基于近场相位调控的高分辨定向色彩路由

Near-field optical phase manipulation can drive negative refraction at optical frequencies, plasmonic analogies of electromagnetically induced transprency, and Fano resonances. Recently, it was reported that the gold and silver bimetallic nanoparticles demonstrated the subwavelength directional color routing (DCR) by tuning the optical phase. In order to explore the novel scheme of DCR and further improve the resolution, this project plans to study the near-field phase evolution, the wavelength tunability, and the polarization dependence of plasmonic double dark resonances. Based on the double dark (or quasi-dark) resonance with a narrow linewidth coupled into the single bright resonance with a broad linewidth,giving rise to a sudden change in optical phase, the two-channel DCR can work within the linewidth of the bright-mode resonance. According to this scheme, the resolution can be improved to be less than 50 nm, and the tunability of wavelength and polarization can be achieved, while the gold and silver bimetallic nanoparticles only can distinguish the red light from the blue one (i.e., a resolution of 150 to 200 nm). With the aid of the FDTD calculations, the UV photolighography, and the leakage radiation spectroscopy, the properties of directional color routing originating from the plasmonic double dark resonances will be studied theoretically and experimentally. The dependences of the phase evolution on wavelengths, angles of the two-channel directional scattering, and incident polarizations will be elucidated, which paves the way for on-chip optical communications.

近场光学相位调控可驱动光频区负折射、等离子体诱导电磁感应透明和Fano共振等物理效应，最近有研究显示在金、银纳米颗粒对阵列中进行相位调控可实现亚波长双通道定向色彩路由。为进一步探索新型定向色彩路由策略，提高路由分辨率，本项目计划研究等离子体双暗态共振的近场相位变化规律，波长可调特性及偏振依赖性。利用暗态共振线宽窄的特点与宽线宽的亮态共振耦合形成相位突变，从而将双通道分辨波长限制在亮态线宽内，使双通道定向色彩路由的分辨波长从仅能区分蓝光和红光（分辨率约150～200纳米）提高至50纳米以内，并进一步实现波长和偏振可控。通过FDTD设计、紫外光刻制备和搭建的leakage radiation光谱成像探测等理论和实验手段，系统研究基于等离子体双暗态共振的双通道定向色彩路由特性，揭示双暗态相位变化与双通道定向色散波长、角度和入射偏振之间的相互关系，旨在为片载光信号传输提供有力的支持。

近场光学相位变化是驱动光频区负折射、定向单光子源、等离子体诱导电磁感应透明和Fano共振等效应的重要物理机制，最近有研究显示通过对金、银纳米颗粒对进行相位调控可获得亚波长双通道定向色彩路由特性，但在频段选择、分辨率、偏振控制上具有一定局限性。本项目具体研究了在太赫兹频域双暗态共振效应的太赫兹波近场分布，传播行为和频率分辨特性，理论上展示了利用基于双暗态共振效应的太赫兹超材料可实现将两个频率差为0.2 THz的电磁波导向不同方向，实现定向散射路由。我们利用紫外光刻技术在柔性衬底上制备出了高质量的超材料，将进一步利用近场太赫兹探测技术实现太赫兹定向散射路由的实验验证，旨在为片载电磁信号传输提供有力支持。