低损耗表面等离子晶体自准直效应研究

Plasmonic crystal with periodic metal structures has self-collimating (SC) effect which has been found in photonic crystal. It can control light propagation with no divergence in sub-wavelength space, and has potential applications in on-chip interconnected for very large photonic integrated circuits (photonic VLSI). Until quite recently, it has attracted researchers' attentions. However, the strong absorption of light in metal decreases the performance of surface plasmon polariton (SPP) devices severely. In this project, long-range SPP （LRSPP） and hybrid photonic-plasmonic (HPP) structures are used to reduce the transmission loss, and plasmonic cystal with low-loss SC effect will be designed and realized. Comparing with the SPP SC effects which have been reported, the SC effect in LRSPP and HPP structures has two advantages: 1) Introducing low-loss SC SPP propagation into telecommunication bands based on the works which have done in terahertz and microwave bands. This is important for on-chip photonic communications in the future; 2) Point out that loss is the critical limitation of using SPP SC effect in the photonic integrated circuits, develop low-loss SC effect in plasmonic crystal and enhance the SC propagation length. The study of low-loss SC effect in plasmonic crystal not only has high academic value, but also has has practical significance in sub-wavelength optical wave manipulating and device interconnections in future photonic VLSI.

基于周期性金属结构的表面等离子晶体具有与光子晶体类似的自准直效应，能够在亚波长尺度上限制光束在特定方向传播而不发生扩散，在未来大规模光子集成回路存在广阔的应用前景，最近刚刚引起学术界的重视。然而, 金属对光波的固有吸收严重增加了基于表面等离子晶体自准直效应器件的损耗。本项目拟采用长程表面等离子激元和混合表面等离子激元两种结构降低传输损耗，实现支持长距离自准直传播的表面等离子晶体。同已有的研究相比，本项目的创新点在于：1）首次研究通信波段低损耗表面等离子晶体自准直效应，对光子通信具有更现实的意义；2）提出损耗是限制表面等离子激元自准直效应应用的关键因素，提出了两种低损耗结构，有效增加自准直传播距离。这一研究开辟了自准直效应研究新的研究方向，不仅有重要的学术价值，同时为未来突破衍射极限的光束控制、器件互连提供了解决方案，在大规模光子集成回路领域具有更重要的应用价值。

基于微纳光子器件实现的光学自准直效应，能够在亚波长尺度上限制光束在特定方向传播而不发生扩散，在未来大规模光子集成回路中具有广阔的应用前景。本项目开展了基于混合光子-等离子晶体结构的光学自准直效应的理论与实验研究；研究了硅基条形波导与缝隙波导的色散、模场分布等光学特性与波导结构参数的关系；提出了两种低损耗混合光子-等离子体波导，研究了其传播长度与模场尺寸等特性；设计并优化了两种类型自准直晶体结构；通过网格划分和吸收边界优化设计，实现了高色散材料周期性结构分析算法的快速收敛；利用FDTD法，研究了混合光子-等离子晶体的色散关系及等频线变化规律，实现了宽带范围内的光学自准直效应；通过改变材料折射率，实现了自准直角度的连续可调；设计优化了交叉波导、基于微环谐振腔的光开关及M-Z干涉仪等微纳器件；基于耦合模理论及周期性波导下的模式转换理论，研究了模式转换效率与光波导截面折射率分布的关系，提出了一种计算片上模式转换器尺寸理论极限的方法。该项目的研究开辟了自准直效应研究的新方向，不仅具有重要的学术价值，同时为未来突破衍射极限的光束操控、器件互联等提供了解决方案，在大规模光子集成回路领域具有更重要的应用价值。

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