Soliton control in inhomogeneous nonlocal media

In this paper, we have addressed a new way to achieve soliton control, such as compression (or broadening) and fission. More concretely, nonlocality management technique has been adopted, and different control purposes can be realized by controlling corresponding nonlocal parameter. Essentially, nonlocality management should be classified into nonlinearity management.     

Vortex solitons with inhomogeneous polarization in nonlocal self-focusing nonlinear media

Both azimuthally and radially polarized vortex solitons are investigated to be able to exist in highly nonlocal nonlinear media. We get exactly analytical solutions of azimuthally polarized vortex solitons with only polarization singularities and radially polarized vortex solitons with both phase singularities and polarization singularities. Both azimuthally and radially polarized vortex solitons can exist in nonlocal self-focusing nonlinear media with proper modulation of the beam power and the degree of nonlocality. Contrary to those of radially polarized counterparts in local Kerr media, the topological charge can be any integer. When the topological charge m ≠ 0, both phase singularities and polarization singularities work. When m = 0, the polarization singularities work. Azimuthally polarized vortex solitons with polarization singularities corresponds to the linearly polarized vortex solitons with single charge. Our results show that polarization singularities work the same way as phase singularities in some sense.     

Computer-generated space-variant polarization elements with subwavelength metal stripes

A novel method of performing two-dimensional space-variant polarization operations is presented. The method is based on determining the local direction and period of subwavelength metal-stripe gratings by use of vectorial optics to obtain any desired continuous polarization change. We demonstrate our approach with specific computer-generated space-variant polarization elements for laser radiation at 10.6mum. The polarization properties are verified with complete space-variant polarization analysis and measurement.     

A fast linearized pseudo-spherical two orders of scattering model to account for polarization in vertically inhomogeneous scattering-absorbing media

We calculate the reflection matrix for the first two orders of scattering in a vertically inhomogeneous, scattering-absorbing medium. We take full account of polarization and perform a complete linearization (analytic differentiation) of the reflection matrix with respect to both the inherent optical properties of the medium and the surface reflection condition. Further, we compute a scalar-vector correction to the total intensity due to the effect of polarization; this correction is also fully linearized. The solar beam attenuation has been computed for a pseudo-spherical atmosphere.Results from the two orders of scattering (2OS) model have been tested against scalar intensities for an inhomogeneous atmosphere, and against Stokes vector results for a homogeneous atmosphere. We have also performed backscatter simulations of reflected sunlight in the O₂A band for a variety of geometries, and compared our results with those from a full vector multiple scattering code. Our results are exact in the center of strong lines and most inaccurate in the continuum, where polarization is least significant. The s- and p-polarized radiances are always computed very accurately. The effect of gas absorption optical depth, solar zenith angle, viewing geometry, surface albedo and wind speed (in the case of ocean glint) on the intensity, polarization and corresponding weighting functions have been investigated. It is shown that the 2OS model provides fast and reliably accurate polarization corrections to the scalar-model radiance and weighting function fields. The model can be implemented in operational retrieval algorithms as an adjunct radiative transfer code to deal with polarization effects.     

Diffusion in inhomogeneous media

The problem is to establish the correct diffusion equation in a medium that is inhomogeneous and whose temperature also varies in space. As a special model we study particles whose phase space distribution obeys Kramers' equation with a generalized collision operator. In the usual limit of strong collisions a diffusion equation is obtained. This equation contains additional drift terms, which depend on the form of the collision operator. They cannot be expressed as a mobility and a diffusion coefficient, unless the decay law of the velocity happens to be linear. Conclusion: no universal form of the diffusion equation exists, but each system has to be studied individually.Dedicated to Professor Harry Thomas on the occasion of his 60th birthday     

Onsager relations for transport in inhomogeneous media

The nonlinear equations that describe transport in inhomogeneous media cannot be obtained by a straightforward extension of the known phenomenological equations for homogeneous media. One cannot therefore asserta priori that the Onsager reciprocity relations remain valid. Previously the correct equations have been obtained for three special models using kinetic theory. It is here shown that in these models the Onsager relations do indeed hold, provided that they are formulated with care.     

Generation of vector beam with space-variant distribution of both polarization and phase

We present an idea to generate an arbitrary space-variant vector beam with structured polarization and phase distributions. The vector beams are synthesized from the left- and right-hand polarized light, each carrying different phase distributions. Both the phase and the state of polarization of vector beams can be tailored independently and dynamically by a spatial light modulator.     

Exact solutions for electromagnetic waves in inhomogeneous media

Exact solutions of the wave equation for the propagation of electromagnetic waves in some inhomogeneous media are found. The first solution corresponds to the barometric model of the atmosphere, whose index of refraction can be expressed by the formulaN ²(z)=1+(N ₀ ² -1) exp (–z/z ₀). The other cases correspond toN ²(z)=1+(N ₀ ² -1) ch^–2(z) andN ²(z)=a-b. [1+exp(z/L)]^–1.Dedicated to Academician Vladimír Hajko on the occasion of his 65th birthday.     

Radio-wave tomography of inhomogeneous media

Results of experimental investigations on radar sensing of inhomogeneous media and objects with the use of both superbroadband (from 0.5 to 17 GHz) multifrequency scanning and supershort nanosecond and subnanosecond radar pulses are considered. It is demonstrated that addition of angular and spatial scanning and subsequent synthesis of a large aperture allow a three-dimensional tomography of low-contrast inhomogeneities to be realized with a spatial resolution of about 1 cm. Examples are presented that confirm a high efficiency of the method for contactless tomography of the forest structure and detection and visualization of infantry mines below a rough sand surface. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 20–25, September, 2006.     

Optical properties of inhomogeneous media

A theory is presented for the optical properties of inhomogeneous media consisting of small particles in a continuous dielectric host. In contrast to the commonly used Maxwell-Garnett approach, our theory includes the dipole-dipole coupling between the randomly distributed particles. The pronounced disorder-induced broadening explains the large width of typical experimental absorption lines and thus resolved the long-standing discrepancy between measured spectra and the predictions of the Maxwell-Garnett model.     

Alfven-wave scattering in inhomogeneous media

Alfven-wave scattering by inhomogeneities of the permittivity tensor (r) is examined. The scattering index , phase velocity v*, and group velocity c* are calculated over the entire wavelength range. Asymptotic formulas for , v*, and c* are derived for long (as compared with scatterer size), short, and ultrashort wavelengths.Moscow Institute of Electronic Engineering. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 35, No. 5, pp. 421–432, May, 1992.     

Oscillatory waves in inhomogeneous neural media

In this Letter we show that an inhomogeneous input can induce wave propagation failure in an excitatory neural network due to the pinning of a stationary front or pulse solution. A subsequent reduction in the strength of the input can lead to a Hopf instability of the stationary solution resulting in breatherlike oscillatory waves.