摘要
采用时域有限差分法和麦克斯韦应力张量法,系统研究了金薄膜衬底上介质-金属核壳结构所受的光学力.研究结果表明:由于核壳结构与衬底之间强的等离激元模式杂化效应,其所受的光学力相较于单个核壳结构实现了一个数量级的增强;同时,通过改变激发波长,实现了局域电场分布的调控,以此观察到了核壳结构光学力方向的可控反转;进一步,详细分析了核壳结构所受光学力随其到衬底间距、内核介质的尺寸及折射率等的变化关系,以此丰富了光学力大小、方向和峰值波长的调控方法.研究结果可为精确控制颗粒/金属薄膜纳米腔的尺寸提供一种新的途径,并为调控单分子级的光与物质相互作用、研发新型纳米光子器件提供有益参考.
Manipulating the core-shell structure with the optical force has been extensively studied, giving birth to applications such as particle sorting, biomarkers and drug delivery. Tailoring the optical force exerted on the core-shell above the metallic film remains unexplored, despite the obvious benefits for both fundamental research and applications including strong coupling, surface enhanced spectroscopy, nanolaser, and nanoscale sensing. In this work, we systematically investigate the optical force exerted on a dielectric/metal core-shell above a gold film by utilizing the Maxwell stress tensor formalism. It is found that at the present gold substrate, the optical force on the core-shell can be one order of magnitude larger than that on the individual core-shell due to the strong coupling between the core-shell and the gold film. Interestingly, the direction of the optical force can be reversed from positive to negative by distributing the local field from the upside of coreshell to the structure gap through changing the excitation wavelength. Furthermore, we demonstrate that the magnitude and peak wavelength of the optical force can be well controlled by altering the structure gap, the size and refractive index of the core. More specifically, it is found that the coupling strength between the coreshell and the gold film decreases with the gap size increasing. As a result, we observe the blue shift of bonding mode and the decrease of local field in the gap, which leads the force peak wavelength to be blue-shifted and the force peak magnitude to decrease, respectively. Also, by increasing the radius and refractive index of the core, a red shift of force peak is accompanied with the red shift of the bonding mode. In addition, the force peak magnitude follows the same trend as the total local field enhancement factor when the radius and refractive index of the core change. We hope that our results open the way to control the cavity size of particle on film structure, which would be beneficial for tailoring the light matter interaction even down to single molecular level and promises to have the applications in novel functional photonic devices.
作者
张佳晨
鱼卫星
肖发俊
赵建林
Zhang Jia-Chen;Yu Wei-Xing;Xiao Fa-Jun;Zhao Jian-Lin(Shaanxi Key Laboratory of Optical Information Technology,School of Physical Science and Technology,Northwestern Polytechnical University,Xi’an 710129,China;CAS Key Laboratory of Spectral Imaging Technology,Xi’an Institute of Optics and Precision Mechanics of CAS,Xi’an 710119,China)
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
2020年第18期82-88,共7页
Acta Physica Sinica
基金
国家重点研发计划(批准号:2017YFA0303800)
国家自然科学基金(批准号:11634010,61675170,11874050)
中国科学院光谱成像技术重点实验室开放基金(批准号:LSIT201913W)
中央高校基本科研业务费(批准号:3102019JC008,310201911fz049)资助的课题.
作者简介
通信作者:肖发俊,E-mail:fjxiao@nwpu.edu.cn。
