银纳米一维复式阵列表面等离激元光谱性质

Plasmonic Spectral Properties of Silver Nanoparticles Based 1D Composite Array

纳米尺寸的贵金属在入射光的激发下能够产生表面等离激元效应,即光在金属表面与电子发生耦合,引起金属表面自由电子集体震荡的现象。当自由电子的震荡频率与入射光的频率相同时,可以引起等离激元共振,产生独特的光谱特性。贵金属纳米颗粒的等离激元共振效应在物理、化学、生物等各个领域具有广泛应用。基于银纳米颗粒,提出一种一维复式阵列结构,利用时域有限差分方法研究该贵金属阵列的表面等离激元性质。在该结构中,以SiO_(2)为基底,两种不同的银纳米颗粒沿y轴方向放置在SiO_(2)基底的表面上,形成一维复式阵列,平面波入射光沿z轴负方向垂直入射。实验观察到,在300~1200 nm的波长范围内,该复式阵列结构的表面等离激元能够被有效激发,在其吸收光谱上有两个等离激元共振峰。通过调节该结构纳米颗粒的尺寸、形状和阵列周期等结构参数,等离激元共振峰和电磁场模式均发生有规律的变化。此外,固定其中一个银纳米颗粒不变,改变另一颗粒尺寸,可以发现其吸收曲线的两个共振峰发生不同的变化,结合电场图可以得出两个峰所对应的等离激元共振具有不同的电磁场模式。通过改变其中一个银纳米颗粒的形状,如四棱锥、球体、圆柱体和正方体,可以发现当颗粒形状发生变化时,两个共振峰对应的波长均不发生变化,但是不同颗粒形状所产生的电场分布明显不同,底面处的相对电场强度差别也很明显,依此同样可以验证其吸收曲线存在两个不同电磁场模式的共振峰。研究结果对基于贵金属纳米颗粒阵列结构表面等离激元器件的设计研究工作具有一定意义。

Surface plasmon effects can be induced in nanoparticles of noble metals upon excitation of incident light,in which the light is coupled into free electrons,causing a collective oscillation of free electrons on the metal surface.When the oscillation frequency of free electrons is the same as that of the incident light,surface plasmon resonance may occur.The surface plasmon resonance effect of metal nanoparticles has various applications in many fields,including physics,chemistry,biology,etc.This work proposes a silver nanoparticle-based 1D composite array,and its surface plasmonic properties are investigated via the finite-difference time-domain method.In this structure,SiO_(2) is used as the substrate,and two silver nanoparticles are placed on the surface of the SiO_(2) substrate along the y-axis direction to form a 1D composite array with plane wave incident incident incident vertically along the negative z-axis direction.The results show that the surface plasmons of the 1D composite array are effectively excited in the wavelength range of 300~1200 nm and that two plasmonic resonance peaks are revealed in the light absorption curve.The plasmonic resonances and their associated electromagnetic fields can systematically be tuned by adjusting the structural parameters of the array,including the nanoparticle size,the shape,and the period of the array.In addition,when one silver nanoparticle is fixed,and the size of the other particle is changed,it can be found that the two plasmonic resonance peaks of its absorption curve change differently.Combining the electric field diagrams,the equipartition excitonic resonance correlates to two different electromagnetic modes.By changing the shape of one of the silver nanoparticles,such as a pyramid,sphere,cylinder,orcube,it can be found that when the shape of the nanoparticle changes,the corresponding wavelength of the two plasmonic resonance peaks does not change,but the electromagnetic field distribution generated by different particle shapes is different,and the relative electromagnetic field intensity at the bottom is also significantly different.It can also be verified that the absorption curve has two different electromagnetic field modes.The results indicated in this work are significant in future research on designs of noble metal nanoparticle array-based plasmonic devices.