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题名	高对比度超短激光脉冲源技术研究
作者	王建州
学位类别	硕士
答辩日期	2012
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	超短超强激光，啁啾脉冲放大（CPA），交叉偏振波（XPW），光学参量放大（OPA）
其他题名	Research on high-temporal-contrast ultra-short laser source technology
中文摘要	啁啾脉冲放大（Chirped Pulse Amplification，CPA）技术的发明和广泛应用，使得超短激光脉冲通过放大并聚焦后，峰值功率密度可以达到1021W/cm2乃至更高量级水平。如此高的峰值功率密度，为众多学科领域的前沿研究提供了前所未有的实验手段和极端实验条件。但伴随着峰值功率密度的提高，预脉冲和自发辐射放大（amplified spontaneous emission，ASE）本底的强度也相应提高。预脉冲和自发辐射本底达到一定强度时就会与目标靶产生破坏性的相互作用，改变主脉冲与目标靶相互作用的过程，甚至阻止主脉冲与目标靶作用。另一方面，随着激光与物质相互作用物理等研究的发展，尤其是一些特殊形态的相互作用靶的提出，例如用于质子产生和加速的破坏阈值很低的纳米薄膜靶等，也对超短超强激光脉冲的预脉冲和自发辐射本底抑制提出了新的更高的要求。因此，在提高主脉冲峰值功率的同时，抑制预脉冲和自发辐射本底的强度，提高超短超强激光脉冲的时域对比度（定义为主脉冲强度与预脉冲或ASE本底强度的比值）已经成为当前超短超强激光研究与应用的重点之一。 本论文针对超短超强激光脉冲时域对比度提高的关键科学技术问题展开研究，主要基于交叉偏振波（Cross Polarized Wave，XPW）产生、红外光学参量放大（OPA）和倍频（SHG）等技术，发展高对比度的超短激光脉冲源技术，并应用于已有的钛宝石CPA超短超强放大系统中。通过研究注入种子源对比度与放大后脉冲对比度之间的关系，发现利用大能量高对比度种子源作为前端，可以有效地提升CPA放大后的超强超短激光脉冲的对比度。主要研究内容包括： 1. 对800nm波段的XPW技术进行了深入的研究，发展基于双BaF2晶体XPW产生的高对比度超短激光脉冲源。设计并搭建了一套基于双BaF2晶体的脉冲净化装置，对800nm 波段商品化钛宝石飞秒激光器输出脉冲进行净化，提高脉冲时域对比度。测量得到1011 对比度的大能量超短激光脉冲，比初始脉冲对比度有三个量级的提高，整套装置输出效率22%。 2. 发展了1053nm波段基于OPA级联SHG技术的高对比度超短激光脉冲源。基于商品化的800nm钛宝石飞秒激光器，参与发展并搭建了多级OPA放大器，调谐获得了2106nm波段稳定输出的超短强激光脉冲，进一步采用BBO晶体把2106nm光倍频到1053nm，实现脉冲对比度的提高，验证了1011对比度的超短强激光脉冲。 3. 开展了800nm波段高对比度超短激光脉冲源在超短超强激光系统中的应用研究。将上述800nm波段基于XPW的高对比度脉冲做为种子，引入已有的太瓦级超短超强钛宝石CPA激光放大系统。研究不同能量种子光输入，以及不同对比度种子光输入对最终输出超短超强激光脉冲对比度的影响。实验验证了，以较大能量高对比度超短强激光脉冲作为种子，能有效地提高超短超强CPA激光系统最终输出激光脉冲对比度。
英文摘要	The invention and wide usage of chirped pulse amplification (CPA) technology make the peak intensity of amplified ultra-short pulses reach 1021W/cm2 level. Such a high intensity provides an unprecedented new experiment method and extreme experimental conditions never achieved before for many scientific fields. The intensity of prepulses and amplified spontaneous emission (ASE) background increases as the peak intensity of the main pulse soaring. When the intensity reaches a certain level, the interaction between the prepulses and the target is destructive which will change the process of interaction between the main pulse and the target, even worse, prevent the main pulse from interacting with the target. On the other hand, with the development of laser matter interaction physics, some special targets for interaction have been proposed, for example, the nanofilm target with very low damage threshold which is used for proton generation and acceleration. These all require a higher level of suppression of the prepulse intensity and ASE background intensity for ultra-intense and ultra-short pulses. Thus, with the peak intensity of the main pulse increasing, suppressing the intensity of prepulses and ASE background to enhance the temporal contrast (defined as the ratio of the maximum intensity in the main pulse to the level of ASE background or prepulse) of ultrahort ultraintese laser pulses has become one of the key points in ultrahort ultraintese laser research and application. This dissertation carries out studies aimed at few pulse temporal contrast enhancement technologies, such as cross polarized wave (XPW) generation and optical parametric amplification (OPA) plus second harmonic generation (SHG). High-contrast ultra-short laser sources based on these technologies are used to seed the home built TW level CPA laser system. Through the study of relation between the temporal contrast of input source and the temporal contrast of the amplified pulse, we find that the temporal contrast of the amplified pulses can be enhanced effectively when using laser sources with high energy high temporal contrast as front end. The main research subjects are as following: 1. A high-contrast ultra-short laser source based on double BaF2 crystals XPW generation technology is developed. Double BaF2 crystals XPW generation in 800nm is studied thoroughly. Taking advantage of XPW generation in BaF2 crystal, we designed and constructed a pulse cleaning device based on double BaF2 crystals to clean the output pulses of a commercial Ti: sapphire fs CPA laser. High energy ultra-short pulses with temporal contrast of 1011 are obtained, which have an improvement of three orders of magnitude to the initial pulses. The overall output efficiency of the system is 22%. 2. A high-contrast ultra-short laser source based on OPA plus SHG technology in 1053nm is developed. Multi-stage OPA amplifier based on commercial Ti: sapphire 800nm fs CPA laser is constructed. High energy ultra-short pulses with high stability in 2106nm can be obtained by OPA tuning. Using the SHG effect in BBO crystal, we get high energy ultra-short pulses in 1053nm, whose temporal contrast reaches 1011 level. 3. Researches on application of high-contrast ultra-short laser sources in ultra-short ultra-intense CPA laser system are carried out. The high-contrast pulses are used to seed the home build TW level ultra-short ultra-intense Ti: sapphire CPA laser system. Experiments have been carried out to study how the temporal contrast of the amplified pulses varies with the energy and the contrast of the seeding pulses. The experimental results show that using high-energy high contrast pulses to seed the Ti: sapphire CPA laser system can enhance the temporal contrast of the final amplified pulses effectively.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/16719]
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	王建州. 高对比度超短激光脉冲源技术研究[D]. 中国科学院上海光学精密机械研究所. 2012.

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