Transformation of a Gaussian pulse upon reflection from a resonant thin film structure

Peculiarities of Gaussian pulse reflection from a thin film with a resonance frequency dependence of the permittivity on a substrate with material parameters not depending on frequency are studied. Results of numerical analysis of equations determining the light field distribution in the reflected pulse are presented. The effect of the angle of incidence, carrier frequency, and duration of the incident pulse on the shift and transformation of the reflected pulse envelope is considered.     

Gaussian pulse transformation upon reflection from a resonant medium

The transformation and longitudinal shift of “the center of gravity” of a Gaussian pulse reflected from the plane surface of a semi-infinite resonant medium are analyzed numerically. The regions of carrier frequencies in which the maximum and minimum deformations of the reflected pulse are observed are determined.     

The effect of ion motion on the reflection of an electromagnetic wave from plasma

An electromagnetic wave with electric vector parallel to the plasma boundary falls from a vacuum on a half-space filled with magnetoactive plasma and bounded by a particle-reflecting wall. A comparison is made of the effect of thermal motion of electrons and ions on the boundary, on the coefficient of reflection and on the absorbed energy.     

Propagation and reflection of an electromagnetic wave in a hot inhomogeneous plasma

Using the WKB method a local dispersion equation of a right-hand circularly polarized wave and an expression for its electric field are derived, the wave having frequency smaller than the electron cyclotron frequency and propagating in a hot inhomogeneous plasma. The density gradient of the plasma is constant and parallel to an external magnetostatic field. Further the reflection coefficient of this wave is derived.Stimulating discussions with Dr. J. Václavík are gratefully acknowledged.     

High-order harmonic generation by nonlinear reflection of an intense high-contrast laser pulse on a plasma

We demonstrate the use of a plasma mirror to obtain 60-fs 10-TW laser pulses with a temporal contrast of 10(8) on a nanosecond time scale and 10(6) on a picosecond time scale, and we use these high-contrast pulses to generate high harmonics by nonlinear reflection on a plasma with a steep electronic density gradient. Well-collimated harmonics up to 20th order are observed for a laser intensity of approximately equal to 3 x 10(17) W/cm2, whereas no harmonics are obtained without the plasma mirror.     

Laser pulse reflection by anisotropic plasma

The effect of anomalous amplification of test laser pulse reflected by a nonequilibrium plasma formed under atom ionization by a strong pulse of circularly polarized wave is described. It is shown that the gain in radiation intensity may reach ten orders of magnitude. The most effective amplification takes place for frequencies comparable with the Weibel instability growth rate.     

Self distortion of a Gaussian electromagnetic pulse in a plasma

On the basis of perturbation theory, the phenomenon of nonlinear self distortion of an electromagnetic pulse (Gaussian in time) in a collisional plasma has been studied. The nonlinearity appears through the modulation of electron collision frequency by the power absorption from the wave. At moderate energies of the pulse, considerable distortion in the amplitude envelope has been predicted.     

Features of femtosecond laser pulse reflection from a sharp boundary of relativistic laser plasma

The features of femtosecond laser pulse reflection from a plasma target of near-critical density were analytically and numerically studied in a wide range of laser pulse intensities and durations. Based on analytical calculations, it is shown that the pulse reflectance at a constant intensity decreases with decreasing pulse duration. Based of numerical simulation results, it is shown that, as a superintense femtosecond laser pulse is incident on a plasma layer with a concentration close to the critical one, a quasi-periodic electron-density structure is formed in the plasma bulk, which can both increase and decrease the the laser pulse reflectance.     

Effect of pulse entrapping on diffuse reflection from a resonant random medium: exact solution to the scalar albedo problem

A recently derived radiative transfer equation with three Lorentzian delay kernels is applied to an albedo problem of the scalar wave field produced by the diffuse reflection of a quasi-monochromatic pulse from a semi-infinite random medium consisting of resonant point-like scatterers. The albedo problem is solved exactly in terms of the Chandrasekhar H-function H(μλ), extended analytically into the complex single-scattering albedo λ plane. The resulting analytic solution for the time evolution of a diffusely reflected short pulse is used to study on the whole time axis the effect of the redistribution of the energy of the propagated pulse from the front to the rear of the pulse in cases where the pulse may for most of the propagation time through the medium be 'entrapped' inside resonant scatterers. By considering the power flux through unit area of the boundary of the medium and unit solid angle, it is shown that the relative shift of an 'energy centroid' ('centre of mass') of the pulse diffusely reflected from the resonant random medium (compared with the pulse energy centriod in the non-resonant case) is equal to the parameter describing the energy accumulation inside the scatterers. This result may be used for experimental study of resonant random media with the aid of a short-pulse technique.     

Reflection and transmission of an ultrashort electromagnetic pulse incident normal to a flat plasma layer

The process of reflection and transmission of ultrashort pulses incident normal to a flat plasma layer of finite thickness and on a step barrier is calculated within an exact mathematical approach for various parameters (barrier width and duration and carrier frequency of a corrected Gaussian pulse) of the problem.     

Analysis of the reflection of electromagnetic waves in an unsteady moving magnetized plasma slab

The reflection index of an unsteady moving magnetized plasma slab irradiated by an electromagnetic wave is investigated. The direction of the external magnetic field is parallel to the plasma surface and the electromagnetic wave is normally incident on a gas slab and produces the plasma. This gas slab is being ionized by another source and the density of the mentioned unsteady plasma increases with time. The effects of the density growth rate, velocity, thickness of the plasma slab, and the external magnetic field on the reflection index are simulated.