基于硅纳米粒子-光子晶体纳腔复合结构的亚波长尺度光场调控

Controlling of sub-wavelength light-field is of great significance for accurately constructing novel light-fields, efficiently controlling light-matter interactions, and miniaturizing optical devices. Unfortunately, diffraction limit of light-field makes it difficult to implement the controlling of sub-wavelength light-field. This project proposes to construct a composite structure of a planar photonic crystal nanocavity and a silicon nanoparticle nanocavity, which could provide a platform to study the controlling of sub-wavelength light-field and its far-field scattering. The sub-wavelength resonant modes in the planar photonic crystal nanocavity and plentiful electromagnetic modes in the silicon nanoparticle nanocavity would strongly facilitate the light-field controlling in the composite structure. To achieve these, following major studies will be carried out: (1) Mode-couplings of the sub-wavelength resonant modes in the two nanocavities, as well as the derived novel light-field modes; (2) Modulations of phases and polarizations in the far-field scattering light; (3)As an example, constructing a circularly polarized light-field. Three key scientific problems are required to be solved: (1) Coupling model of the two nanocavities; (2) Determinations of effective dielectric constant and permeability of silicon nanoparticles with different Mie resonances; (3) Precise controllings of phases and polarizations in the far-field scattering light. The novelties of this proposal include: (1) Achieving efficient and precise controllings of the sub-wavelength light-field relying on the couplings between resonant modes of the two nanocavities; (2) Controlling light-field from a new view of modulating its magnetic component with the assistance of the high magnetic permeability of the magnetic dipole in the silicon nanoparticle; (3) Constructing plentiful far-fields by only controlling a sub-wavelength mode based on the multi-degree-of-freedom controllable far-field scattering of the silicon nanoparticle. The results obtained from above studies are expected to not only provide a novel photonic structure for multi-dimensional precise controlling of sub-wavelength light-fields, but also present a routing to miniaturizing and integrating optical devices with functionalities of light-field controlling.

亚波长尺度光场的调控对精准构建新型光场、高效控制光与物质作用、微型化光学器件均有重要意义，但光衍射极限使其实现存在挑战。本项目拟借助平板光子晶体纳腔的亚波长尺度模场和硅纳米粒子腔的丰富电磁模式，通过构建两个纳腔的复合结构，调控亚波长尺度模场及其远场散射。主要研究：①亚波长尺度模场的耦合及衍生的新颖光场模态；②远场散射相位、偏振等的调控规律；③作为案例，构建圆偏振光场。拟解决关键问题是：①两个纳腔的耦合模型建立；②不同Mie共振下硅纳米粒子有效介电常数和磁导率的确定；③远场散射相位和偏振的精准控制。创新点有：①通过纳腔间共振模耦合，高效精准调控亚波长尺度光场；②借助硅纳米粒子中磁偶极子的高磁导率，从磁场角度调控光场；③基于硅纳米粒子多自由度可控的远场散射，仅调控亚波长尺度模场便可构建丰富远场。研究成果有望为亚波长尺度光场多维度精准调控提供新颖光子结构，也为光场调控器件微型化和集成化提供思路。

亚波长尺度光场的调控对精准构建新型光场、高效控制光与物质作用、微型化光学器件均有重要意义，但光衍射极限使其实现存在挑战。本项目拟借助平板光子晶体纳腔的亚波长尺度模场和硅纳米粒子腔的丰富电磁模式，通过构建两个纳腔的复合结构，调控亚波长尺度模场及其远场散射。项目从不同新型光子晶体纳腔的设计、纳米粒子腔与平板光子晶体纳腔构成的复合纳腔上模场耦合规律阐明、新颖亚波长尺度光场模态的揭示、复合结构上远场散射的调控均取得进展，达到了预期目标。. 取得的结果有：①为了选择合适的平板光子晶体纳腔，深入研究了几种二维光子晶体以及光子晶体纳腔的电磁模式、光谱特征、品质因子、模式体积、以及Purcell效应等；设计了新型的平板光子晶体纳腔，包括“切孔型”平板光子晶体纳腔以及拓扑光子晶体腔，为亚波长尺度光场调控提供了更优的纳腔结构；②为了获得新型的高品质因子纳米粒子结构，分别研究了金开口环、硅纳米球、纳米线、纳米粒子链波导以及硅基超表面等一系列光学纳腔器件；基于Mie散射理论，设计了一系列与平板光子晶体纳腔具有良好耦合效果的纳米粒子腔（包括金开口环、硅纳米球）与纳米尺寸的片上激光器（可实现单模激光的超小尺寸纳米线）；③进一步，构建了硅纳米粒子腔与平板光子晶体纳腔之间的耦合模型；计算了不同尺寸的硅纳米粒子腔与平板光子晶体纳腔耦合的强弱，分析了耦合模式的不同。④结合以上研究内容，将具有强局域特性的金开口纳腔以及硅纳米粒子与平板光子晶体纳腔集成，在亚波长尺度实现了磁模式响应的片上激发、调制以及偏振可调的矢量光场激发，有效调控了平板光子晶体纳腔模场（包括近场与远场）。. 研究成果有望为亚波长尺度光场多维度精准调控提供新颖光子结构，也为光场调控器件微型化和集成化提供思路。

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