碳基复合结构等离激元波导的构建与特性调控研究

Nanophotonic waveguides based on surface plasmon polaritons (SPPs) have been recognized as an essential component for realizing optical integrated circuit beyond the diffraction limits. Previous studies have showed that designed noble metal waveguides were intrinsically difficult to work in the sub-wavelength range, because of the high impedance of metal nano-structures and non-tunable resonant frequency. On the other hand, graphene plasmons has superior properties that could overcome these obstacles due to the extremely high quantum efficiency for light-matter interactions. Furthermore, graphene plasmon can be modulated by gating, doping and other chemical means, a property that are not achievable for conventional plasmonics based on noble metals. We propose to use graphene nanoribbon with/without noble metals to construct various waveguide structures. Then we will detailed analyze the correlation between physical parameters of plasmon transmission, including the electrical field intensity distribution, the phase delay, polarization dependence, and the waveguides geometry, such as its chiral boundary and the composite structure. We will investigate the basic physical mechanism of plasmon transmission in nanoscale carbon-based waveguide devices. This proposal described a fundamental research of carbon-based material plasmons and its propagation/coupling mechanism, which will provide the theoretical and experimental basis for achieving nanophotonic waveguide for photonic integration circuit.

基于表面等离激元（SPPs）的波导器件是在亚波长范围实现光子集成电路的关键元件之一。目前受到广泛关注的贵金属材料SPPs波导具有传输损耗大和方向不易控制等技术问题,与其相比，石墨烯等离激元具有模式可调、传输阻抗低等优异特性，被认为是有望解决以上问题的新型波导材料。本申请项目拟研究石墨烯以及石墨烯/贵金属复合材料构筑的波导结构中等离激元传输行为及其基本物理机制，通过近场光学探测等相关实验技术及理论模拟详细分析等离激元传输中的场强分布、相位延迟和偏振变化等物理参量与波导结构的几何尺寸、边界手性、介质环境的依赖关系，实现对碳基等离激元纳米波导的性质调控，建立低维碳材料等离激元波导耦合的物理模型。本项目工作是碳基纳米材料在等离激元波导传输中应用的基础研究，为其在微纳光子集成领域内的提供理论依据和实验基础。

由于石墨烯中载流子的Dirac费米子特性，石墨烯等离激元具有高的光场局域、低本征衰减和电学动态可调等优异的性质，是实现有源纳米波导器件的重要手段。本项目采用理论和实验相结合的方式系统研究了石墨烯等离激元的波导特性，主要取得以下四个方面的进展：（一）建立了石墨烯等离激元的物理模型及其影响机制。通过改变石墨烯等离激元微结构的几何尺寸、石墨烯的缺陷密度、基底介电环境等，建立了石墨烯等离激元在不同环境下的色散关系。研究结果表明由于石墨烯的单原子层特性，其等离激元极易受到基底介电环境的影响，特别是基底声子与石墨烯等离激元的强耦合作用和杂质电荷对石墨烯等离激元的散射。等离激元-声子的耦合会影响等离激元的共振频率、模式分布、电学可调性、传播长度等基本性质；杂质电荷的散射会引起等离激元的能量衰减。（二）设计了基于石墨烯/单层氮化硼异质结构的等离激元-声子极化波杂化激元波导结构，并建立了相关的理论模型。该杂化激元模式结合了等离激元模式强场增强和声子极化波模式低衰减的优点。（三）研究了石墨烯/贵金属复合材料构筑的波导结构中等离激元的传输行为，并设计了两种新型复合结构用于提高石墨烯波导的集成密度和局域光场强度。（四）基于所获得的高性能石墨烯等离激元波导器件-具有高的光场压缩和局域光场增强，我们实现了纳米物质的红外光谱增强探测。经过该项目的研究，我们建立了石墨烯等离激元波导的物理模型，并设计了一种杂化激元波导结构和两种复合波导结构，为石墨烯离激元波导结构在微纳光子集成领域内的应用提供了理论依据和实验基础。