金属纳米柱的端面修饰对自发辐射增强特性的影响  

Effect of surface modification of metallic nanorod on spontaneous emission enhancement

作　　者：苏玉凤 彭金璋[1] 杨红[1] 黄勇刚[1] Su Yu-Feng;Peng Jin-Zhang;Yang Hong;Huang Yong-Gang(College of Physics and Electromechanical Engineering,Jishou University,Jishou 416000,China)

机构地区：[1]吉首大学物理与机电工程学院,吉首416000

出　　处：《物理学报》2022年第16期301-312,共12页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:11964010,11464013,11464014);湖南省自然科学基金(批准号:2020JJ4495);湖南省教育厅项目(批准号:21A0333);吉首大学研究生科研创新项目(批准号:Jdy20034)资助的课题。

摘　　要：金属纳米柱具有优异的光学性能,其表面等离激元共振可通过纵横比灵活地调节,且能将光场局域到亚波长甚至纳米尺度,被广泛应用于自发辐射调控.然而,当纳米柱的端面形貌和材料不同时,附近量子点的自发辐射特性如何变化尚不明确.本文分别采用经典的德鲁德局域响应近似、非局域流体动力学模型和广义的非局域光响应模型,基于有限元方法,系统地研究金属纳米柱结构的端面形貌、尺寸以及材料对附近量子点自发辐射增强特性的影响.结果表明,当端面形貌由尖端逐渐变为圆柱时,自发辐射增强谱发生明显红移,峰值逐渐增大.相比于金纳米结构,当尖端材料由金改为银时,自发辐射增强谱蓝移,峰值略有降低,而当柱身也改为银时,即全银纳米结构,自发辐射增强谱大幅蓝移,峰值急剧增大.对于两种金属构成的核壳结构,壳层金属对内部金属表面等离激元共振具有屏蔽作用,随着壳层厚度的增大,核壳结构中表面等离激元共振逐渐接近壳层金属表面等离激元共振,对金纳米结构包覆银,共振峰蓝移,而对银纳米结构包覆金,共振峰红移.Metal nanorods show excellent optical properties,since the plasmonic resonance frequency can be tuned by its aspect ratio and the optical field can be confined within a region of sub wavelength,even within a nanometer region.It has the ability to flexibly modify the spontaneous emission properties of a nearby quantum emitter.However,it is unclear how the emission property changes when the metal nanorod has been deposited at the tips or coated on all sides with metal.In this work,the spontaneous emission enhancements of a two-level atom around a tailored nanorod with a wide variety of shapes,dimensions or materials are systematically investigated by the finite element method.Three different optical response models are adopted,including the classical local response approximation(LRA),the nonlocal hydrodynamic model(HDM),and the generalized nonlocal optical response model(GNOR).For a cylindrical nanorod with two endcaps,it is found that the resonance frequency shows large redshift and the emission enhancement peak increases as the endcap gradually changes from cone to cylinder of the same height.The resonance frequency shows small blueshift and the emission enhancement peak decreases slightly as the deposited metal of the conical endcaps changes from gold to silver.However,as the material of the cylinder also changes from gold to silver,becoming an all-silver nanostructure,an obvious blueshift can be detected at the resonance frequency and the emission enhancement peak rises sharply.For bimetal core-shell nanostructure,the shell can screen the surface plasmon of the core from being excited,and the plasmonic resonance associated with shell increases in proportion to the thickness of the shell.The emission enhancement peak for gold nanostructure appears to be blue-shifted when coated with silver.In contrast,it is red-shifted for silver nanostructure coated with gold.

关 键 词：端面修饰 自发辐射 金属纳米柱 

分 类 号：TG14[一般工业技术—材料科学与工程] TB383.1[金属学及工艺—金属材料]