深紫外与真空紫外飞秒激光的产生及应用探索

发布时间：2018-01-18 02:21

本文关键词：深紫外与真空紫外飞秒激光的产生及应用探索　出处：《华东师范大学》2016年博士论文　论文类型：学位论文

【摘要】：紫外超短脉冲激光具有较强的单光子能量,在非线性光学物理中能够产生非线性展宽、频率上转换、高密度等离子、频率合成、化学分解等丰富的物理机制。利用紫外激光的独特优势,脉冲宽度为飞秒量级的紫外光源应用在高次谐波、等离子体透明器件、绿色化学处理、气体痕量检测、激光诱导击穿光谱分析等领域具有广阔的前景。紫外光源还具备多光子电离系数低、成丝等离子体密度高、空间分辨率好等优势,受限于高能量飞秒脉冲的产生及有效控制,此方向上的原理与技术研究仍是国际上研究的热点。本文研究了高能量深紫外与真空紫外飞秒激光的产生与应用,激光输出中心波长分别为266 nm、200 nm和89nm,能量分别达2.2 mJ、0.1 mJ和190 nJ,同时深入探索了不同波长激光脉冲的成丝过程以及其中的物理机制,概括起来可分为以下几个方面：1)运用KBBF直接倍频输出深紫外激光特性,提出倍频-补偿-诊断的全固态深紫外激光系统,基于中心波长为800 nm的钛宝石激光系统经过三倍频后获得266 nm三次谐波,并将输出的400nm激光通过KBBF晶体,利用其直接倍频特点产生高能量的200 nm脉冲输出,并引入棱镜对压缩脉冲,最后运用四波混频原理将266 nm脉冲对200 nm脉冲宽度进行检测。实验首次将0.1 mJ的200 nm深紫外脉冲压缩至飞秒量级,并运用频率分辨光学快门技术对深紫外脉冲进行诊断。2)基于紫外与深紫外激光在惰性气体介质中的非线性混频原理,提出真空紫外波段多色场产生方案,实验中使用重复频率10 Hz的800 nm的钛宝石激光系统,配合级联BBO晶体组产生的266nm脉冲与直接倍频产生的400 nm脉冲在氩气中开展四波混频,在真空中收集到波长分别为200 nm、133 nm、114 nm、100 nm及89 nm真空紫外多色激光,实验首次将紫外光用于进一步产生真空紫外激光的混频过程,并通过调整气压控制入射脉冲的相位匹配,验证了三阶非线性过程中的相位锁定现象。3)基于气体介质中三次谐波的产生原理,提出压力梯度与光丝截断双重增强方案,将上述产生的高能量266nm脉冲分束后聚焦于氩气样品池中分别成丝,将其中一束光焦点处引入真空环境形成气压梯度,在后向收集中心波长为89nm的极紫外激光光谱,并通过另一根深紫外光丝的截断产生了超过5000倍的增强。该实验方案实现两点突破：一方面,在266nm激光脉冲的三次谐波产生过程中,压力梯度环境避免了古依相移现象的产生,改善了相位匹配条件；另一方面,266nm光丝在焦点处对另一路形成干扰,以交叉增强等离子体密度的方式及时将89 nm极紫外光向外围转移,避免了光丝能量回流。双重增强方案为今后更短波长的真空紫外光源产生奠定了原理和技术基础。4)基于等离子体光栅中高功率密度与电子密度特定,创新性地提出了双色场紫外等离子体光栅激光消融技术,以两束400nm紫外激光在空气中成丝并交叉相干形成紫外等离子体光栅,另一束中心波长800nm的红外光丝以布拉格角入射形成增强紫外等离子体光栅。成丝与相干作用产生的等离子体热电子在红外脉冲的加速下碰撞更多的原子产生更强的自由电子密度,因此在激光消融的实验探索中,双色场等离子体方案相对等能量的单根光丝方案在样品靶的消融时间上提升了近6倍。该实验结果具有四点突破：(1)相对长脉冲激光消融技术引入了飞秒光丝的消融方案；(2)验证了飞秒紫外激光产生增强等离子体光栅在激光消融技术中的优势；(3)实验观察到高能量的粒子激发荧光信号；(4)发现激光消融过程中气体介质对结果具有显著影响。最后,深紫外与真空紫外飞秒激光的产生还将在液体动力学分析,化学反应,更深紫外强脉冲形成方面开展更多的实践,有望在光学精密微加工、阿秒脉冲产生、高能态分子激发、超快精密光谱检测等领域产生更多的应用。
[Abstract]:UV ultrashort pulse laser with single photon energy is strong, can produce nonlinear broadening in nonlinear optical physics, frequency conversion, high density plasma, frequency synthesis, chemical decomposition and other rich physical mechanism. The use of the unique advantages of the UV laser, the pulse width of the femtosecond ultraviolet light source used in the harmonic, transparent plasma green chemical processing device, trace gas detection, laser induced breakdown spectroscopy analysis field has broad prospects. The UV light also has a low coefficient of multiphoton ionization, filamentation plasma density, spatial resolution and other advantages, is limited to generate high energy femtosecond pulse and effective control, the direction of the principle and technology research is the international research focus. This paper studies the production and application of high energy deep ultraviolet and vacuum ultraviolet femtosecond laser, the laser output wavelength division For 266 nm, 200 nm and 89nm respectively, energy up to 2.2 mJ, 0.1 mJ and 190 nJ, and further explore the spinning process of different wavelengths of laser pulse and the physical mechanism, it can be divided into the following aspects: 1) by direct frequency doubling of KBBF deep ultraviolet laser output characteristics of all solid state deep ultraviolet laser frequency compensation system is proposed based on the diagnosis, the center wavelength of the Ti: sapphire laser system is 800 nm after three times after obtaining 266 nm three harmonics, and the output of the 400nm laser using KBBF crystal, 200 nm pulse output energy using the direct frequency doubling characteristics, and the introduction of prism compression the pulse, finally using four wave mixing principle of 266 nm pulse of 200 nm pulse width detection. The experiment for the first time 0.1 mJ 200 nm deep ultraviolet femtosecond pulse compression to, and use of deep ultraviolet pulse frequency resolved optical gating technique The diagnosis of.2) nonlinear mixing principle of ultraviolet and deep ultraviolet laser in an inert gas medium based on the vacuum ultraviolet polychromatic field generation scheme, titanium sapphire laser system with 10 Hz repetition frequency in the experiment of 800 nm, with a cascade of BBO crystal group 266nm pulse generation and direct frequency doubling of nm pulse 400 to carry out the four wave mixing in argon, at a wavelength of 200 nm, 133 nm, 114 nm in vacuum collection, 100 nm and 89 nm vacuum ultraviolet multicolor laser, UV light for mixing experiments for the first time will further produce a vacuum ultraviolet laser, and by adjusting the air pressure to control the phase of the incident pulse, and verified in the process of three order nonlinear phase locking phenomenon.3) three harmonic generation principle in gas medium is proposed based on pressure gradient and light silk double truncated enhancement scheme, high energy pulse generated by the 266nm red beam after poly Coke in argon sample pool were silk, a beam of light at the focal point which will be introduced into the vacuum pressure gradient is formed in the environment, to collect center wavelength of 89nm ultraviolet laser spectroscopy, and has produced more than 5000 fold enhancement by truncating the other one deep UV silk. The experimental scheme has two breakthroughs: in three, harmonic 266nm laser pulse generation process, the pressure gradient environment to avoid the Gouy phase shift phenomenon, improve the phase matching condition; on the other hand, the 266nm light wire to form interference on another road to cross at the focus, enhance the plasma density in a timely manner will be 89 nm extreme ultraviolet light to the periphery to avoid the light energy transfer, wire return. Double enhancement program has laid a foundation for the principle and technology of.4 vacuum ultraviolet light source in shorter wavelength) produce plasma grating with high power density and electron density characteristics based on And put forward the innovation of two-color UV plasma grating laser ablation technique, with two 400nm UV laser in air spinning and cross coherent UV plasma grating, infrared light wire the other beam with center wavelength of 800nm to enhance the formation of Prague incident UV plasma grating. The free electron density of the plasma thermal electrons and coherent effects of filamentation in accelerating the infrared pulse collision more atoms produced stronger, therefore in the exploration of laser ablation experiments, two color scheme is relatively single energy plasma filament scheme is increased by nearly 6 times in the sample target ablation time. The experimental results have four breakthroughs: (1 for relatively long pulse laser ablation) ablation technology is introduced into the filament; (2) to verify the femtosecond ultraviolet laser produced plasma enhanced grating in laser ablation technology in the Advantage; (3) observed high energy particle fluorescence signal; (4) it is found that the laser ablation process of gas medium has a significant impact on the results. Finally, the deep ultraviolet and vacuum ultraviolet femtosecond laser generation is also analyzed, the chemical reaction in the liquid dynamics, more intense ultraviolet pulse forming more practice carry out, is expected in the optical precision micro machining, attosecond pulse generation, high-energy excited state molecules, resulting in more applications of ultrafast precision spectroscopy detection.

【学位授予单位】：华东师范大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：O437

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