基于矢量涡旋光场的表面等离激元Fano共振的动态调控及应用

Plasmonic Fano resonance originates from the coupling between the superradiant and subradiant modes in metallic nanostructure. It features with varieties of unique characteristics, such as the dramatically enhanced local field and the tunable spectral lineshape, which suggest the promising applications of Fano resonance in bio-sensing, optical switching, and surface-enhanced Raman scattering (SERS). In this project, we propose a new scheme to coherently control the interference channel between the superradiant and subradiant modes by employing the reconfigurable vectorial vortex beam as excitation. It is intended to achieve controllable Fano lineshape as well as the corresponding local field, which are further demonstrated the applications in the enhanced nonlinear optical effects. The research contents include: ① the mechanisms for exciting and manipulating the superradiant and subradiant modes with the vectorial vortex beam; ② the fundamental physics of the coherent coupling between the superradiant and subradiant modes under the illumination of the vectorial vortex beam; ③ the method for probing the local field intensity under Fano resonance basing on SERS; ④ the strategies for enhancing and modulating the second harmonic and sum-frequency generation of plasmonic Fano structures with the vectorial vortex beam. Our research can promote the applications of Fano resonance in the novel nanophotonic devices for optical switching and frequency conversion, and could be beneficial for the investigations of the quantum state manipulation and quantum interference effects in mesoscopic systems.

表面等离激元Fano共振源于金属纳米结构中超辐射和亚辐射模式的相干耦合。它具有显著的局域场增强效应和可控的光谱线型，因而在生物传感、光开关、表面增强拉曼散射等方面展现了巨大的应用价值。本项目基于光场调控的原理，通过裁剪矢量涡旋光场的相位与偏振态分布，操控超辐射和亚辐射模式的激发与耦合，实现Fano共振光谱线型和局域场强度的灵活、动态调控，并进一步探索调谐Fano共振在非线性光学增强效应方面的应用。具体研究内容包括：①矢量涡旋光场对局域表面等离激元超辐射、亚辐射模式的激发与调控机制；②矢量涡旋光场对超辐射和亚辐射模式相干耦合过程的调控机制；③基于表面增强拉曼散射的Fano共振局域场强度的探测方法；④基于矢量涡旋光场的Fano共振结构二次谐波及和频信号的增强与调控方法。本项目的研究有望拓展Fano共振在光开关、频率转换等纳米光子器件方面的应用，并为介观体系中量子态操控、量子干涉等研究提供借鉴。

表面等离激元Fano共振源于金属纳米结构中超辐射和亚辐射模式的相干耦合。它具有显著的局域场增强效应和可控的光谱线型，因而在生物传感、光开关、表面增强光谱等方面展现了巨大的应用价值。本项目基于光场调控的原理，通过裁剪矢量光场的相位与偏振分布，操控表面等离激元模式的激发与耦合，实现Fano共振光谱线型和局域场强度的灵活、动态调控，并进一步探索调谐Fano共振在非线性光学增强效应方面的应用。具体研究内容包括：①通过裁剪矢量光场的偏振态分布、石墨烯的费米能级、结构的几何参数等，实现了等离激元法诺共振光谱线型的调控和局域场的进一步增强；②调节矢量光场的偏振态分布，实现了等离激元模式的选择性激发及模式耦合的有效操控，进一步实现了远场辐射的单向性，并拓展了其在纳米位移传感方面的应用；③利用矢量光场激发了等离激元纳米腔中的暗模式，并利用该模式的强局域场实现了纳米级介质颗粒的稳定捕获，以及纳米颗粒光学力方向的可控切换；④以矢量光场为激发光，在Fano共振结构中实现了二次谐波50倍的增强和峰值波长近400nm的调节。从基础层面讲，本项目的研究结果有助于加深对表面等离激元模式间耦合规律（特别是复杂高阶模式）的认识，并为原子、分子体系中轨道杂化、量子干涉等的研究提供新的思路；从应用角度讲，掌握对Fano共振光谱线型的裁剪技术，可以改善其在生物传感、光开关、纳米颗粒光操控、精密位移传感等方面的性能；同时，通过Fano共振的局域场强度、模体积的优化，可以显著提高许多光学过程（如拉曼散射、荧光、二次谐波）的效率，推动单分子检测、光学频率转换等技术的进步。