太赫兹石墨烯超材料电磁特性的超快响应机理及功能器件研究

Tunable terahertz metamaterials with predominant electromagnetic properties have attracted considerable domestic and foreign attentions. However, the applications of ultrafast electromagnetic properties and development of ultrafast functional devices based on the tunable terahertz metamaterials are severely restricted due to low mobility and complex structure of active materials. This project firstly utilizes ultrafast relaxation nonequilibrium carrier from ultrafast pumped graphene, enabling to ultrafast modulate terahertz wave, to structure a novel ultrafast modulation metamaterial. The coupling conductive mechanisms and relaxation channels between ultrafast relaxation nonequilibrium carrier and unit cell are investigated by the ultrafast-pumped and terahertz-proped technology. The ultrafast relaxation models are established to provide the theorical evidences realizing terahertz metamaterials with ultrafast modulation. The ultrafast change regulations in electromagnetic properties of ultrafast-pumping metamatrials are investigated numerically and experimentally, optimizing structures and performances of ultrafast metamatrials, as a result, building design rules and procedures of ultrafast metamatrials. On this basis, the ultrafast terahertz switches and near-field modulator based on the ultrafast electromagnetic of terahertz graphene metamaterials are further explored to provide new idea in design and development of ultrafast devices. Therefore, this project has very important theory and the practical significance in promoting the development of ultrafast modulation metamatrials and devices.electromagnetic properties of ultrafast-pumping metamatrials are investigated numerically and experimentally, optimizing structures and performances of ultrafast metamatrials, as a result, building design rules and procedures of ultrafast metamatrials. On this basis, the ultrafast terahertz switches and near-field modulator based on the ultrafast electromagnetic of terahertz graphene metamaterials are further explored to provide new idea in design and development of ultrafast devices. Therefore, this project has very important theory and the practical significance in promoting the development of ultrafast modulation metamatrials and devices.

可调谐太赫兹超材料以其优越的电磁性能引起国内外广泛关注，然而由于所用的活性材料载流子迁移率低和结构复杂等原因，严重制约可调谐太赫兹超材料的超快电磁特性的应用及超快功能器件的开发。本课题首次采用超快泵浦石墨稀产生的超快驰豫非平衡载流子（载流子迁移率约为硅的3倍）超快调制太赫兹波的方法来构建一种新型可超快调制的超材料。利用超快泵浦太赫兹探测技术研究超快泵浦下石墨烯非平衡载流子与超材料结构单元的耦合传导机制以及驰豫通道，并构建超快驰豫模型，为太赫兹超材料实现超快调制提供理论依据；数值和实验研究超快泵浦下超材料电磁特性的超快变化规律，并优化结构和性能，进而构建超快超材料的设计规则和流程；在此基础上，探索基于太赫兹石墨烯超材料超快电磁特性的超快太赫兹开关和超快近场调制器，为超快器件设计和开发提供新思路。因此，本项目的研究对促进超快调制的超材料及其器件发展具有重要的理论和实际意义。

针对当前太赫兹超材料的超快电磁响应特性受半导体或超导体等活性材料的载流子迁移率低、制备工艺复杂、驰豫时间长等因素限制，本项目突破传统太赫兹超材料电磁特性超快调制的思维方式，从超快泵浦后活性材料非平衡载流子的超快驰豫机理出发，研究了原位直接生长石墨烯工艺参数及其性能表征，并根据Kubo公式提出了石墨烯太赫兹电导率模型和介电常数模型，构建了基于石墨烯结构和石墨烯-金属交叉的可调谐太赫兹超表面，揭示了石墨烯静态调制电磁特性机理；在此基础上，利用超快泵浦太赫兹探测系统研究石墨烯薄膜和石墨烯超材料的超快电磁特性，揭示了石墨烯薄膜和石墨烯超材料的超快驰豫机理，并制备和开发出具有模式转换、幅度调制以及开关等功能的太赫兹超快功能器件。因此，本项目的研究成果解决了现有超快调制太赫兹超材料结构复杂、超快驰豫慢、制备工艺繁琐以及难以有效控制等缺陷，对促进新型的、高性能的太赫兹超快功能器件的开发和应用具有重要的理论和实际意义。