جستجوی مقالات مرتبط با کلیدواژه "plasmon" در نشریات گروه "فیزیک"

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.

The laser back writing process (LBW) on the glass and quartz has been studied in the present work. For this purpose, a steel target was irradiated with Q-switched Nd:YAG laser pulses. As a consequence of the laser irradiation, the produced plasma is penetrated onto the glass and quartz substrates. The process was compared for two different samples. The effects of the pulse numbers and the laser fluence on the morphology and the target material penetration on the substrate were investigated. The results show that this process produces microchannels with the controlled dimensions (the depth and width) on the substrate. The presence of the nanoparticles (Fe and Cr ions on quartz and Fe ions on glass) is an important result of this process that can affect the microchannels' function. Irradiation parameters, including the number of pulses, the laser fluence, the pulse repetition rate, and the substrate material, affect the channel quality and the type and rate of the ion penetrated onto the substrates. The width of the channels for the quartz sample is greater than that of the glass sample, and also, more ions are deposited on the quartz substrate than the glass. The EDX and UV-Visible spectroscopies were used for studying the penetration rate and the type of ions present on the substrates. The surface profilometer and scanning electron microscopy were used to investigate the profile and the width of the affected area. X-ray fluorescence spectroscopy (XRF) was used to study the metal target's composition.

In this article using a modified Drude model, which includes all dominant electron energy scattering mechanisms and interparticle interactions, the relativistic dynamics of a linear chain of spherical nanoparticle interacting with a laser beam propagating parallel to the orientation of nanoparticles array is investigated. In the point-dipole description of nanoparticles, taking into account interaction of two nearest neighbors, analytical solutions are obtained for the momentum equations of conducting electrons of nanoparticles related to the first, second and third harmonics of laser fields. Formulae are simplified for some asymptotic cases. Numerical analysis is carried out for a linear chain including 10 of 10nm radius Au nanoparticles. It is shown that the interparticle separation has a key role in the nonlinear dynamics of the system. Dipole-dipole interaction of nanoparticles causes a blueshift for the main and third harmonics plasmon resonance, whereas it leads to a redshift for the plasmon resonance of the second order longitudinal displacements of nanoparticles. Related to the different orders, linear and nonlinear polarization of each particle is obtained and permittivity, first and second order susceptibility, linear and nonlinear refractive index of each nanoparticle are analytically obtained which these findings can have direct application in nano-optics and nano-plasmonics.

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.

Plasmonic properties of metals such as gold is the main factor in the development of optical fiber sensors. Plasmonic property is created by exciting the surface plasmon polaritons by laser radiation. These properties are usually used in boosting and detection. The article examines and compares the collected information such as the length of the fiber optical sensor and the sensitivity of sensors including wave guides, fiber brag gratings and Wagon Wheel optical fiber in recent years.

An investigation isundertaken to study the transmission of the electromagnetic waves through inhomogeneous over-dense plasma. The transmission is due to the excitation of the surface modes of plasma or plasmons. The construction of the plasma is in such a way that the charge density of the plasma linearly increases and passes through its critical value and then linearly decreases. The dissipative effects are considered for the plasma. The amplitude of the electromagnetic waves and the reflection coefficient are calculated and then the distribution of the electric field amplitude of the entire structure is obtained and discussed. In this way، itis shown that the considered structure facilitates the anomalous wave transmission through over-dense plasma medium.