(PR) crystals are photoconductive, specific doped electrooptics materials. When an optical beam propagates in a PR crystal, charge carriers are excited from photosensitive impurities into the conduction band where they move due to drift and diffusion and eventually are trapped in darker regions of the light intensity pattern. The resulting space-charge redistribution produces the spatially nonuniform internal electric field which in turn modulates the material refractive index through the linear electro-optic effect. Under an appropriate polarity of an external voltage, a local variation in the index of refraction leads to self-focusing or self-defocusing effect of an optical beam. This allows forming bright or dark soliton states when the nonlinearity compensates exactly the diffraction spreading of a light beam. As a result, the beam propagates in a PR medium without changing its transverse profile. For one-dimensional bright spatial solitons, a polarized optical beam in the form of a narrow stripe is launched at the entrance of a crystal together with orthogonally polarized background illumination. In the case of dark soliton, a black notch is superimposed on an otherwise uniform background illumination. Both types of solitons can be generated in the same crystal by reversing the bias voltage direction.Due to a possibility of soliton creation at very low laser power levels, and their potential applications in all optical switching devices, PR screening solitons have been subjected to intensive theoretical and experimental works for the last two decades. So far, the formation of (1 + 1)D solitary waves has been demonstrated experimentally in various PR materials such as ferroelectrics (SBN) [3][4][5], (LiNbO 3 ) [11,12], sillenities (BTO) [6,7], (BSO) [13] centrosymmetric paraelectrics (KLTN) [8], semiconductors (InP:Fe) [9,14], and (CdZnTe) [15] both in geometry with bulk PR crystals and in planar waveguides [10,16]. AbstractIn the present paper, the problem of one-dimensional screening photorefractive solitons is reconsidered in the context of the accordance of soliton solutions with the Kukhtarev-Vinetskii model. In all theoretical and experimental works dealing with the analysis of such type solitons, one assumes that under the slowly varying approximation for the optical field amplitude the reduced form of photorefractive rate equations can be employed. In this work, we point out that the crucial and commonly accepted approximation within this scheme has a limited range of applicability as regards dark solitons. This author proposes a relatively simple modification of the standard saturable photorefractive response formula to obtain the plausible self-consistent solutions. The improved solutions for screening black solitons have been derived and discussed by comparison with standard solutions.

A general approach to the approximate analytical solution of photorefractive transport equations for arbitrary fringe contrast is presented. The method based partially on the perturbative scheme permits us to find the stationary space–charge field distribution inside a photorefractive crystal for a two-wave mixing (TWM) geometry with a DC electric field. The method can be employed for various band transport models. In the present work two distinct electron–hole conduction models are investigated. The solutions are compared with the results of numerical calculations and good agreement is found.

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Części 1÷9 i 1÷10 Eurokodu 3 oraz PN-EN ISO 5817:2014 uporządkowały reguły projektowania konstrukcji stalowych narażonych na zmęczenie. Podane klasy zmęczeniowe FAT określono wg jednakowego algorytmu dla badanych elementów poziomu jakości B i C. W artykule wykazano, że algorytmu tego nie można stosować dla elementów starzonych oraz z niezgodnościami spawalniczymi, karbami poziomu jakości D i większymi. Wymagania dotyczące zmęczenia z części 1÷9 Eurokodu 3, podobnie jak udarności z części 1÷10, nie powinny dotyczyć konstrukcji eksploatowanych.

Nonlinear transport of hot electrons in semi-insulating GaAs / AlGaAs quantum wells significantly affects their photorefractive properties. In case of two waves mixing, this influence consists, among others, in an increased shift of photorefractive grating relative to light intensity distribution. The influence of nonlinear transport on grating recording time is less examined experimentally and theoretically. This study compares numerical and analytical solutions describing grating dynamics in approximation of small fringe contrast. The influence of nonlinear electron mobility on space-charge field was examined depending on external electric field intensity and on the grating constant. It was found that in the electric field range below 20 kV/cm, the nonlinear transport of electrons does not shorten the grating generation time.