基于纳米多孔金微结构的光学超材料的可控共振效应研究

Photonic metamaterials are receiving great attention for the purpose of obtaining unique properties and applications, such as invisibility, wave absorbing, which do not exist in natural materials. The applicant has developed a novel electrically controlled metamaterial with tunable optical resonance, and recently they found out that this approach can be applied to nanoporous gold. Nanoporous gold has a similar optical resonance effect which can be controlled by applying external electric signal. However, the trend and underlying mechanism have not been studied yet. Due to both the traditional photonic metamaterials and nanoporous gold have wave absorbing effect, a stronger wave absorbing property can be expected if one can combine them - which means a novel metamaterial based on resonators consisting of nanoporous gold. This study is aiming at exploring the resonance enhancing dependence on ligament size variation, and the mechanism of controlling resonant frequencies and oscillation amplitude under charging condition through the following methods: in-situ electrochemical optical measurement, electromagnetic theory, numerous simulation and so on. By designing the pore size and topology of resonator arrays in metamaterials, the goal of controlling their optical property by electric signal can be achieved. This project is expected to have the following three achievements: 1) understanding the effect of surface charge density of nanoporous gold on its electromagnetic absorption properties; 2) characterizing the novel optical properties and tunability of metamaterials based on nanoporous gold; 3) designing novel functional photonic metamaterials.

为实现天然材料所不具备的性能和在隐身、吸波等方面的应用，光学超材料近年来成为研究热点。申请人曾成功实现了通过电信号调控超材料的共振效应，并于近期发现该方法可应用于纳米多孔金。多孔金具有类似超材料的共振效应且可电信号调控，但其变化规律和机理尚不清楚。由于传统超材料和多孔金都具有吸波效应，如将二者结合，即基于多孔金微结构的新型超材料将会具有更优异的性能。本项目拟通过光度计电化学原位测量和利用电磁场理论、数值模拟等实验和理论研究，探索多孔金随孔径尺寸变化其共振（增强）的变化规律，并研究其在荷电下对共振频率和振幅的调控机理；通过设计微结构阵列的超材料中基础材料的孔径尺寸、和阵列拓扑结构，实现对其光学性能的设计，及在电信号下对共振响应的调控。本研究对揭示多孔金表面电荷密度对电磁波吸收的影响、超材料拓扑结构与图形多孔金的共振的互相耦合对光学性能的复合作用机理、新型超材料功能化设计都将具有重要意义。

为实现天然材料所不具备的性能和在隐身、吸波等方面的应用，光学超材料近年来成为研究热点。纳米多孔金具有类似超材料的共振效应且可电信号调控，由于传统超材料和多孔金都具有吸波效应，如将二者结合，即基于多孔金微结构的新型超材料将会具有更优异的性能。具体总结如下:.(1) 实现纳米多孔金光谱特性的主动调控。通过对纳米多孔金溶液处理、退火、原子层沉积和电化学原位控制等，实现对其光谱特性的调控，发现纳米多孔金韧带尺寸和介质环境的改变都会使其透射光谱谷值偏移，并可实现电信号原位往复调控。.(2) 通过引入长细比和弯曲程度两个参数建立理论模型。其独特的光谱特性表现为550nm左右的透过率谷值和较长波长的透过率峰值，其中前者归因于纳米多孔金等效介电常数实部虚部的同时最大值和趋肤深度的谷值。.(3) 超材料具有明显的尺寸效应。设计和制备了结构单元尺寸分别为1微米和2微米的超材料，结构单元尺寸不同其响应波段也不同。.(4) 结构单元材料分别为纳米多孔金和纯金的超材料，其在红外波段的光谱响应特性相似。主要在于光谱响应特征波长的差别，主要是由于纳米多孔金的相对密度较低，性能更好。.(5) 设计并制备了结构布局分别为网状结构和方形阵列的结构单元互补超材料，实验和模拟结果吻合良好并发现：无论结构单元是纳米多孔金还是金，相同尺寸两种结构的超材料响应特征基本一致。. 本项目通过原位实验和理论、数值模拟等方法，探索多孔金随孔径尺寸变化其光谱特性的变化规律，并研究在电信号作用下对其共振频率和振幅的调控机理；通过设计微结构阵列的超材料中基础材料的孔径尺寸、和阵列拓扑结构，实现对其光学性能的设计。本研究对揭示多孔金表面电荷密度对电磁波吸收的影响、超材料拓扑结构与图形多孔金的共振的互相耦合对光学性能的复合作用机理、新型超材料功能化设计都将具有重要意义。