†School of Physics, Peking University, Beijing 100871, China.
‡State Key Laboratory for Mesoscopic Physics, Peking University, Beijing 100871, China.
Nano Lett. 2015 May 13;15(5):3115-21. doi: 10.1021/acs.nanolett.5b00181. Epub 2015 Apr 7.
Directional light scattering is important in basic research and real applications. This area has been successfully downscaled to wavelength and subwavelength scales with the development of optical antennas, especially single-element nanoantennas. Here, by adding an auxiliary resonant structure to a single-element plasmonic nanoantenna, we show that the highly efficient lowest-order antenna mode can be effectively transferred into inactive higher-order modes. On the basis of this mode conversion, scattered optical fields can be well manipulated by utilizing the interference between different antenna modes. Both broadband directional excitation of surface plasmon polaritons (SPPs) and inversion of SPP launching direction at different wavelengths are experimentally demonstrated as typical examples. The proposed strategy based on mode conversion and mode interference provides new opportunities for the design of nanoscale optical devices, especially directional nanoantennas.
方向光散射在基础研究和实际应用中很重要。随着光学天线的发展，特别是单元素纳米天线的发展，这一领域已经成功地扩展到了波长和亚波长尺度。在这里，通过在单个等离子体纳米天线中添加辅助共振结构，我们证明了高效的最低阶天线模式可以有效地转换为非活跃的高阶模式。在此模式转换的基础上，可以通过利用不同天线模式之间的干涉来很好地控制散射光场。表面等离子体激元 (SPP) 的宽带定向激发和不同波长下 SPP 发射方向的反转都被作为典型实例进行了实验验证。基于模式转换和模式干涉的这种策略为纳米光学器件的设计，特别是定向纳米天线的设计提供了新的机会。
