Nano-optics and Near-field Spectroscopy Laboratory, Department of Physics, King's College London , Strand, London WC2R 2LS, United Kingdom.
Sci Rep. 2012;2:829. doi: 10.1038/srep00829. Epub 2012 Nov 20.
Plasmonic technology relies on the coupling of light to surface electromagnetic modes on smooth or structured metal surfaces. While some applications utilise the resonant nature of surface polaritons, others require broadband characteristics. We demonstrate unidirectional and broadband plasmonic antennas with large acceptance angles based on chirped plasmonic gratings. Near-field optical measurements have been used to visualise the excitation of surface plasmon polaritons by such aperiodic structures. These weakly aperiodic plasmonic crystals allow the formation of a trapped rainbow-type effect in a two-dimensional geometry as surface polaritons of different frequencies are coherently excited in different locations over the plasmonic structure. Both the crystal's finite size and the finite lifetime of plasmonic states are crucial for the generation of broadband surface plasmon polaritons. This approach presents new opportunities for building unidirectional, broadband and broad-angle plasmonic couplers for sensing purposes, information processing, photovoltaic applications and shaping and manipulating ultrashort optical pulses.
等离子体技术依赖于光与光滑或结构化金属表面上的表面电磁模式的耦合。虽然一些应用利用表面极化激元的共振性质，但其他应用需要宽带特性。我们展示了基于啁啾等离子体光栅的具有大接收角的单向和宽带等离子体天线。近场光学测量已被用于可视化这种非周期性结构对表面等离子体激元的激发。这些弱非周期性等离子体晶体允许在二维几何形状中形成束缚彩虹型效应，因为不同频率的表面等离子体激元在等离子体结构的不同位置上相干地激发。等离子体状态的晶体的有限尺寸和有限寿命对于宽带表面等离子体激元的产生都是至关重要的。这种方法为用于传感目的、信息处理、光伏应用以及整形和操纵超短光脉冲的单向、宽带和宽角度等离子体耦合器的构建提供了新的机会。
