高耦合强聚焦表面等离激元探针的设计研制与高空间分辨表征

Tip-enhanced near-field optical microscopy is an important method for optical properties characterization of the nano-devices and nano-materials with super-resolution. Nowadays, researches are mostly focused on the direct coupling of the incident light with the tip apex. As a result, the coupling efficiency is relatively low, the local field enhancement is insufficient, and the far-field background noise is rather strong. And these difficulties limit its application in the weak signal detection of the nano-optical field. In this research, we prose to combine the plasmonic structure with the tip, and design a novel plasmonic probe with plasmonic structures fabricated on the shaft or top of the probe to provide the tip with efficient optical field excitation and regulation abilities. Hence, the plasmonic probe is capable of producing extremely strong locally enhanced nano-optical field. The enhancement process owns to the joint effect of surface plasmon and localized surface plasmon effects, resulting in effectively advanced enhancement. Therefore, the local field enhancement and the detection sensitivity of the nano-optical field characterization are significantly improved, based on the field enhancement of the plasmonic probe. In this research, the mechanism of the interaction between the incident optical field and the plasmonic probe will be investigated. The design method of a plasmonic probe will be studied and established. Then the optical responses of a plasmonic probe will be experimentally characterized with near-field optical method. The efficient coupling of the optical field and localized field enhancement based on a plasmonic porbe will be achieved. It will provide theoretical foundation and technical exploration for the development of the tip-enhanced nano-optical field detection method, and effectively advance the characterization techniques of nano-optical field and the nanomaterial’s optical properties.

探针增强近场光学显微术是纳米器件与材料光学特性超分辨表征的重要手段。当前，该技术研究多局限于空间光场与探针尖端的直接耦合增强，致使耦合效率较低、局域增强不足、远场背景噪声强，限制了其在纳米光场微弱信号探测中的应用。本课题旨在将等离激元结构与探针结合，研制一种高耦合强聚焦表面等离激元探针，有效提升探针增强近场光学显微镜的性能。采取的思路是：利用等离激元结构的波矢匹配，获得表面等离激元波的高效激发耦合；基于光场调控作用，使其向探针尖端低损耗定向传播；通过探针结构的相位匹配，在针尖尖端形成局域聚焦增强纳米光场。我们将开展该新型探针的数值模拟设计及其光学响应特性的高空间分辨率表征和光学性能的实验研究，优化表面等离激元探针的设计结构和参数，最终实现具有高效入射光耦合能力和强烈局域电磁场增强作用的表面等离激元探针的研制。为探针增强光谱术、局域等离激元探测、超分辨成像等研究提供重要的理论和关键技术基础。

探针增强近场光学显微术是纳米器件与材料光学特性超分辨表征的重要手段。当前，该技术研究多局限于空间光场与探针尖端的直接耦合增强，致使耦合效率较低、局域增强不足、远场背景噪声强，限制了其在纳米光场微弱信号探测中的应用。本课题旨在将等离激元结构与探针结合，研制一种高耦合强聚焦表面等离激元探针，有效提升探针增强近场光学显微镜的性能。采取的思路是：利用等离激元结构的波矢匹配，获得表面等离激元波的高效激发耦合；基于光场调控作用，使其向探针尖端低损耗定向传播；通过探针结构的相位匹配，在针尖尖端形成局域聚焦增强纳米光场。我们将开展该新型探针的数值模拟设计及其光学响应特性的高空间分辨率表征和光学性能的实验研究，优化表面等离激元探针的设计结构和参数，最终实现具有高效入射光耦合能力和强烈局域电磁场增强作用的表面等离激元探针的研制。为探针增强光谱术、局域等离激元探测、超分辨成像等研究提供重要的理论和关键技术基础。.本项目的研究基本依照研究计划开展进行，通过三年的研究工作，完成了项目计划内容，其中主要包括：（1）等离激元探针结构的原理研究和结构设计，进而基于时域有限差分方法对探针进行电磁场建模和数值模拟，优化了探针结构参数和使用条件；（2）等离激元探针的纳米尺度制备工艺探索，完成了等离激元探针制备；（3）高空间分辨率局域光场的实验表征系统、方法建立和探针针尖附近局域增强光场的探测表征；（4）研究了一种可调控纳米聚焦功能结构，可通过以不同偏振状态入射光激发调控产生的等离激元光场相位，从而实现可通过入射圆偏振光旋向的调控来改变等离激元光场聚焦焦点位置。项目资助发表多篇期刊论文和会议论文，支持核心研究人员的学术成长和研究实习生的培养。