Nonlinear Electron Plasma Oscillations Research Articles

Terahertz-frequency plasmonic-crystal instability in field-effect transistors with asymmetric gate arrays

We present a theory for plasmonic crystal instability in a semiconductor field-effect transistor with a dual grating gate array, designed with strong asymmetry in the elementary cell of this “crystal”. We demonstrate that, under the action of a dc current bias, the Bloch plasma waves in the plasmonic crystal formed in this transistor develop the Dyakonov–Shur instability. By calculating the energy spectrum and instability increments/decrements—which govern the growth/decay of excitations within the plasmonic crystal—we analyze the dependence of the latter on the electron drift velocity and the extent of the structural asymmetry. In contrast with the corresponding problem for gate arrays with symmetric unit cells, the presence of finite plasma instability increments across the entire Brillouin zone is established. This important difference points to the possibility of exciting sustained, radiating, non-linear electron plasma oscillations in the instability endpoint of the asymmetric array. These structures should be readily implementable in common semiconductor heterostructures, using standard nanofabrication techniques, enabling operation at room temperature. Long-range coherence of the unstable plasma oscillations, generated in the elementary cells of the crystal, should dramatically increase the radiated THz electromagnetic power, making this approach a promising pathway to the generation of THz signals.

A coupled pseudoforce model for quantum plasmon excitations

A coupled nonlinear pseudoforce system is derived from hydrodynamic equations for the nonlinear electron plasma oscillations in an electron-ion plasma with arbitrarily degenerate electron fluid in a background fixed ion potential. The dynamics of the fully nonlinear electron plasma excitations are studied using this generalized coupled pseudoforce model including the damping and driving pseudoforce elements. The fully nonlinear plasma oscillations are shown to be of quite different nature in the extreme classical and quantum limits. In particular, high frequency quantum oscillations due to electron tunneling effect modulates the ordinary large amplitude low frequency periodic Langmuir excitations in the quantum plasma regime. It is shown that such characteristic quantum oscillations appear due to the electron wavefunction overlap which also appear on the quantum shock wave structures. It is found that the stimulation of dense plasmas with the driving frequency matching that of characteristic quantum oscillations leads to the chaotic behavior of the electron fluid. The presented coupled pseudoforce theory can be used to investigate a large number of interesting nonlinear phenomena such as the quantum electron fluid chaos and turbulence, autoresonance phenomenon, quantum harmonic generation, nonlinear resonances, and bistability of quantum electron plasma oscillations.

A novel numerical scheme for nonlinear electron plasma oscillations

In this work, we suggest an easy-to-code higher-order finite volume semi-discrete scheme to analyze the nonlinear behavior of the electron-plasma oscillations by the direct numerical simulation of electron fluid equations. The present method employs a fourth-order accurate centrally weighted essentially nonoscillatory reconstruction polynomial for estimating the numerical flux at the grid-cell interfaces, and a fourth-order Runge-Kutta method for the time integration. The numerical implementation is validated by reproducing earlier results for both non-dissipative and dissipative cold plasmas. The stability of the present scheme is illustrated by evolving the nonlinear electron plasma oscillations in a cold non-dissipative plasma for hundred plasma periods, which also display a negligible numerical dissipation. Moreover, the fourth-order accuracy of the existing approach is confirmed by evaluating the convergence of errors for nonlinear electron plasma oscillations in a cold non-dissipative plasma.

Fluid Turbulence in Quantum Plasmas

Nonlinear fluid simulations are developed by us to investigate the properties of fully developed two-dimensional (2D) electron fluid turbulence in a very dense Fermi (quantum) plasma. We find that a 2D quantum electron plasma exhibits dual cascades, in which the electron number density cascades towards smaller turbulent scales, while the electrostatic potential forms larger scale eddies. The characteristic turbulent spectrum associated with the nonlinear electron plasma oscillations (EPO) is determined critically by a ratio of the energy density of the EPOs and the electron kinetic energy density of quantum plasmas. The turbulent transport corresponding to the large-scale potential distribution is predominant in comparison with the small-scale electron number density variation, a result that is consistent with the classical diffusion theory.

Phase mixing due to ion motion and relativistic effects in nonlinear plasma oscillations

Nonlinear electron plasma oscillations in a cold-plasma have been studied numerically using one-dimensional (1D) Vlasov–Poisson equations. It is shown that both ion motion and the relativistic effect of electron motion can lead to phase mixing phenomena even if a plasma oscillation is at a moderate amplitude. When its amplitude is relatively small, the phase mixing is mainly caused by the ion motion. When its amplitude is large, the relativistic effect of electrons is dominant. The nonlinear process caused by the relativistic effect depends significantly upon the phase velocity of the plasma oscillation, while that caused by the ion motion depends weakly upon its phase velocity.

Frequency Increase and Damping of Nonlinear Electron Plasma Oscillations in Cylindrical Symmetry

Radial electron plasma oscillations excited by a laser wake field are measured by frequency domain interferometry. In the nonlinear regime we observe two important effects: (i) an increase of the oscillation frequency and (ii) the damping of the oscillation in a few plasma periods. Simulations show that this last effect is related to the presence of a steep radial density gradient near the focus edge. {copyright} {ital 1997} {ital The American Physical Society}

Nonlinear oscillations in a warm plasma.

Nonlinear electron plasma oscillations in a warm plasma are studied by use of Lagrangean coordinates. Without recourse to amplitude expansion, the electron density is obtained as an explicit function of space and time. In the zero-temperature limit, a restriction on the previously found cold-plasma solutions is found.

Cold plasma wavebreaking in the presence of an electromagnetic driver

Nonlinear electron plasma oscillations driven by an electromagnetic wave are investigated. An improved, self-consistent Lagrangian description of the resonant interaction is derived. The modifications to the simple capacitor plate or uniform electrostatic driver model previously employed are calculated and shown to have a negligible effect on the wavebreaking process for laser intensities I<1017 W cm−2 in the case of Nd lasers.

Non-linear electron plasma oscillations: comments on recent developments, and non-linear frequency shift for the water bag model

A recent paper (see Numano, ibid., vol.17, p.961 (1975)) on the application of the Von Mises transformation to the non-linear one-dimensional electron plasma oscillation problem is commented on, completed and corrected. The frequency shift is computed for a water bag model, valid for all k, and found in excellent agreement with the results of computer experiments.

Nonlinear plasma oscillations in terms of multiple-water-bag eigenmodes

The problem of nonlinear electron plasma oscillations is considered, using the water-bag model with N bags, and involving second-order expansions of the electric field. The solutions are readily obtained and are successfully checked by computer experiment.

Cold plasma wavebreaking: Production of energetic electrons

Nonlinear electron plasma oscillations are investigated in the wavebreaking regime where collective energy is converted into random energy. The Lagrangian description of the electrons is extended beyond fluid element orbit crossing, thereby exposing the essential physics of wavebreaking and permitting simple analytical interpretation of it. In driven cold inhomogeneous plasma a region of large resonant oscillations decays by producing energetic electrons which escape into the less dense plasma. The maximum energy of the fast electrons produced during the driver period in which the first wave breaks is much larger than the energy of an electron oscillating freely in the driver field. The total energy of the fast electrons exceeds that supplied the system by the driver in a period and can be a significant fraction of the total energy in the oscillations at the onset of wavebreaking.