偏振依赖太赫兹二维谱的理论与实验研究

Terahertz two-dimensional spectroscopy (2DTS) is a new technology developed from two-dimensional spectroscopy and terahertz time-domain spectroscopy. The current 2DTS can be seen as independent of polarization, in which physical processes are excited by a pair of parallel polarization terahertz pulses. As a result, the physical processes excited by a pair of cross or non-parallel polarization terahertz pulses cannot be researched by the current 2DTS. A polarization dependent 2DTS measurement system will be built in this project, in which the physical processes are excited by a pair of non-parallel polarization terahertz pulses that are obtained via using femtosecond laser pumping lithium niobate to produce linear polarization terahertz pulses, and via using a wire grid polarizer to adjuste the polarization state of the terahertz pulses. Based on the theory of electrodynamics, quantum mechanics and semiconductor physics, a polarization dependent 2DTS theoretical model will be set up, which will provide the basis for analyzing the polarization related physical process and material properties from the 2DTS. On this basis, it will be researched by the polarization dependent 2DTS that the terahertz wave excited electrons in graphene and the terahertz Hall effect in GaAs. By putting the polarization terahertz pulse generation and control technology into the current 2DTS technology, a polarization dependent 2DTS measurement method and technology will be innovated out in this project. A kind of polarization dependent terahertz two-dimensional spectroscopy physics and technology will be made through the combination of our theotical analysis and experimental meausrement, so as to reveal the new laws of physics and phenomenon, having profound scientific significance.

太赫兹二维谱(2DTS)是在二维谱和太赫兹时域光谱基础上发展起来的崭新技术。目前的2DTS可视为偏振无关的：物理过程由一对平行偏振的太赫兹脉冲所激发，不能研究需要交叉偏振等非平行偏振下才能激发出的物理过程。本项目以飞秒激光激励铌酸锂产生线偏振太赫兹脉冲，以线栅偏振片调节脉冲的偏振状态，来获得一对非平行偏振太赫兹脉冲，构建偏振依赖2DTS测量系统。以电动力学、量子力学和半导体物理等理论为基础，建立偏振依赖2DTS理论模型，为从2DTS中分析偏振相关的物理过程和材料特性提供理论依据。在此基础上，研究与石墨烯太赫兹激发电子和砷化镓太赫兹霍尔效应等物理过程相关的2DTS。本项目通过将偏振太赫兹脉冲的产生与控制技术融入2DTS中，创新出偏振依赖2DTS测量方法与技术。力图通过理论与实验的结合，建立起一种偏振依赖太赫兹二维频谱物理与技术，借以揭示新的物理规律和现象，具有深刻的学术价值和重要的科学意义。

以经典物理中电动力学、物理光学和半导体物理等理论为基础，针对半导体薄片样品和交叉极化入射的太赫兹脉冲，建立了偏振依赖太赫兹二维谱的经典理论模型，描述太赫兹波与材料的相互作用，为从二维太赫兹谱中分析偏振相关的物理过程和材料特性提供了理论基础。基于偏振依赖二维太赫兹谱理论模型，具体研究了基于霍尔效应在GaAs中实现太赫兹二维谱的相关物理过程，给出了基于矩阵理论的近似解析解和基于耦合波方程的严格解析解，揭示了其中的物理规律和现象，为建立起一种偏振依赖太赫兹二维频谱物理与方法提供了理论基础和技术途径。为搭建太赫兹二维谱测试系统，利用3D打印技术制备了一系列基本太赫兹光学元件，研究了一系列太赫兹频谱技术、太赫兹空间光场调控技术、太赫兹无损检测技术和太赫兹功能器件等。在此基础上，用飞秒激光激励非线性晶体产生线偏振太赫兹脉冲，采用线栅偏振片调节太赫兹脉冲的偏振状态，采用电光采样方式测量太赫兹脉冲，构建了偏振依赖共线式太赫兹二维谱测量系统，分辨和读取偏振依赖共线式太赫兹二维谱中的太赫兹信号，为研究偏振依赖太赫兹二维谱提供了基本实验平台。