In this article, the optical properties of Graphene/Au nanocubes have been studied for the different number of graphene layers on 1 or 2 faces of cubes. The extinction efficiency factor has been calculated in the near and far-field regime by the discrete dipole approximation (DDA) method. Our results show that the height of extinction's peak decreases significantly, by increases number of graphene layers on nanocube. Moreover, the wavelength of surface plasmon resonance peak redshifts from 516 to 700 nm (this peak is due to dipole formed alonge the polarisation direction), although the wavelength of the another peak stays constant about 230 nm(this peak is due to dipole formed perpendicular to the polarisation). In addition, with increasing size of nanocubes, the height of peaks decrease, the width of them increase and wavelength of plasmon peaks don't show any shifts for a constant thickness of graphene. The results of this study may be used for fabrication of biological sensors at vis wavelength.

In this paper, we investigate optical properties of silver ellipsoid nanostructures (SENs) by means of discrete dipole approximation (DDA), when these nanoparticles are embedded into the water. Absorption, scattering and extinction cross-sections of the SENs were calculated by change of incident wavelength in visible and near infrared region. Moreover, height, wavelength and full width at half maximum (FWHM) of extinction cross-section peaks (due to plasmon resonances) were studied by change of nanostructure's size and dielectric constant of medium. Our results show that, there are only two peaks of transverse dipole and longitudinal dipole modes in this spectrum.

In this paper, we investigate optical properties of silver pyramid nanostructures (SPNs) by means of discrete dipole approximation (DDA), when these nanoparticles are embedded into the water. Absorption, scattering and extinction cross-sections of the SPNs were calculated by change of incident wavelength in visible and near infra-red region. Moreover, height, wavelength and full width at half maximum (FWHM) of extinction cross-section peaks (due to plasmon resonances) were studied by change of nanostructure's size and dielectric constant of medium. Our results show that, there are only two peaks of dipole and quadruple modes in this spectrum.

In this paper, the interaction between an oscillating dipole moment and a Silver nanoparticle has been studied. Our calculations are based on Mie scattering theory and discrete dipole approximation (DDA) method. At first, the resonance frequency due to excitingthe localized surface plasmons has been obtained using Mie scattering theory and then by exciting a dipole moment in theclose proximity of the nanoparticle, the induced charge distribution on the nanoparticle surface has been calculated. In our calculations, we have exploited the experimental data obtained by Johnson and Christy for dielectric function.

In this work, the extinction spectra of the nano-structure of the Tilt Helical and Stair-like Towers of Mn thin films were obtained using discrete dipole approximation (DDA) simulation for both s-and p-polarization at two incident light angles of 10° , and 60° at different azimuthal angles for the there samples with different tilt. Obtained results are compared with the experimental optical extinction spectra. The plasmonic peaks appeared at wavelength about 600 nm for both experimental measurments and theory calculations. The experimental spectra for some of the samples are changed in some of the azimuthal angles which are called spectral abnormal. These abnormals is due to the change of the tilt angle and increasing the shadowing effect in the structure of the film, which this may cause increasing the surface fraction of void and forming defects in the structure. However, in the simulation results are not observed these obnormals beacause the voids and defects in the structure becomes negligible and this is the most difference important in spectra obtained for both the experimental and theory results.

By making a modification to the usual discrete dipole approximation (DDA) method, the effect of different molecules on the plasmonic properties of silver nanoparticles was investigated. Several calculations were performed for molecules with different structures, sizes and concentrations. The obtained results indicated that considering that the modified DDA method is very sensitive to the geometrical details and the type of atoms of the guest molecule, the smallest change in the dimensions and also the type of atoms of the guest molecule leads to a change in the peak wavelength of the absorption spectrum of silver nanoparticle. These changes are unique for different molecules with good accuracy.

In this work, the discrete dipole approximations (DDA) theorywas used to investigate the absorption spectrum of annealed Zn nano rods in oxygen flux. For this purpose, the Zn nanorod was replaced with 1786 dipoles arranged on a rod-shaped structure, and the interaction of these dipoles with polarized light was investigated. In this study, it was found that the extinction spectrum has two absorption peaks, which are related to the plasmonic oscillations, and Zn nanorods annealed in oxygen flux show metallic behavior. Changes in plasmonic oscillations were investigated by changing the deposition angle of nanorods and it was found that the oscillations in the direction perpendicular to the axis of the nanorod are strongly dependent on the angle of deposition and with increasing deposition angle, the number of oscillating dipoles and consequently the intensity of the absorption decreases sharply.

The use of glancing angle deposition technique provides opportunities for the deposition of sculptured nanostructures of different shape. The optical properties of such nanostructures that are a function of the shape of these nanostructures may be investigated, using the discrete dipole approximation theory which is an appropriate method for solving the light scattering problem from objects of different shape and geometry. In this paper, the extinction spectra of Ag/glass-sculptured nano-flowers with threefold symmetry are modeled and calculated, while the results are compared with similar experimental observations. In modeling the nano-flower-shaped sculptured thin films, it is proposed that the nano-flower is formed as a combination of two chiral thin films with different dimensions. This structure was replaced with 1, 405 electrical dipoles, and its extinction spectrum was calculated as a function of incident light angle and azimuthal angle. The extinction spectrum consists of both transverse and longitudinal modes of oscillations. The results showed that by increasing the incident angle, due to increase of amplitude of electrical oscillations, transverse oscillations shift towards longer wavelengths. It was also observed that at azimuthal angles close to nano-flower petals, where sharp points or recesses may exist, the intensity of extinction spectrum for longitudinal mode (long wavelengths in the extinction spectrum) increases.

Extinction spectra of chiral silver nanostructures are calculated by means of Discrete Dipole Approximation (DDA).Dependence of Plasmonic peaks to both structural parameters of nanostructures and direction of the incident light are obtained. This dependence is investigated on variation of chiral dimensions, chiral shape and direction of incident light. We have observed a resonance peak of transverse mode (TM) for the extinction spectra of chiral structure at normal incidence. However, for oblique angle incident light, in addition to the TM mode, a longitudinal mode (LM) appears at longer wavelengths. The latter undergoes a shift to longer wavelengths with increasing the diameter of chirl arm. When the cross-section of chiral is changed to an oval this resonance peak disappears, while some other peaks appear at longer wavelengths that were not present for a chiral with circular cross-section.Extinction spectra of chiral nanostructure with different structural parameters and different rise angles (slanted chirals) showed dependence on the incident light direction.

The aim of this paper is to introduce the notion of discrete and inverse discrete weighted transform. We show that discrete input data can be converted to a continuous approximation through the inverse discrete weighted transform.