简介: |
Abstract:
With the advantage of tight field confinement, nanophotonic devices based on surface plasmons (SPs) are widely explored, which can break the diffraction limit of light and make more compact integration in nanophotonic circuits. Chemically synthesized Ag nanowires (NWs) are excellent waveguides that support propagating SPs. Recently, we have shown that the local electric field distribution of propagating SPs along Ag NWs can be imaged by coating the NWs with a layer of quantum dots with Al2O3 as spacer layer. This provides a valuable tool for the study of SPs propagating along NW waveguides. The superposition of different plasmon modes excited in the NWs makes the near field distribution modulated and show quasi-periodic beating pattern. The near field distribution patterns depend strongly on the polarization and phase of the input light which can be used to realize a complete family of optical Boolean logic gates in simple nanowire networks. We further demonstrated that a plasmonic binary NOR gate, one of the so-called “universal logic gates”, can be realized through cascaded OR and NOT gates in four-terminal plasmonic NW networks].
The surface plasmons in Ag NWs depend strongly on the dielectric surroundings. In a uniform embedding medium, the plasmons propagate helically around the nanowire with the handedness determined by the polarization of the excitation light. By changing the thickness of the coated Al2O3 layer on the NW, we systematically investigate the period change of the near field pattern. The results show that the period is quite sensitive to the change of the coating thickness. The mechanism is revealed by considering the propagation constants and dispersion relations of different plasmon modes. Since the near field distribution plays a critical role in determining the SP transmission in nanowire networks, the control to the SP near field will benefit the design of plasmonic devices. In addition, we have made a theoretical study of the properties of SPs in a metallic nanowire over substrate (NWOS) configuration. The dielectric substrate breaks the symmetry of the system and mediates the coupling of different primary wire plasmons. For NWOS with a high-permittivity substrate, leaky radiation into the substrate raises the propagation losses so that the propagation distance is shorter in the longer wavelength region. By simply adding a high-permittivity layer onto the low permittivity substrate, we show that leaky radiation can be blocked and high-performance plasmonic waveguiding can be extended to the near-infrared region.
CV
徐红星的主要研究集中在表面增强光谱和金属纳米结构的等离激元光子学（Plasmonics）特性，主要成果包括：发现金属纳米间隙结构的极强电磁场增强效应是产生单分子灵敏度的表面增强拉曼光谱的原因，在理论上系统地研究了单分子表面增强拉曼光谱的机理及产生条件；论证了利用表面增强光学力进行单分子捕获的可行性；提出了表面增强拉曼与表面增强荧光的统一理论；系统研究了金属纳米间隙结构的表面增强拉曼光谱和激光偏振方向的关系；发现金属纳米结构作为纳米天线可以旋转单分子拉曼散射的偏振方向；实现了表面增强拉曼散射的远程激发；自主研发了高真空针尖增强拉曼光谱系统，观察到了有机小分子红外活性模式的拉曼增强，并发现了表面等离激元诱导的有机分子化学反应；系统地研究了银纳米线波导中等离激元的激发、传播和发射特性，并揭示其主要机理；利用金属纳米波导网络中等离激元的特性，研制出纳米光子路由器、完备的纳米全光逻辑器件和半加器；通过单元器件或门和非门的级联实现了或非运算等。发表相关论文120余篇，被SCI杂志他引4400余次，在以他为第一作者的研究工作中，单篇最高被SCI杂志引用1050余次，次高750余次。 |
