contrast in a terawatt Ti:sapphire laser was achieved. the pulse temporal contrast (100ps before the main pulse) was enhanced from original 2×10-8 to 6×10-12. Moreover, the evolution of pulse temporal contrast under different seed pulse energy and different pre-amplifiers were also studied. 2. Based on femtosecond optical parametrical amplification and second harmonics generation, high-contrast laser pulse with peak power of 0.8PW was obtained. The temporal contrast in picosecond scale was about 10-12 (100ps before the main pulse). In addition, by utilization of double Pockels cells and saturable absorber, pre-pulses leaking from the regenerative amplifier were also suppressed in nanosecond scale. The high-contrast petawatt Ti:sapphire laser was applied for experiments on acceleration of proton with foil target, different physical phenomenon were observed under different contrast condition. The experimental results also demonstrated the enhancement of temporal contrast in the petawatt Ti:sapphire laser. 3. Combining hollow-core fiber spatial filtering with cross-polarized wave generation, a pulse cleaner with high temporal-spatial quality was developed. High-contrast (10-12) seed pulses with 105μJ energy and uniform beam profile can be generated by the pulse cleaner. The spectral width of the clean pulses was over 65nm (FWHM), which can support sub-15fs pulse duration. This pulse cleaner can sever as an excellent injector for the petawatt Ti:sapphire laser. 4. High-energy and high-contrast seed pulses generated by the pulse cleaner above were injected into the petawatt Ti:sapphire laser, the ultimate pulse temporal contrast (100ps before the main pulse) was enhanced from original ~10-8 to 1.7×10-11 , while the recompressed pulse duration was improved to be 27fs by controlling the spectral evolution in the amplifiers, and the maximum pulse peak power can support ~1.3PW. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15870]  |
| 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 | 许毅. 超强超短激光系统时间对比度提升技术研究[D]. 中国科学院上海光学精密机械研究所. 2014. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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