Value Of Plasma Frequency Research Articles

Deflection angle analysis under the influence of non-plasma medium and plasma medium for regular black hole with cosmic string

By applying the Keeton and Petters technique, we find the deflection angle as a series expansion with a specific factor of mass. We investigate the shadow structure of a regular black hole with cosmic string with a non-magnetized, pressure-free plasma around it. In order to separate the Hamilton equation and locate the photon areas, certain plasma distributions are taken into consideration. Moreover, by utilizing a new ray-tracing technique, we analyze the photon’s path around a regular black hole with cosmic string in the presence of plasma whose density depends on the radius coordinate. We also analyze the plasma effects on the shadow of black hole. We obtain an analytical formula that describes the boundary curve of the shadow for such a black hole in an expanding universe for an observer at any finite location outside the horizon. In the presence and absence of plasma, we detect deviations that are further investigated by analyzing the geometry of shadow angle at a particular value of plasma frequency.

Computational Analysis of Weakly Magnetized Plasma's Effects on Electromagnetic Wave Propagating Perpendicular to the Magnetic Field

Magnetised plasma influences electromagnetic wave propagation, this resulting in polarisations at different velocities, an effect that can result in ghost signals. This work provided critical information on the effects of magnetized plasma on electromagnetic (EM) wave propagation perpendicular to the magnetic field. Electromagnetic waves propagating perpendicular to the magnetic field in a weakly magnetized plasma were studied. Furthermore, there are two modes of EM wave propagation perpendicular to the field: ordinary (O) and extraordinary (X). The values of the ordinary (O) mode's frequency were obtained by substituting the values of its wave number (k) into its dispersion relation, while the same frequency values were substituted to obtain the values of its refractive index (η_O^2). The plasma frequency values derived from the Bohm-Gross formulae for electron plasma. The plasma frequency values obtained from the Bohm-Gross formulae for electron plasma waves were substituted into the extraordinary mode dispersion relation to obtain frequency values with cut-off frequencies at ω_L and ω_R. The refractive index values were calculated using the same frequency values (X-mode). The results revealed that for EM wave propagation perpendicular to magnetic field in a weakly magnetized plasma in vacuum, the speed as well as the direction was unperturbed. The results also revealed that the properties of electromagnetic waves propagating perpendicular to magnetic field in a weakly magnetized plasma in an ordinary (O) mode were different from those for extraordinary (X) mode, with the former having a higher phase speed than the latter. Additionally, we discovered that, the phase velocity (υP) exceeded the speed of light (c), which is consistent with the basic ideas of special relativity.

Hybrid surface plasmon polariton (SPPs) modes between metal and anisotropic plasma interface

This manuscript investigates the properties of surface plasmon polaritons (SPPs) at anisotropic plasma metal interface. It has been shown that magnetized plasma surface plasmon waves have unique features such as hybridization nature, the existence of cutoff frequency and the dependence of normalized prorogation constant and prorogation length on plasma parameters such as cyclotron frequencies (𝜔𝑐) and plasma frequency (𝜔𝑝). The influence of plasma features on normalized propagation constant and propagation as the function of frequency under different values of plasma frequency and cyclotron frequencies are studied. This suggest SPPs at magnetized plasma metal interface may be exploited for Plasma-on-Chip for cancer treatment.

Dynamic control over group speed of light in plasma cladded optical fiber: An analytical approach

The ability of plasma frequency to tune the guiding properties of plasma cladded optical fiber is explored and numerically investigated. The identified parameter to manipulate the propagation characteristics of the investigated structure is electron–ion density which can be controlled by varying electric potential. It is shown that the curve of group index vs optical signal frequency can be manipulated significantly by manipulating plasma frequency. Judicious consideration of fiber’s parameters and the values of plasma frequency allow for obtaining minimum or desired group velocity dispersion at a desired optical frequency. Further, ability of manipulation of the slope of group index vs signal frequency curve allows for dispersion management. Possibility of significant variation in group-index is the highlight of the present work and the most impressive feature is that it could be achieved in online condition (by varying plasma frequency with the help of tuning electric field). Since, ratio of plasma to signal frequency is the only important factor in manipulating the propagation properties, the idea presented here can be extended to frequency domains in the range of Terahertz, Microwaves etc. An optical modulator is proposed in the last section on the basis of present investigation.

Plasma frequency demand for mode conversion processes from slow Z-mode to LO-mode waves in an inhomogeneous plasma

The mode conversion process responsible for radio wave generation has been studied for several decades; however, the properties of the condition required for an efficient conversion process are still unknown. The aim of this study is to determine the value of plasma frequency required for an efficient mode conversion process from slow Z-mode to left-hand ordinary (LO)-mode waves in the matching cases, where the two branches of the dispersion relation of the two modes are perfectly connected. We derive the dispersion relations for electromagnetic wave propagation in an inhomogeneous plasma considering Snell’s law and investigated them in detail. We quantify the minimum variation of plasma frequency required for the efficient mode conversion process, which we call “the plasma frequency demand.” We show that the condition required for the efficient mode conversion can be satisfied by waves propagating first toward the high-density region and then returning toward the low-density region before reaching the region where the wave frequency matches the cutoff frequency; therefore, a large inhomogeneity is not always required. We show that the angle between the background magnetic field and the density gradient has a significant effect on the plasma frequency demand.

OPTICAL MODELING OF FLUORINE DOPED TIN OXIDE FILMS FOR SPECTRALLY SELECTIVE APPLICATIONS

SnO2: F films are widely used for solar cell applications as the front electrode as well as other applications such as electrochromic and displays. The optical design of these and other applications need knowledge of optical constants. In this study we used the dielectric constant of a combined Drude and Lorentz to model the optical behaviour of SnO2: F. To do this, we used the fitting parameters from existing literature. From the model we got n and k values which we inserted into Fresnel R and T calculator and computed R and T spectra over the 300nm -2500nm wavelength range using Fresnel’s equations. We plotted n, k, T and R for different values of plasma frequency, and damping parameter, . The films exhibited very high visual transmittance and high infrared reflectance. The results implied the possibleness of the films to be employed as spectrally selective coating materials.

Effect of linear absorption on self focusing of Hermite Gaussian laser beam in plasma in relativistic and ponderomotive regime

Effect of linear absorption, intensity of fundamental laser pulse and plasma frequency on beam width parameter is investigated to study the self-focusing of Hermite-Gaussian(HG) laser beam in plasma under relativistic and ponderomotive regime. Intense short pulse laser propagates through plasma imparts oscillatory velocity to electrons and non linearity arises. Using the paraxial approach we have derived the second order differential equation for beam width parameter and the equation for normalized radius of incident beam is also obtained using the critical condition. The outcome of our study reveals that light absorption and intensity of radiation enhance the self focusing of Hermite-Gaussiam laser beam. It is observed that the beam width parameter shows significant decrease for higher values of linear absorption coefficient and plasma frequency. We also observe that radius of the incident beam decreases sharply with increasing intensity of incident pulse for higher values of plasma frequency.

A first principles study of high Bi content in GaSbBi supercell structures for optoelectronic applications

We report the study of structural and optical properties of high Bi content in GaSb supercell leading to the formation of 2х2х1 and 1х2х2 GaSb0.875Bi0.125 supercell structures. This calculation has been performed using the density functional theory (DFT) formalism of Full Potential Linear Augmented Plane Wave (FP-LAPW) method employing WIEN2K package. The minimum volume, bulk modulus, differential pressure and the total energy for both the structures have been investigated under equilibrium conditions. Calculation of optical properties includes absorption, reflection, refraction, extinction co-efficient and the energy losses in both the supercell structures. Phenomenally both the structures are highly stable although the 2х2х1 supercell has a higher compressive flexibility as well as higher total minimum energy in comparison to the 1х2х2 supercell structure. Moreover, the calculated lattice parameters indicate both the structures to be of Zinc Blende in nature. The refractive index and the extinction coefficient values are observed to be higher for 2х2х1 than 1х2х2 supercell structure in the considered incident photon energy range. Significantly, the characteristic curve of refractive index and extinction co-efficient are retraced by the real and imaginary part of the dielectric for both the structures. The optical band gap and maximum optical conductivity has been found to be higher for the 1х2х2 supercell structure in comparison to its counterpart. The reflection and the energy loss characteristic curve are found to be contradictory to one another. The reflectivity coefficient maintains almost a constant value along the incident photon energy range for both the structures; although, the 2х2х1 supercell structure obtains a higher value than the 1х2х2 supercell structure and the vice-versa phenomenon is observed for the energy loss characteristic curve. At higher values of incident photon energy, both the structures attains its distinct plasma frequency values.

Study of the Structural, Electronic, Magnetic, and Optical Properties of Mn2ZrGa Full-Heusler Alloy: First-Principles Calculations

In this work, the structural, electronic, magnetic, and optical properties of Mn2ZrGa full-Heusler alloy were investigated by using density functional theory (DFT) calculations. It is found that the spin-up states have a metallic character, but the spin-down bands have a pseudo-gap at the Fermi level. The total spin magnetic moment of Mn2ZrGa (per formula unit) is 3.00 µ B at an equilibrium lattice parameter of 6.15 A. The calculations show that Mn2ZrGa is a ferrimagnetic with 81% spin polarization at equilibrium lattice parameter. The effect of lattice parameter distortion on the magnetic properties and spin polarization is also studied. It is found that the total magnetic moment preserves its value for a lattice parameter range of 5.96–6.30 A. The decreasing of the lattice parameter leads to improvement of spin polarization. The real and imaginary parts of dielectric function and hence the optical properties including energy absorption spectrum, reflectivity, and optical conductivity are also calculated. The value of plasma frequency for spin-up and down electrons is located at 1.78 and 0.74 eV, respectively.

Plasma effects on the free-electron laser gain with a plasma wave undulator

Employing a magnetized plasma medium in the interaction region of a free-electron laser (FEL) offers the possibility of generating short wavelengths using moderate energy beams. Plasma in the presence of static magnetic field supports right and left circularly polarized electromagnetic modes. By superposition of these two modes, a linearly polarized electromagnetic mode is generated which can be employed as a plasma undulator in a FEL. This configuration has a higher tunability by controlling the plasma density on top of the -tubability of the conventional FELs. The roles of the axial magnetic field and plasma on the laser gain and the electron trajectories of an e-beam propagating through the plasma medium have been studied and new orbits of group (I, II, and III) have been found. Moreover, the stability of these orbits for different values of plasma frequencies has been investigated. It is shown that by increasing the axial guide magnetic field strength, the gain for orbits of group I trivially increase, while a decrease in gain has been obtained for orbits of group II and group III. In addition, it is found that with increasing the plasma frequency (or plasma density) the gain for orbits of group I and group II trivially decreases and shift to the lower cyclotron frequencies, while an increase in gain has been obtained for orbits of group III.

Investigation of the annealing effects on the structural and optoelectronic properties of RF-sputtered ZnO films studied by the Drude–Lorentz model

Zinc oxide films were deposited on glass substrates by RF reactive magnetron sputtering and post-annealed in vacuum at 100, 200, and 300 oC. Structural and optical properties of films were obtained using X-ray diffraction and UV–visible spectroscopy. Optical parameters were extracted from transmittance curves using the single-oscillator Drude–Lorentz model. The evolution of the optical and structural properties of films with the annealing process was investigated. The films crystallized into the hexagonal wurzite lattice structure, with preferential growth along the c-axis [0002]. The results indicate that the crystalline quality of films improved with annealing, whereas transparency was reduced from 90 to 80 % at 300 oC. With post-annealing, the absorption edge shifted to the red, while the optical band gap decreased from \({E}_{{\text {g}}}=3.28\) to \({E}_{{\text {g}}}=3.26\) eV because of the Burstein–Moss effect. Calculated values of plasma frequency, \(w_{{\text {p}}},\) fall within the IR range and decrease with temperature, from \(w_{{\text {p}}} =5.56 \times 10^{14}\) rad/s (\(2950\,{\text {cm}}^{-1}\)) to \(w_{{\text {p}}}=1.1 \times 10^{14}\) rad/s (\(587\,{\text{cm}}^{-1}\)).

Радиопрозрачность ионизованной оболочки, образующейся вокруг гиперзвукового объекта в мезосфере

This article discusses the basic properties of ionized gas shell formed around objects moving in the mesosphere at hypersonic speeds to determine the frequency band for the radio communication. Ionization occurs due to the energy of the shock wave. The thickness of the transition layer is defined between molecular distances. Limiting compression due to the Hugonio adiabat and depends on the number of degrees of freedom – for diatomic gas is equal to 6. The energy which remained when braking goes for heating of gas in a shock wave and, agrees Sakha, to ionization. Temperature field of the shell taking into account the heat transfer coefficient is much higher surface temperature of the object. Near the bow, which overheating, for example, Buran reaches 1400 °C, the gas temperature exceeds 10 000 °С – this is at a height 63 km and at a speed of 17 Machs. The shell is three-component gas. There are atoms (molecules), ions and electrons with a low degree of ionization. The main features are the frequency of collisions of electrons with atoms and the plasma frequency. If the plasma frequency exceeds the frequency of collisions, the medium is a gas plasma. If the frequency of collisions exceeds value of plasma frequency, gas doesn't reach a plasma status. The plasma frequency is critical: above the critical frequency gas plasma is dominated by the dielectric properties, and to the critical frequency – dominated conductive properties. Plasma sheath radio transparency if the value of the skin layer to the body exceeds the normal thickness of the shell. Calculations and model tests show that the transparency of the radio channel is provided in the centimeter range, where f > 9 GHz.

Sulvanite Compounds Cu<sub>3</sub>TMS<sub>4</sub> (TM = V, Nb and Ta): Elastic, Electronic, Optical and Thermal Properties using First-principles Method

We present a systematic first-principles study of the structural, elastic, electronic, optical and thermodynamics properties of the sulvanite compounds Cu3TMS4 (TM = V, Nb and Ta). The structural, elastic and electronic properties are in fact revisited using a different calculation code than that used by other workers and the results are compared. The band gaps are found to be 1.041, 1.667 and 1.815 eV for Cu3VS4, Cu3NbS4 and Cu3TaS4, respectively which are comparable to other available calculated results. The optical properties such as dielectric function, refractive index, photoconductivity, absorption coefficients, reflectivity and loss function have been calculated for the first time. The calculated results are compared with the limited measured data on energy dependent refractive index and reflectivity coefficient available only for Cu3TaS4. All the materials are dielectric, transparent in the visible range. The values of plasma frequencies are found to be 15.36, 15.58 and 15.64 eV for Cu3VS4, Cu3NbS4 and Cu3TaS4, respectively. Furthermore, following the quasi-harmonic Debye model, the temperature effect on the bulk modulus, heat capacity, and Debye temperature is calculated reflecting the anharmonic phonon effects and these are compared with both experimental and other theoretical data where available. © 2014 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved.doi: http://dx.doi.org/10.3329/jsr.v6i3.19191 J. Sci. Res. 6 (3), 407-419 (2014)

Millimeter Wave Propagation through Plasma

Theoretical investigation has been carried out to evaluate the attenuation constant and phase velocity of millimetre wave in plasma. For this purpose the expression for the permittivity of plasma medium is obtained. The concept of Faraday rotation has been introduced for utilisation of the same for further calculation. It has been found that attenuation constant and phase velocity both increase with increasing value of plasma frequency. However, the value of attenuation constant decreases with increasing operational frequency.Key words: Plasma; Millimetre wave; Faraday Effect; Attenutation constant; Phase velocityThe Himalayan Physics Vol.1, No.1, May, 2010Page: 34-36Uploaded Date: 28 July, 2011

Parameterized Regional Ionospheric Model and a comparison of its results with experimental data and IRI representations

We describe a Parameterized Regional Ionospheric Model (PARIM) to calculate the spatial and temporal variations of the ionospheric electron density/plasma frequency over the Brazilian sector. The ionospheric plasma frequency values as calculated from an enhanced Sheffield University Plasmasphere–Ionosphere Model (SUPIM) were used to construct the model. PARIM is a time-independent 3D regional model (altitude, longitude/local time, latitude) used to reproduce SUPIM plasma frequencies for geomagnetic quiet condition, for any day of the year and for low to moderately high solar activity. The procedure to obtain the modeled representation uses finite Fourier series so that all plasma frequency dependencies can be represented by Fourier coefficients. PARIM presents very good results, except for the F region peak height (hmF2) near the geomagnetic equator during times of occurrence of the F 3 layer. The plasma frequency calculated by IRI from E region to bottomside of the F region present latitudinal discontinuities during morning and evening times for both solar minimum and solar maximum conditions. Both the results of PARIM and the IRI for the E region peak density show excellent agreement with the observational values obtained during the conjugate point equatorial experiment (COPEX) campaign. The IRI representations significantly underestimate the foF2 and hmF2 compared to the observational results over the COPEX sites, mainly during the evening–nighttime period.

Optical modeling of free electron behavior in highly doped ZnO films

Transparent conductive oxides (TCOs) with tailor-made electrical and optical properties are essential for a variety of applications. The linkage of optical and electrical properties in these films is usually described by the Drude theory despite the fact, that earlier investigations have already shown that the Drude theory fails to accurately describe optical properties. In this work we use an extension to the Drude theory to model optical spectra of reactively sputtered ZnO:Al thin films. The model uses a simple analytic expression, which can describe the general course of the dielectric function as calculated by others with more elaborate models. Using this approach optical spectra can be accurately modeled with low computational effort and reliable values for plasma frequency and damping can be obtained. By comparing these results with Hall measurements we derived the effective mass of free carriers m ⁎ in the conduction band as a function of carrier concentration. The results clearly showed the non-parabolicity of the conduction band for high doping levels. Using the band structure proposed by Pisarkiewicz and assuming an effective mass of 0.24 electron masses at the conduction band minimum we derived a non-parabolicity parameter of ~ 0.27 (2) eV − 1 . Finally we used the values for the effective mass to determine carrier mobility from optical measurements. Contradictions to Hall measurements can be explained by the effect of grain boundary scattering.

Phase matching for third-harmonic generation in collisional magnetoplasmas

This paper presents a derivation of the phase-matching conditions for generation of the third-harmonic (3ω1) and combination frequencies (ω1+2ω2), by two fundamental electromagnetic waves of frequencies ω1 and ω2, propagating in the extraordinary mode along a magnetic field in a collisional plasma. Expressions for the corresponding optimum distance of propagation for maximum output and the associated values of the phase functions have been derived. In the case of the third-harmonic generation phase matching occurs when the gyrofrequency of the electrons is twice the wave frequency (for all values of plasma frequency). In the case of the combination frequencies, the phase-matching condition is represented by an expression for plasma frequency ωp in terms of the wave frequencies ω1, ω2 and the gyrofrequency ωc of electrons. Furthermore, it is seen that in the (ωc∕ω1)−(ω2∕ω1) plane, phase matching occurs in a narrow region; for every point in this region, there is a corresponding value of (ωp∕ω1). The dependence of optimum distance of propagation and the corresponding value of the phase function on electron collision frequency νav∕ω1 have been graphically illustrated for a specific case. An estimate of the maximum value of the third-harmonic conversion efficiency has also been made.

First observation of quasi-2-day oscillations in ionospheric plasma frequency at fixed heights

Abstract. The existence and development of the quasi-2-day oscillations in the plasma frequency variations of the F region at northern middle latitudes are investigated. A new approach to study the quasi-2-day oscillations is presented, using a methodology that allows us to do such a study at fixed heights. The hourly values of plasma frequency at fixed heights, from 170 km to 220 km at 10 km step, obtained at the Observatori de l'Ebre station (40.8°N, 0.5°E) during 1995 are used for analysis. It is found that quasi-2-day oscillations exist and persisted in the ionospheric plasma frequency variations over the entire year 1995 for all altitudes investigated. The dominant period of oscillation ranges from 42 to 56 h. The amplitude of oscillation is from 0.1 MHz to 1 MHz. The activity of the quasi-2-day oscillation is better expressed during the summer half year when several enhancements, about 15–30 days in duration, were observed. The largest enhancements of the oscillation occurred during early June, July and early August; i. e., near and after the summer solstice when the 2-day wave in the middle neutral atmosphere typically displays its largest activity in the Northern Hemisphere. The results obtained may help us understand better the possible influencing mechanisms between the 2-day wave in the middle neutral atmosphere and the ionospheric quasi-2-day oscillations.Key words. Ionosphere (Ionosphere - atmosphere interactions; Mid-latitude ionosphere; Plasma waves and instabilities)

First observation of quasi-2-day oscillations in ionospheric plasma frequency at fixed heights

The existence and development of the quasi-2-day oscillations in the plasma frequency variations of the F region at northern middle latitudes are investigated. A new approach to study the quasi-2-day oscillations is presented, using a methodology that allows us to do such a study at fixed heights. The hourly values of plasma frequency at fixed heights, from 170 km to 220 km at 10 km step, obtained at the Observatori de l'Ebre station (40.8°N, 0.5°E) during 1995 are used for analysis. It is found that quasi-2-day oscillations exist and persisted in the ionospheric plasma frequency variations over the entire year 1995 for all altitudes investigated. The dominant period of oscillation ranges from 42 to 56 h. The amplitude of oscillation is from 0.1 MHz to 1 MHz. The activity of the quasi-2-day oscillation is better expressed during the summer half year when several enhancements, about 15–30 days in duration, were observed. The largest enhancements of the oscillation occurred during early June, July and early August; i. e., near and after the summer solstice when the 2-day wave in the middle neutral atmosphere typically displays its largest activity in the Northern Hemisphere. The results obtained may help us understand better the possible influencing mechanisms between the 2-day wave in the middle neutral atmosphere and the ionospheric quasi-2-day oscillations.Key words. Ionosphere (Ionosphere - atmosphere interactions; Mid-latitude ionosphere; Plasma waves and instabilities)

Burstein-Moss shift in CulnSe 2 films

Optical properties of copper-indium-diselenide films were studied in the wavelength range of 500–3000 nm. The data were analysed in the light of the existing theories and indicated a Burstein-Moss shift in these films. The dependences of refractive index and extinction coefficient were studied as a function of photon energy and the values of plasma frequency and dielectric constants were generated from the above. Correlation of the above data indicated an effective mass Mp ∗ = 0.72 Mo , Mo being the free electron mass.