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Nanoplasma properties in metallic clusters driven by a Gaussian laser beam in the presence of helical magnetic undulator
摘要： The motivation of present paper is the investigation of effective permittivity and absorption cross section of cluster nanoplasmas in the interaction of a Gaussian laser beam with a cluster of metallic nanoparticles, in the presence of a helical magnetic undulator. The static magnetic field of the undulator couples with the field of the laser wave, and forms a nonlinear force in the interaction region. As a result, the nonlinear force varies the plasmonic oscillations of the electron of nanoplasmas that leads to electron density modulation, which modifies absorption cross section and effective permittivity of nanoparticles. Using a perturbative method, we analytically derived the nonlinear dispersion waves and dielectric constant of metallic nanoparticles lattice (gold, silver, and copper) in the presence of a helical magnetic undulator. Numerical results indicate that with increasing the undulator magnetic field strength, absorption cross section of cluster nanoplasmas increases and absorption phenomenon occurs at frequencies close to the effective plasma frequency. Besides, with decreasing distance of nanoparticles in the cluster (and with increasing the nanoparticles radius), absorption cross section increases. We also found that the dielectric constant of the cluster nanoplasma medium increases with enhancing undulator magnetic field strength only near the effective plasmonic frequency. This concept opens a path toward new properties of cluster nanoplasmas as quantum dots, diagnostics, and sensors based on magnetic undulator structures.
关键词： Gaussian laser beam,Effective permittivity,Metallic clusters,Nanoplasma,Absorption cross section,Helical magnetic undulator
更新于2025-09-19 17:13:59
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Characterization of core–shell nanostructure consisting Si–Au–SiO2 based on manipulation of optical properties
摘要： In this article, we investigated some physical characteristics of core–shell nanostructure in optical regime and perturbation has been also introduced as an effective method in shaping of optical properties. The proposed nanostructures are composed of the selected materials as: Silicon, Silicon Dioxide and Gold. At first, the extinction cross section spectra are calculated for multilayer core–shell nanostructures in optical range and the configuration effect of the constructed materials in a multilayer nanostructure are investigated for determination of Plasmon range. Then, the new structures of core–shell nanoparticles (gold–silicon) are presented, which have an amount of impurity particle in their shells as perturbation and also their extinction cross section spectra are calculated. The obtained results in this article give a proper approach about perturbation effect in broadening, sharpening and shifting of optical response which are decisive factors especially nano-network systems. Indeed, it has been proposed that the impurity particles in the shells can be a mechanism for tuning of optical characteristics of the presented nanoparticles in practical fields and also creation of local oscillations as plasmonic resonances in a considered optical range. Besides, redshift in extinction cross section can be also created by particle perturbation. At the end, the effective permittivity of the perturbed core-shells are extracted. The optional frequency range is selected between 300 and 900 (THz).
关键词： Effective permittivity,Perturbation,Nanoparticle impurity,Extinction cross section,Core–shell nanostructure,Plasmonic resonance frequency
更新于2025-09-09 09:28:46
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A NOVEL DNG MEDIUM FORMED BY FERROMAGNETIC MICROWIRE GRID
摘要： Effective permittivity and permeability of a medium consisting of an infinite number of ferromagnetic microwires are evaluated in this paper. Analysis is carried out with the help of local and average fields inside a unit cell. In the literature, effective permittivity of the microwire grid is obtained by assuming the grid as an impedance loaded surface. The analysis is applicable only for the case of T Mz polarized normally incident wave. Proposed analysis enable us to evaluate all the three diagonal components of effective permittivity and permeability for arbitrarily incident uniform plane wave having arbitrary polarization angle. Numerical results are obtained through MATLAB, and a comparison is done with the results available in the literature for validation. Numerical results have shown a DNG like behaviour of the medium for a T Mz polarized incident wave.
关键词： effective permittivity,ferromagnetic microwires,T Mz polarization,DNG medium,arbitrary polarization,effective permeability,T Ez polarization
更新于2025-09-04 15:30:14