基于等离子体诱导透明/铁电超晶格的太赫兹非线性调制特性的研究

The research of terahertz wave modulation technology is one of the key technologies which is urgently needed to be solved in terahertz communication system. Combined with the nonlinear dielectric properties and transient response properties of ferroelectric materials, the ferroelectric superlattices were fabricated on barium strontium titanate / strontium titanate superlattices. High power terahertz wave modulators with plasma-induced transparency structure were fabricated on the surface. The influence of the composition, thickness and number of layers on the dielectric properties of ferroelectric superlattice is studied systematically, and the corresponding high-power terahertz wave modulation device is prepared. Secondly, the influence of the change of plasma-induced transparent local electric field on the dielectric nonlinear modulation of ferroelectric superlattice is studied, and the intrinsic relationship between the transmission amplitude of plasma-induced transparent structure and the nonlinear refractive index distribution of ferroelectric superlattice is established. The nonlinear modulation mechanism of terahertz wave modulator is revealed. Finally, the polarization relaxation process of ferroelectric superlattice is studied, the microcosmic relaxation characteristics of ferroelectric superlattice and the influence rule of polarization mechanism are explored, and the transient response mechanism of high power terahertz wave modulation devices is revealed. The successful implementation of this project will provide a theoretical and experimental basis for the development of a new high-power terahertz wave modulator. It is of great theoretical and practical significance for the future development of the high-speed broadband wireless communication system with terahertz wave.

太赫兹波调制技术是太赫兹波通信的关键技术之一。结合铁电材料所具有的非线性介电性质和瞬态响应特性，本项目对以钛酸锶钡/钛酸锶铁电超晶格为衬底，并在其表面上制备具有等离子体诱导透明结构的非线性太赫兹波调制器件进行研究。首先系统地研究铁电薄膜的组分、厚度以及层数对铁电超晶格介电性质的影响规律，在此基础上制备相应的非线性太赫兹波调制器件；其次研究等离子体诱导透明局域电场的变化与铁电超晶格介电非线性调制之间的相互影响，建立等离子体诱导透明结构透射振幅与铁电超晶格非线性折射率分布之间的内在联系，揭示太赫兹波调制器的非线性调制机理；最后研究铁电超晶格的极化驰豫过程，探索铁电超晶格的微观驰豫特征及极化机制的影响规律，揭示非线性太赫兹波调制器件的瞬态响应机理。本项目的顺利实施将为研制新型非线性太赫兹波调制器提供理论和实验依据，对于未来太赫兹波高速、宽带的无线通信系统的发展具有重要的理论和实际意义。

研制和开发高性能的太赫兹波调制器件，实现对太赫兹波高效的操控是当前太赫兹通信技术发展中迫切需要解决的问题。本项目围绕钙钛矿材料与等离子体诱导透明结构相干耦合效应开展了以下研究工作：1）研究了铁电超晶格的层数、退火温度对铁电性能和太赫兹调制度的影响；在此基础上研究了铁电超晶格在太赫兹频段光电混合调制的性能，研究结果表明泵浦光场和偏置电场不同的调制顺序将产生不同的光生载流子分布以及不同的极化场分布，从而得到抑制调制和促进调制两种不同的结果。 2）基于退火与不退火的铁电薄膜特性研究了基于等离子体诱导透明效应的太赫兹波调制，利用仿真电磁场分布分析了超材料模式之间相消干涉的调控，阐述了非线性太赫兹波调制器动态调制的机理；3）通过对钙钛矿薄膜与钙钛矿薄膜/超材料（PIT）的超快弛豫进行研究，分析了等离子体诱导透明（PIT）的局域场增强效应对整体的弛豫时间的影响，在此基础上研究了钙钛矿的微观驰豫特征及非线性太赫兹波调制的响应机理。4）探究了钙钛矿不同组分对钙钛矿薄膜禁带宽度的影响，研究了匹配可调谐泵浦光的钙钛矿材料，扩展了光泵在太赫兹调制领域的应用范围。在此基础上获得了太赫兹调制度随钙钛矿比例变化的一般规律，为后续太赫兹调制器的研究奠定基础。5）研究了基于 p 型硅雪崩效应的太赫兹调制特性，即在雪崩效应下p 型硅内部的载流子浓度迅速增加，因此可以通过调节器件的电流大小实现对太赫兹波的动态调制。在此基础上研究了基于雪崩效应/等离子体诱导透明（PIT）调制太赫兹波的的微观物理机制。