大能量纳秒太赫兹参量源研究

发布时间：2018-03-26 04:49

本文选题：MgO　切入点：LiNbO_3　出处：《山东大学》2015年硕士论文

【摘要】：太赫兹波(Terahertz wave)是指频率在0.1 THz-10 THz(1 THz=1012 Hz,波长在30μmn-3mm)之间的电磁波,在电磁波谱上介于微波和红外线之间。太赫兹技术在材料科学、生物医学、信息通信、航空航天、国家安全等领域具有重大的科学价值和广阔的应用前景,是近年来的研究热点。太赫兹波的产生方法主要有两类,分为电子学方法和光学方法。其中光学方法中的光学参量方法是产生太赫兹波的重要方法之一,太赫兹参量源是基于非线性晶体中的受激电磁偶子散射,具有线宽窄,相干性好,室温运转,可调谐等优点；然而,产生的太赫兹波的能量较低。本文分析了太赫兹参量振荡器(TPO)产生太赫兹脉冲能量较低的原因,设计了新的方案,将太赫兹参量振荡器和种子注入式太赫兹参量产生器(is-TPG)结合,产生了大能量太赫兹波,同时研究了太赫兹参量振荡器中的斯托克斯光的调谐输出特性。本论文的主要研究内容包括：1.实验研究了基于MgO:LiNbO3晶体的太赫兹参量振荡器,总结了限制太赫兹参量振荡器产生高脉冲能量太赫兹波的因素：第一,入射泵浦光强度受到MgO:LiNbO3晶体相对较低的损伤阈值的限制,泵浦光的强度不能太大。第二,当斯托克斯光脉冲建立时,泵浦光脉冲被严重消耗。这意味着,在泵浦光脉冲峰值和斯托克斯光脉冲峰值之间有一时间间隔；而太赫兹波的产生与泵浦光强度和斯托克斯光强度的乘积有关,泵浦光脉冲和斯托克斯光脉冲的这种不完全重合减弱了参量过程。第三,由于斯托克斯光谐振腔的限制,还有泵浦光束和斯托克斯光束的小的相位匹配角,泵浦光束的尺寸不能太大。另外,谐振腔内斯托克斯光束尺寸小于泵浦光的尺寸；这样,相对尺寸较小的泵浦光束,还有泵浦光束和斯托克斯光束的空间不完全重合限制了三波的有效重合体积。2.基于以上分析,我们提出了一种新方案,通过利用太赫兹参量振荡器和表面垂直出射的种子注入式太赫兹参量产生器的结合,并且增大泵浦光脉冲能量和光束尺寸,来获得纳秒级高能量太赫兹脉冲。太赫兹参量振荡器的作用是产生斯托克斯光脉冲,被用作为表面垂直出射的种子注入式太赫兹参量产生器的种子。调整泵浦光脉冲和斯托克斯光脉冲的时间间隔来获得完整的空间重合,泵浦光脉冲具有大的脉冲能量和光束尺寸。放大斯托克斯光光束尺寸以使其大于泵浦光光束的尺寸,来获得大的有效重合体积。将太赫兹参量振荡器和斯托克斯脉冲注入太赫兹参量产生器结合来解决这些限制因素,实验数据表明,太赫兹能量输出有了很大的提升。3.研究了在MgO:LiNbO3晶体中基于受激电磁偶子散射的斯托克斯光可调谐波长输出特性,通过改变泵浦光和斯托克斯光的夹角,可获得斯托克斯光的调谐输出,将KTP晶体放入斯托克斯光谐振腔内,获得了绿光的调谐输出。
[Abstract]:Terahertz wave is a kind of electromagnetic wave with a frequency of 0.1 THz-10 THz(1 THz=1012 Hzand a wavelength of 30 渭 mn-3mm. It is between microwave and infrared in electromagnetic spectrum. Terahertz technology is used in materials science, biomedicine, information communication, aeronautics and spaceflight. National security and other fields have great scientific value and broad application prospects, and have become a research hotspot in recent years. There are two main methods for the generation of terahertz waves. The optical parameter method is one of the most important methods to generate terahertz wave. The terahertz parametric source is based on stimulated electromagnetic couple scattering in nonlinear crystal, and has narrow line width. Good coherence, operating at room temperature, tunable, etc., however, the energy of the generated terahertz wave is low. In this paper, the reason for the low energy of terahertz pulse produced by TPO is analyzed, and a new scheme is designed. Combining THz parametric oscillator with seed injection terahertz parametric generator is-TPG, a large energy terahertz wave is generated. At the same time, the tunable output characteristics of Stokes light in THz parametric oscillator are studied. The main contents of this thesis include: 1. The THz parametric oscillator based on MgO:LiNbO3 crystal is experimentally studied. In this paper, the factors that limit the generation of high pulse energy terahertz wave by THz parametric oscillator are summarized. Firstly, the incident pump intensity is limited by the relatively low damage threshold of MgO:LiNbO3 crystal, and the pump intensity cannot be too large. When the Stokes light pulse is established, the pump pulse is consumed seriously, which means that there is a time interval between the pump pulse peak and the Stokes pulse peak. The generation of terahertz wave is related to the product of pump light intensity and Stokes light intensity. The incomplete coincidence of pump light pulse and Stokes light pulse weakens the parametric process. Thirdly, due to the limitation of Stokes resonator, There is also a small phase matching angle between the pump beam and the Stokes beam, so the size of the pump beam should not be too large. In addition, the size of the Stokes beam in the resonator is smaller than the size of the pump beam; thus, the pump beam with smaller relative size, Moreover, the spatial incomplete coincidence of the pumped beam and the Stokes beam limits the effective coincidence volume of the three waves. 2. Based on the above analysis, we propose a new scheme. By combining the terahertz parametric oscillator with the seed injection terahertz parametric generator with vertical surface ejection, and increasing the pump pulse energy and beam size, To get a nanosecond high energy terahertz pulse. The terahertz parametric oscillator produces a Stokes light pulse. Used as seeds for surface vertical ejection seed injection terahertz parametric generator. Adjust the time interval between pump light pulse and Stokes light pulse to obtain complete spatial coincidence, The pump pulse has a large pulse energy and beam size. Amplify the Stokes beam size so that it is larger than the pump beam size, THz parametric oscillator and Stokes pulse injection terahertz parametric generator are combined to solve these limiting factors. Experimental data show that, The energy output of terahertz is greatly improved. 3. The adjustable harmonic output characteristics of Stokes light based on stimulated electromagnetic couple scattering in MgO:LiNbO3 crystal are studied by changing the angle between pump light and Stokes light. The tuning output of Stokes light can be obtained. The KTP crystal is put into the resonator of Stokes light and the tunable output of green light is obtained.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O441.4

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