Plasma effect

Abstract: We propose and demonstrate a new type of optical nonlinearity based on the properties of the DX center in doped compound semiconductors. We report measurements on samples of AlGaAs:Si which were exposed to interfering laser beams and find diffraction from a large, persistent refractive index change associated with the well‐known persistent photoconductivity effect in this material. The new effect is shown to exhibit a refractive index change 30 times larger than that of conventional photorefractive materials. We explain the origin of the refractive index change in terms of the plasma effect and show that its expected magnitude is consistent with our observations.

Abstract: Studies on the propagation of high power microwave and its interaction with a plasma in a metallic waveguide are carried out. For this we consider the fundamental TE10 mode that propagates in an evacuated rectangular waveguide and encounters a plasma which is filled in another waveguide of the same size. Using Maxwell’s equations we evaluate the field components of the mode in the evacuated waveguide and then obtain coupled differential equations for the field components of the mode in the plasma filled waveguide, where the plasma effect enters in terms of its dielectric constant. These equations are solved numerically using the fourth-order Runge–Kutta method for the electric field amplitude of the microwave and its wavelength under the effect of plasma density, waveguide width, and microwave frequency. All the investigations are carried out for different initial plasma density profiles, namely homogeneous density, linear density with gradient in the propagation direction and the density with Gaussian pr...

Abstract: This paper presents an investigation of the propagation characters of Gaussian laser beam in cold collisionless plasma by considering the plasma temperature variation. The ponderomotive nonlinearity is involved and induces the nonlinear self-focusing against spatial diffraction. The second-order differential equation of dimensionless beam width parameter f(ξ) in terms of plasma temperature is established from Maxwell’s equations with paraxial approximation. The initial (P0,ρ0) plane, behaviors of f(ξ) parameter, and perturbed density n/nn0 n0 of different plasma temperatures are plotted and analyzed. The plasma temperature is divided into four regions, which leads to different propagation characters including oscillatory divergence, self-trapping, self-focusing, and steady divergence. The plasma density distribution modified by the electric field intensity and plasma temperature is discussed.

Abstract: Theoretical calculations of the third‐order susceptibility χ(3) in GaAs‐AlxGa1−xAs and Hg1−xCdxTe‐HgyCd1−yTe superlattices are reported. The conduction–band nonparabolicity effect and the photoexcited plasma effect are both considered.