基于强色散表面波耦合的表面等离激元电子间接耦合激发的探索

Using the graphene surface plasmon polaritons (SPPs) excited by electrons to generate radiation waves is one of the latest trends of terahertz sources. However, there are still many shortages of the current methods of the electron excitation of SPPs. In this project, the graphene based hyperbolic medium and the spoof surface plasmon polartions (SSPs) excited by electrons are innovatively used to improve the electromagnetic properties of SPPs and the source fields of the excitation, respectively. And then SPPs are mediated excited by the coupling between the dispersive SSPs and SPPs. Compared with current methods, there are many advantages of low propagation loss, coherence, wide bandwidth and large power density for mediated coupling excitation. Theoretical analyses and computer simulation are planned to study the physical mechanism. By solving the scientific questions of optimization of SPPs, strong interaction between electrons and SPPs with high confinement factor, and the efficient coupling between the dispersive SSPs and SPPs, the coherent and tunable excitation scheme with beam voltage lower than 10 kV, center frequency in 4~10 THz, tuning bandwidth larger than 500 GHz is planned to be designed, and validated by the principle experiment. This project is viable for the results of the pre-studied related theoretical and experimental analyses, and more than 20 papers have been published. Accordingly, this project is of great significance of the development of terahertz radiation sources.

利用自由电子激发石墨烯表面等离激元(SPPs)是当前太赫兹源研发的新趋势之一，但现有SPPs电子激励方法仍有诸多不足。本项目创新性地使用石墨烯-介质双曲材料改善SPPs电磁特性；利用自由电子激发仿表面等离激元(SSPs)改善源场特性；通过强色散表面波相互耦合间接激发SPPs。较现有方式，本方案具有传播损耗低、相干性强、调谐带宽大及功率密度高等优势。本项目拟通过理论分析、计算机仿真等手段研究相关物理机理，解决改善SPPs电磁特性、保证自由电子与SSPs高效相互作用以及保证强色散SPPs、SSPs间高效耦合等科学问题，设计工作电压10kV以下，中心频率4~10THz，调谐带宽500GHz以上的强相干、连续可调的SPPs激励方案，并展开相关原理验证实验。项目组前期展开了详细研究，发表SCI论文20余篇，具有丰富的相关实验经验，具备可行性。综上，本项目对推进太赫兹源的发展具有重要意义。

本项目面向多层石墨烯双曲材料SPPs层间耦合、间接耦合激发等科学问题开展研究。完成了石墨烯双曲材料中SPPs色散特性、传播特性、功率分布、高局域因子SPPs与石墨烯SPPs相互作用等理论模型研究，设计了基于周期性人工微结构阵列与激光泵浦多层石墨烯双曲材料间接耦合激发SPPs的太赫兹放大结构，并完成相关原理验证实验。基于上述成果，本项目进一步开展了基于SPPs层间耦合、间接耦合的太赫兹开关、高速调制器等器件的设计、加工、测试工作。研制出基于层间耦合的动态共面光栅太赫兹传输线，具有大宽带、低群时延的特定；研制出基于间接耦合的插入损耗优于1dB的太赫兹开关；研制出基于层间耦合的太赫兹高速直接调制器，单通道调控速率突破30Gbps。