Effect of spin on the instability of THz plasma waves in field-effect transistors under non-ideal boundary conditions

Terahertz(THz) radiation can be generated due to the instability of THz plasma waves in field-effect transistors(FETs). In this work, we discuss the instability of THz plasma waves in the channel of FETs with spin and quantum effects under non-ideal boundary conditions. We obtain a linear dispersion relation by using the hydrodynamic equation, Maxwell equation and spin equation. The influence of source capacitance, drain capacitance, spin effects, quantum effects and channel width on the instability of THz plasma waves under the non-ideal boundary conditions is investigated in great detail. The results of numerical simulation show that the THz plasma wave is unstable when the drain capacitance is smaller than the source capacitance;the oscillation frequency with asymmetric boundary conditions is smaller than that under non-ideal boundary conditions;the instability gain of THz plasma waves becomes lower under non-ideal boundary conditions. This finding provides a new idea for finding efficient THz radiation sources and opens up a new mechanism for the development of THz technology.

Propagation properties of the chirped Airy–Gaussian vortex electron plasma wave

We introduce a new class of the chirped Airy–Gaussian vortex electron plasma(CAiGVEP)wave which constitutes the exact and continuous transition modes between the chirped Airy vortex and the chirped Gaussian vortex electron plasma wave.The intensity,the phase,and the angular momentum density flow of the CAiGVEP wave are discussed under different distribution factors and different chirp modes.

Terahertz Plasma Waves in Two Dimensional Quantum Electron Gas with Electron Scattering

We investigate the Terahertz （THz） plasma waves in a two-dimensional （2D） electron gas in a nanometer field effect transistor （FET） with quantum effects, the electron scattering, the thermal motion of electrons and electron exchange-correlation. We find that, while the elec- tron scattering, the wave number along y direction and the electron exchange-correlation suppress the radiation power, but the thermal motion of electrons and the quantum effects can amplify the radiation power. The radiation frequency decreases with electron exchange-correlation con- tributions, but increases with quantum effects, motion of electrons. It is worth mentioning that radiation frequency. These properties could be plasma oscillations in nanometer FET. the wave number along y direction and thermal the electron scattering has scarce influence on the of great help to the realization of practical THz

THz plasma wave instability in field effect transistor with electron diffusion current density

The plasma wave instability in rectangle field effect transistors （FETs） is studied with electron diffusion current density by quantum hydrodynamic model in this paper. General dispersion relation including effects of electrical thermal motion, external friction associated with electron scattering effect, electron exchange-correlation contributions and quantum effects were obtained for rectangle FETs. The electron diffusion current density term is considered for further analysis in this paper. It is found that the quantum effects, the electron diffusion current density and electrical thermal motion enhance the radiation power and frequencies. But the electron exchange- correlation effects and the electron scattering effects reduce the radiation power and frequencies. Results showed that a transistor has advantages for the realization of practical terahertz sources.

Relativistic Spherical Plasma Waves in a Collisional and Warm Plasma

Under Lagrange coordinates, the relativistic spherical plasma wave in a collisional and warm plasma is discussed theoretically. Within the Lagrange coordinates and using the Maxwell and hydrodynamics equations, a wave equation describing the relativistic spherical wave is derived. The damped oscillating spherical wave solution is obtained analytically using the perturbation theory. Because of the coupled effects of spherical geometry,thermal pressure, and collision effect, the electron damps the periodic oscillation. The oscillation frequency and the damping rate of the wave are related to not only the collision and thermal pressure effect but also the space coordinate. Near the center of the sphere, the thermal pressure significantly reduces the oscillation period and the damping rate of the wave, while the collision effect can strongly influence the damping rate. Far away from the spherical center, only the collision effect can reduce the oscillation period of the wave, while the collision effect and thermal pressure have weak influence on the damping rate.

The Instability of Terahertz Plasma Waves in Two Dimensional Gated and Ungated Quantum Electron Gas

The instability of terahertz（THz）plasma waves in two-dimensional（2D）quantum electron gas in a nanometer field effect transistor（FET）with asymmetrical boundary conditions has been investigated.We analyze THz plasma waves of two parts of the 2D quantum electron gas：gated and ungated regions.The results show that the radiation frequency and the increment（radiation power）in 2D ungated quantum electron gas are much higher than that in 2D gated quantum electron gas.The quantum effects always enhance the radiation power and enlarge the region of instability in both cases.This allows us to conclude that 2D quantum electron gas in the transistor channel is important for the emission and detection process and both gated and ungated parts take part in that process.

Effect of High-Frequency Electric Field on Propagation of Electrostatic Wave in a Non-Uniform Relativistic Plasma Waveguide

The effect of a high frequency （HF） electric field on the propagation of electrostatic wave in a 2D non-uniform relativistic plasma waveguide is investigated. A variable separation method is applied to the two-fluid plasma model. An analytical study of the reflection of electrostatic wave propagation along a magnetized non-uniform relativistic plasma slab subjected to an intense HF electric field is presented and compared with the case of a non relativistic plasma. It is found that, when the frequency of the incident wave is close to the relativistic electron plasma frequency, the plasma is less reflective due to the presence of both an HF field and the effect of relativistic electrons. On the other hand, for a low-frequency incident wave the reflection coefficient is directly proportional to the amplitude of the HF field. Also, it is shown that the relativistic electron plasma leads to a decrease in the value of reflection coefficient in comparison with the case of the non relativistic plasma.

Determination of Instantaneous Frequencies of Low Plasma Waves in the Magnetosheath Using Empirical Mode Decomposition (EMD) and Hilbert Transform (HT)

The observations of in-situ spacecraft mission in the magnetosheath and a region of thermalized subsonic plasma behind the bow shock reveal a non-linear behaviour of plasma waves. The study of waves and optics in Physics has given the understanding of the effect of many waves coming together to form a wave field or wave packet. The common aspect of such study shows that two or more waves can superimpose constructively or destructively. The sudden high magnetic field data in the magnetosheath displays such possibility of superposition of waves. In this paper, we use the empirical mode decomposition (EMD) and Hilbert transform (HT) techniques to determine the instantaneous frequencies of low frequency plasma waves in the magnetosheath. Our analysis has shown that the turbulent behavior of magnetic field in the magnetosheath within the selected period is due to superposition of waves.

Collapse of Nonlinear Dust Sound Pulses in Cylindrical Dusty Plasma Waveguides

Nonlinear monopulses of dust sound waves in cylindrical dusty plasma waveguides bounded by a dielectric are investigated. The dusty plasma includes the positive ions as a light component and the negative dust as a heavy one. The dusty plasma with different masses of dust particles is considered. The set of hydrodynamic equations for the dust jointly with the Poisson one are used. The Boltzmann distribution is valid for the ions. The boundary conditions are applied at the smooth interface. When the moderate volume nonlinearity manifests, near the interface the variations of the dust concentration reach extremely high values, and the collapse of the dust sound waves occurs. In the cylindrical waveguides the collapse manifests at the values of the initial wave amplitudes essentially smaller than in the planar geometry. When the particles of lower masses are near the interface, the collapse realizes more rapidly.

Single Mode Periodic Wave Trains in Self-Gravitating Dusty Plasma

In this paper, we consider the dynamics of modulated waves in an unmagnetized, non-isothermal self-gravitating dusty plasma model. The varying charge on the moving dust, as it moves in and out of regions of differing electron and ion densities (due to changes in the electrostatic potential), will be out of phase with the equilibrium charge. The effect of the dust is to increase the phase velocity of the ion-acoustic (IA) waves i.e. decrease the Landau damping. In the low-amplitude limit and weak damping, we apply the reductive perturbation method on the model that resulted to the complex cubic Ginzburg-Landau (CCGL) equation. From these results, it is observed that, the plasma parameters strongly influence the properties of the solitary wave solution namely, the amplitude and the width. The effects of non-isothermal electrons, gravity, dust charge fluctuations and drifting motion on the ion-acoustic solitary waves are discussed with application in astrophysical contexts. It is also observed that the number of charges residing on the dust grains increases the modulational stability of the plane waves in the plasma, thus, enhancing the generation of modulated waves.

Low-Frequency Waves in Cold Three-Component Plasmas

The dispersion relation and electromagnetic polarization of the plasma waves are comprehensively studied in cold electron, proton, and heavy charged particle plasmas. Three modes are classified as the fast, intermediate, and slow mode waves according to different phase velocities. When plasmas contain positively-charged particles, the fast and intermediate modes can interact at the small propagating angles, whereas the two modes are separate at the large propagating angles. The near-parallel intermediate and slow waves experience the linear polarization, circular polarization, and linear polarization again, with the increasing wave number. The wave number regime corresponding to the above circular polarization shrinks as the propagating angle increases. Moreover, the fast and intermediate modes cause the reverse change of the electromagnetic polarization at the special wave number. While the heavy particles carry the negative charges, the dispersion relations of the fast and intermediate modes are always separate, being independent of the propagating angles. Furthermore, this study gives new expressions of the three resonance frequencies corresponding to the highly-oblique propagation waves in the general three-component plasmas, and shows the dependence of the resonance frequencies on the propagating angle, the concentration of the heavy particle, and the mass ratio among different kinds of particles.

Progress of Pattern Dynamics in Plasma Waves

This paper is concerned with the pattern dynamics of the generalized nonlinear Schrodinger equations(NSEs)relatedwith various nonlinear physical problems in plasmas.Our theoretical and numerical results show that the higher-order nonlinear effects,acting as a Hamiltonian perturbation,break down the NSE integrability and lead to chaotic behaviors.Correspondingly,coherent structures are destroyed and replaced by complex patterns.Homoclinic orbit crossings in the phase space and stochastic partition of energy in Fourier modes show typical characteristics of the stochastic motion.Our investigations show that nonlinear phenomena,such as wave turbulence and laser filamentation,are associated with the homoclinic chaos.In particular,we found that the unstable manifolds W(u)possessing the hyperbolic fixed point correspond to an initial phase θ=45° and 225° ,and the stable manifolds W(s)correspond toθ=135° and 315° .

Influence of air pressure on mechanical effect of laser plasma shock wave

The influence of air pressure on mechanical effect of laser plasma shock wave in a vacuum chamber produced by a Nd：YAG laser has been studied. The laser pulses with pulse width of 10ns and pulse energy of about 320mJ at 1.06μm wavelength is focused on the aluminium target mounted on a ballistic pendulum, and the air pressure in the chamber changes from 2.8 × 10^ 3 to 1.01 × 10^5pa. The experimental results show that the impulse coupling coefficient changes as the air pressure and the distance of the target from focus change. The mechanical effects of the plasma shock wave on the target are analysed at different distances from focus and the air pressure.

A numerical simulation of surface wave excitation in a rectangular planar-type plasma source

The principle of surface wave plasma discharge in a rectangular cavity is introduced simply based on surface plasmon polariton theory. The distribution of surface-wave electric field at the interface of the plasma-dielectric slab is investigated by using the three-dimensional finite-difference time-domain method （3D-FDTD） with different slotantenna structures. And the experimental image of discharge with a novel slot antenna array and the simulation of the electric field with this slot antenna array are both displayed. Combined with the distribution of surface wave excitation and experimental results, the numerical simulation performed by using 3D-FDTD is shown to be a useful tool in the computer-aided antenna design for large area planar-type surface-wave plasma sources.

Self-consistent three-dimensional modeling and simulation of large-scale rectangular surface-wave plasma source

A self-consistent and three-dimensional （3D） model of argon discharge in a large-scale rectangular surface-wave plasma （SWP） source is presented in this paper, which is based on the finite-difference time-domain （FDTD） approximation to Maxwell＇s equations self-consistently coupled with a fluid model for plasma evolution. The discharge characteristics at an input microwave power of 1200 W and a filling gas pressure of 50 Pa in the SWP source are analyzed. The simulation shows the time evolution of deposited power density at different stages, and the 3D distributions of electron density and temperature in the chamber at steady state. In addition, the results show that there is a peak of plasma density approximately at a vertical distance of 3 cm from the quartz window.

perimental Study on the Interaction of Electromagnetic Waves and Glow Plasma

An experimental system was established in order to study the interaction between electromagnetic waves, with a frequency of 300 kHz to 3 GHz, and DC glow discharge plasma. The results show that the DC glow discharge plasma affects the transmission properties of elec- tromagnetic waves, while the waves can change both temperature and density of electrons.

Electromagnetic interaction between local surface plasmon polaritons and an atmospheric surface wave plasma jet

We analyze the electromagnetic interaction between local surface plasmon polaritons （SPPs） and an atmospheric surface wave plasma jet （ASWPJ） in combination with our designed discharge device. Before discharge, the excitation of the SPPs and the spatial distribution of the enhanced electric field are analyzed. During discharge, the critical breakdown electric field of the gases at atmospheric gas pressure and the surface wave of the SPPs converted into electron plasma waves at resonant points are studied. After discharge, the ionization development process of the ASWPJ is simulated using a two- dimensional fluid model. Our results suggest that the local enhanced electric field of SPPs is merely the precondition of gas breakdown, and the key mechanism in maintaining the discharge development of a low-power ASWPJ is the wave-mode conversion of the local enhanced electric field at the resonant point.

WIND observations of plasma waves inside the magnetic cloud boundary layers

Based on the WIND observational data for the plasma waves from thermal noise receptor (TNR) working on the frequency 4―256 kHz and the solar wind and the magnetic fields, we analyze the plasma wave activities in the 60 magnetic cloud’s boundary layers (BLs) and find that there are often various plasma wave activities in the BLs, which are different from those in the adjacent solar wind (SW) and the magnetic clouds (MC). The basic characteris-tics are that: (1) the enhancement of the Langmuir wave near the electronic plasma frequency (fpe) is a dominant wave ac-tivity, which occupies 75% investigated samples; (2) the events enhanced both in the langmuir and ion acustic (f < fpe) waves are about 60% of investigated samples; (3) broadband, continuous enhancement events in the plasma wave activities were observed in the whole frequency band of TNR, and about 30% of the 60 samples, however, were not observed in the SW and the MC investigated events; (4) although the ratio of the temperatures between the electon and proton, Te/Tp≤1, the ion caustic wave enhancement activities are still often observed in the BLs, which makes it difficult to ex- plain them by the traditional plasma theory. New results reported in this paper further show that the magnetic cloud’s BL is an important dynamic structure, which could provide useful diagnosis for understanding the cloud’s BL physics and could expand a space developing space plasma wave theory.

Development of a helicon-wave excited plasma facility with high magnetic field for plasma-wall interactions studies

The high magnetic field helicon experiment system is a helicon wave plasma（HWP）source device in a high axial magnetic field（B0）developed for plasma–wall interactions studies for fusion reactors.This HWP was realized at low pressure（5×10^-3-10 Pa）and a RF（radio frequency,13.56 MHz）power（maximum power of 2 k W）using an internal right helical antenna（5 cm in diameter by 18 cm long）with a maximum B0of 6300 G.Ar HWP with electron density～10^18–10^20m^-3 and electron temperature～4–7 e V was produced at high B0 of 5100 G,with an RF power of 1500 W.Maximum Ar^＋ion flux of 7.8×10^23m^-2s^-1 with a bright blue core plasma was obtained at a high B0 of 2700 G and an RF power of 1500 W without bias.Plasma energy and mass spectrometer studies indicate that Ar^＋ ion-beams of 40.1 eV are formed,which are supersonic（～3.1cs）.The effect of Ar HWP discharge cleaning on the wall conditioning are investigated by using the mass spectrometry.And the consequent plasma parameters will result in favorable wall conditioning with a removal rate of 1.1×10^24N2/m^2 h.

Shadowgraph investigation of plasma shock wave evolution from Al target under 355-nm laser ablation

The propagation of a plasma shock wave generated from an Al target surface ablated by a nanosecond Nd：YAG laser operating at 355 nm in air is investigated at the different focusing positions of the laser beam by using a time-resolved shadowgraph imaging technique. The results show that in the case of a target surface set at the off-focus position, the condition of the focal point behind or in front of the target surface greatly influences the evolution of an Al plasma shock wave, and an ionization channel forms in the case of the focal point set in front of the target surface. Moreover, it is found that the shadowgraph with the evolution time around 100 ns shows that a protrusion appears at the front tip of the shock wave if the focal point is at the target surface. In addition, the calculated results of the expanding velocity of the shock wave front, the mass density, and pressure just behind the shock wave front are presented based on the shadowgraphs.