scholarly journals Plasmonic Modes and Optical Properties of Gold and Silver Ellipsoidal Nanoparticles by the Discrete Dipole Approximation

2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
Mohammed Alsawafta ◽  
Mamoun Wahbeh ◽  
Vo-Van Truong
Keyword(s):  
Principal Axis ◽  
Length Distribution ◽  
Longitudinal Mode ◽  
Specific Rotation ◽  
Dipole Approximation ◽  
Absorption Efficiency ◽  
Discrete Dipole Approximation ◽  
Band Position ◽  
Principal Axes ◽  
Axis Length

The discrete dipole approximation (DDA) is used to model the absorption efficiency of isolated gold (Au) and silver (Ag) ellipsoidal nanoparticles. The characteristics of the plasmonic bands of those nanostructures depend strongly on the size and orientation of the particles in both the lab and target frames. At specific rotation and incident angles, the desired plasmonic mode can be excited. The result of the simulation shows the possibility of excitation of three plasmonic modes—one longitudinal mode (LM) and two transverse modes (TM)—corresponding to the redistribution of the polarization charges along each principal axis. At oblique incidence of the incoming light, both the Au LM and a hybrid Au TM are observed whereas three more distinct plasmonic modes can be found in the case of the Ag particle. The effect of length distribution on the characteristics of the plasmonic bands is also examined for the three principal axes. The band position of the plasmonic bands associated with the electronic oscillation along each principal axis is found to vary linearly with the axis length. The linear variation of the band position of the LM is steeper as compared with the one found for the other modes.

scholarly journals Simulated Optical Properties of Gold Nanocubes and Nanobars by Discrete Dipole Approximation

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Mohammed Alsawafta ◽  
Mamoun Wahbeh ◽  
Vo-Van Truong
Keyword(s):  
Absorption Spectrum ◽  
Cross Section ◽  
Longitudinal Mode ◽  
Transverse Mode ◽  
Dipole Approximation ◽  
Discrete Dipole Approximation ◽  
Absorption Cross ◽  
Extinction Cross Section ◽  
Band Position ◽  
Mode Tm

The absorption spectra for a gold nanocube and for a gold nanobar are calculated by using the Discrete Dipole Approximation (DDA). The results show the excitation of a single albeit broad surface plasmon (SP) band of the gold nanocube. The extinction cross section of the gold nanocube is dominated by the absorption cross section that gains importance as the width increases. Further increasing the nanocube size beyond 80 nm will result in an optical response mainly characterized by scattering properties. The absorption spectrum of the nanobar shows the excitation of both the longitudinal mode (LM) and the transverse mode (TM). The nanobar is also compared to a cylinder, a spherically capped cylinder, and a spheroid of the same aspect ratio. The band position of the TM of the nanobar is red-shifted as compared to the ones calculated for other morphologies, while the LM is either blue-shifted or red-shifted depending on the morphologies considered.

Comparison between discrete dipole approximation and other modelling methods for the plasmonic response of gold nanospheres

2013 ◽  
Vol 115 (2) ◽  
pp. 237-246 ◽  
Author(s):  
V. L. Y. Loke ◽  
G. M. Huda ◽  
E. U. Donev ◽  
V. Schmidt ◽  
J. T. Hastings ◽  
...  
Keyword(s):  
Dipole Approximation ◽  
Discrete Dipole Approximation ◽  
Gold Nanospheres ◽  
Modelling Methods
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