Chengxun Yuan

Reflection Properties of Electromagnetic Wave in a Bounded Plasma Slab

A bounded plasma stealth model is proposed in this paper. The method of impedance transformation with multiple dielectrics is used to study the propagation properties of electromagnetic (EM) waves in this plasma slab. The relations between the plasma parameters and the reflection which is a combination of the power reflected from the wall-plasma interface, the partial reflections from the bulk plasma, and the collisionally attenuated waves reflected by the conductive plane are derived. In addition, the reflections of the incident wave power dependence on the thickness of plasma are presented for different incident wave frequencies and various plasma parameters. The numerical calculation results show that, due to the presence of the walls, the mechanism of EM-wave attenuation is a combination of the collisional absorption and cavity resonance effects. It is demonstrated that detailed numerical analyses are useful in practical applications pertaining to the control of the reflection of EM waves through a uniform plasma slab covering the conductive plane.

Properties of Propagation of Electromagnetic Wave in a Multilayer Radar-Absorbing Structure With Plasma- and Radar-Absorbing Material

A multilayer radar-absorbing structure with plasma- and radar-absorbing material (RAM) is established to investigate the stealth mechanisms of the multilayer absorber. The method of impedance transformation with multiple dielectrics is used to analyze the propagation of electromagnetic (EM) waves in the multilayer structure. The dependences of EM waves attenuation on the parameters of the plasma and RAMs are provided. The numerical results indicate that generally speaking, the joint attention effect of RAM and plasma is better than the effect of either RAM or plasma solely. The attenuation of an EM wave in the structure is strongly affected by: a) the characteristics of RAMs; b) the width of the plasma layer; c) the parameters of the outer layer material; d) the electron density of the plasma; and e) the collision frequency between electrons and neutrals. It is demonstrated that detailed numerical analyses are useful in practical applications pertaining to the control of the reflection of EM waves through a multilayer radar-absorbing structure with plasma and RAMs.

Propagation of broadband terahertz pulses through a dense-magnetized-collisional-bounded plasma layer

The terahertz characteristics of a dense-magnetized-collisional-bounded plasma under normal incident are analyzed in this study, which is of practical significance in plasma diagnostics with electromagnetic waves. We theoretically calculate the reflection, absorption, and transmission coefficients for right- and left-handed polarized terahertz waves through a uniform, magnetized, and collisional plasma slab bounded by lossless transparent walls. The power absorption spectra in the frequency range of 0.1-2 THz are given with strong external magnetic fields and different plasma parameters such as plasma density and collisional frequency. Our numerical result is consistent with Jamisons experimental result. It is found that plasma absorption is mainly caused by the collisional absorption and electron cyclotron resonance. Furthermore, the absorption heavily depends on the polarization mode of the terahertz waves when the external magnetic field B is high enough that the election gyrofrequency is near the incident wave frequency. The relationships between the corresponding parameters of the problem are studied numerically.

Self-focusing and defocusing of Gaussian laser beams in plasmas with linear temperature ramp

The propagation characteristics of the Gaussian laser beam in plasmas in the presence of a linear electron temperature ramp have been investigated by taking the electron temperature as an individual variable. The ponderomotive force and collision have been considered as the mechanisms of nonlinearity. The second order differential equation of the dimensionless beam-width parameter has been acquired and solved with several initial electron temperatures and plus-minus temperature ramp parameters. The propagation regimes of laser beam are found to be sensitive with the selection of electron temperature. The linear temperature ramp breaks the stationary propagating mode and enhances the self-focusing or defocusing propagation properties. Results indicate the feasibility of extended propagation of focused laser beam in plasmas by modifying the electron temperature.

Visible light broadband perfect absorbers

The visible light broadband perfect absorbers based on the silver (Ag) nano elliptical disks and holes array are studied using finite difference time domain simulations. The semiconducting indium silicon dioxide thin film is introduced as the space layer in this sandwiched structure. Utilizing the asymmetrical geometry of the structures, polarization sensitivity for transverse electric wave (TE)/transverse magnetic wave (TM) and left circular polarization wave (LCP)/right circular polarization wave (RCP) of the broadband absorption are gained. The absorbers with Ag nano disks and holes array show several peaks absorbance of 100% by numerical simulation. These simple and flexible perfect absorbers are particularly desirable for various potential applications including the solar energy absorber.

Beam steering in a nonlocal medium with inhomogeneous nonlinearity

We address the dynamics of out-of-phase soliton pairs and dipole solitons in a nonlocal medium with inhomogeneous nonlinearity, and demonstrate their self-splitting into two individual solitons. We reveal that this self-splitting strongly depends on the variation of the longitudinal nonlinearity and it can be employed for efficient control of the soliton trajectories. We also demonstrate that the index waveguide, which is induced by the soliton pairs and the dipole soliton bound state, yields a family of special waveguides and beam splitters for trapped linear beams. Interestingly, the switching efficiency of this beam splitter could be controlled by adjustment of the longitudinal nonlinearity.