Enhancement of local electric field in core-shell orientation of ellipsoidal metal/dielectric nanoparticles

Ismail Ismail,Gholap Gholap,Abbo Abbo

doi:10.5488/cmp.20.23401

Abstract

In this paper it is shown that the enhancement factor of the local electric field in metal covered ellipsoidal nanoparticles embedded in a dielectric host matrix has two maxima at two different frequencies. The second maximum for the metal covered inclusions with large dielectric core (small metal fraction $p$) is comparatively large. This maximum strongly depends on the depolarization factor of the core $L_{z}^{(1)}$, keeping that of the shell $L_{z}^{(2)}$ constant and is less than $L_{z}^{(1)}$. If the frequency of the external radiation approaches the frequency of surface plasmons of a metal, the local field in the particle considerably increases. The importance of maximum value of enhancement factor $|A|^{2}$ of the ellipsoidal inclusion is emphasized in the case where the dielectric core exceeds metal fraction of the inclusion. The results of numerical computations for typical small silver particles are presented graphically.

Highlights

The enhancement of the local electric field of the incident electromagnetic radiation in the composites of metal covered nanoparticles with dielectric core is of great importance due to different possible applications such as surface enhanced Raman spectroscopy [1], metal enhanced florescence [2], quantum electrodynamics [3, 4], nonlinear optical effect [5], quantum optomechanics [6], optical sensors [7] and nano-optical tweezers [8]
It is known that the local electric field in the inclusions can be considerably enhanced if a frequency of the incident radiation is close to the surface plasmon frequency [9]
Where the subscript “m” indicates pure metal inclusion. We present this quantity versus z, and one can see that the enhancement factor | Am|2 in the physically interesting range of parameters sharply depends on the frequency of an incident electromagnetic wave ω and weakly depends on the depolarization factor decreasing with L

Summary

Introduction

The enhancement of the local electric field of the incident electromagnetic radiation in the composites of metal covered nanoparticles with dielectric core is of great importance due to different possible applications such as surface enhanced Raman spectroscopy [1], metal enhanced florescence [2], quantum electrodynamics [3, 4], nonlinear optical effect [5], quantum optomechanics [6], optical sensors [7] and nano-optical tweezers [8]. It is known that the local electric field in the inclusions can be considerably enhanced if a frequency of the incident radiation is close to the surface plasmon frequency [9]. At present, such fields may be achieved by laser radiation Another interesting property of a pure metal and metal-covered dielectric small particles is an abnormal enhancement of the local field, when the frequency of the incident electromagnetic wave approaches the surface plasmon frequency of the metal [12].

Electric potentials distribution in a coated ellipsoidal metal nanoparticle

Numerical results and discussion

Conclusion