Presence Of Plasma Resonance Research Articles

Hydrodynamic Study of Terahertz Three-Dimensional Plasma Resonances in InGaAs Diodes

We investigate the presence of plasma resonances in InGaAs n+−n−n+ diodes under different optical excitation conditions. In particular, we study the case of diodes submitted to an optical photoexcitation presenting a beating in the terahertz frequency domain. For this purpose, we calculate the electric field response in the middle of the n and n+ regions using a hydrodynamic approach self-consistently coupled to a one-dimensional Poisson solver. In particular, the analysis of the electric field response to an optical beating as a function of the doping and the geometry of the devices allows us to evidence in all the considered cases the presence of resonances in both n and n+ regions. However, while the observed resonances agree with the theoretical 3D plasma frequency in the n+ external regions, we point out a shift towards higher frequencies in the n region. We show that this shift towards the n+ 3D plasma frequency is due to the strong coupling between the two region modes, and tends to disappear when the n region lengthens, whereas the influence of the n+ regions length on the resonance frequency is negligible. Moreover, we show that the amplitude of the plasma resonances can be enhanced at high doping levels and by increasing the level of the optical photoexcitation. The obtained results show clearly that the resonances associated with 3D plasma waves in InGaAs diodes lie in the THz domain for typical values of dopings and lengths, thus opening new possibilities to exploit not only field effect transistors but also diodes as solid-state terahertz devices operating at room temperature.

Modeling of microwave discharges in the presence of plasma resonances.

This study presents a kinetic model of microwave generated discharges sustained, under the conditions of a diffusion controlled regime, by the propagation of azimuthally symmetric surface waves. The effect of the plasma resonances, which can appear over the radial density profile in the vicinity of the walls and lead to sharp peaks in the radial component of the high-frequency wave electric field in the plasma, is introduced. This effect modifies the surface wave damping and results in a collisional as well as collisionless (quasilinear) transfer of energy from the radial field component to the plasma. In the Boltzmann equation the latter appears as a third channel of energy transfer, which is added to the Joule heating by the axial and radial wave field components. The spatially inhomogeneous Boltzmann equation for the electron-energy distribution function, which accoutns for the radial ambipolar field, is solved in the nonlocal approximation. A complete set of relations is formed by simultaneous consideration of the fluid equations for the ion motion and the field equations for the surface wave electric field. The problem is solved numerically. It yields self-consistent radial electron density profiles and radial electric field distributions. The obtained solutions evidence indeed the occurrence of plasma resonances. The study is extended also to obtaining results for the axial variation of the (radially averaged) electron density. It turns out that the widely used concept of approximate constancy of wave power absorbed by one electron in a diffusion controlled regime keeps its validity also in the presence of plasma resonances and of the corresponding collisional, as well as collisionless, power transfer to the plasma in the resonance regions.

Transition radiation of a charge in a thin inhomogeneous plasma layer

The authors study the resonant transition radiation of a uniformly moving charge in a thin parabolic plasma layer; the transition radiation is caused by the presence of plasma resonance near the extremum of concentration. It is shown that, in a narrow frequency interval near the maximum plasma frequency of the layer, the spectral energy density of the extremal resonant transition radiation exceeds considerably the energy density of radiation, although the total energies of transition radiation are, in both cases, close in magnitude. We consider the possibilities of using this effect for the diagnostics of inhomogeneous plasma.

Quasi-static theory of an antenna in a magnetoactive plasma in the presence of plasma resonance

Quasi-static theory of an antenna in a magnetoactive plasma in the presence of plasma resonance

Electron Density Distribution in a High Frequency Discharge in the Presence of Plasma Resonance

In a high frequency discharge plasma resonance maximizes the electric field, thus producing a high ionization rate in the regions near resonance. The effect of this on the distribution of electrons and of ionization in a parallel plane discharge is calculated and compared with the observation that the light from such a discharge often is a minimum at the center.