光丝能量交换增强周期量级脉冲驱动的太赫兹辐射的研究

The researchs on terahertz (THz) emission from air plasma produced by few-cycle laser pulses and interaction with crossed filaments become the world's hot spots. The purpose of this project is to study the effect on THz emission (waveform, amplitude) from air plasma produced by few-cycle laser pulses by the crossed filaments and relationship between the characters and the carrier-envelope phase (CEP) of driving laser pulses. Based on the plane wave coupling theory, the characters of few-cycle driving laser pulses after the coupling crossed filaments are calculated and analyzed; Combining with the transient photocurrent model and THz transmission model, the characters of THz emission from air plasma are calculated and analyzed, and the relationship between the characters and the CEP of driving laser pulses will be obtained. In experimental research, parameters of THz emission after the coupling crossed filaments will be measured; Under various CEP of few-cycle pulses, the intensity and waveform of THz emission, whose dependence on the CEP of few-cycle pulses are studied, and then comparison to the condition of single air filament. The significance of this project is that the waveform and intensity of THz generated from air plasma will be controllable by the coupling crossed filaments and adjusting CEP of driving laser pulses, which is helpful for obtaining enhanced THz emission. This reveals the physical nature of air filamentation and the THz generation. Determining of CEP value of driving laser according to the CEP effects during the THz emission, which has very important significance for the application of ultra wide-band laser pulses, especially for the isolated attosecond scientific research.

周期量级脉冲空气成丝产生太赫兹辐射以及光丝交叉相互作用的研究是世界范围内的热点。本项目旨在研究光丝相交对周期量级脉冲在空气中成丝辐射太赫兹波的幅度、波形的影响以及太赫兹波与驱动脉冲的载波-包络相位(CEP)的关系。理论上，利用平面波耦合理论分析两束光空气成丝耦合相交后的周期量级驱动脉冲的参量；结合光电流模型和太赫兹产生传输模型分析成丝辐射太赫兹波的各参量以及与驱动脉冲CEP的关系。实验上，对光丝耦合相交后辐射太赫兹波的各参量进行测量；改变驱动脉冲的CEP，研究太赫兹波幅度、波形与CEP的相关性，并与单丝情况进行对比。本项目的意义：通过光丝耦合和改变驱动脉冲的CEP，实现对空气成丝辐射的太赫兹波幅度、波形的控制,有望得到增强的太赫兹波，揭示成丝和太赫兹波产生的物理本质；基于太赫兹辐射中的CEP效应，反推得到驱动脉冲的CEP，对超宽频带激光脉冲的应用，尤其对阿秒科学有重要的意义。

超短激光脉冲在空气中成丝驱动空气等离子体产生太赫兹辐射，是光学领域前沿的课题，可运用到安全以及基础物理和文化遗产的应用中。两束光丝耦合相交越来越受到学者们的关注，是优化和控制光丝在空气中的传播的有效的全光学的控制方式。但利用光丝耦合相交实现太赫兹辐射的控制仍需进一步的研究。本项目研究了两束光丝耦合相交产生幅度和极性可控的太赫兹辐射，以期更深入的认识空气成丝的物理本质以及空气成丝产生太赫兹辐射的物理过程。获得的研究成果如下：.1.利用两光束光场激发气体形成等离子体光丝耦合相交，控制两光丝耦合相交位置和相对延时，实现了对太赫兹辐射幅度和极性的控制，进一步认识和了解光丝耦合相交以及太赫兹辐射产生的物理过程。.2.通过控制周期量级激光脉冲的载波包络相位(CEP) 和两束光空气成丝耦合相交的条件，获得光丝耦合相交后的太赫兹辐射中的CEP效应，获得了波形可控的太赫兹辐射。.3.利用正交偏振双色场成丝平行耦合相交，通过控制正交偏振双色场的相对相位差和控制产生的等离子体长度来控制太赫兹辐射的偏振态。