Nonstationary thermal self-action of partially coherent laser radiation

Nonstationary thermal self-action of laser radiation with limited spatial coherency is analyzed using the nonlinear phase channel technique. Specifically, the main effects related to random field modulation are considered. The nonmonotonic change of correlation radius along the pulse length is explained. The results obtained are in good agreement with data of laboratory and numerical experiments.Moscow State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 34, No. 2, pp. 136–141, February, 1991.     

Nonparaxial vortex vector solitons in a nonlinear cubic medium

The propagation of narrow three-dimensional wave beams in a nonlinear cubic medium has been analyzed taking into account all vector components of the wave field, including radial, angular, and longitudinal ones. Soliton solutions to the Maxwell equations in the form of vortex solitons are found, and their properties are investigated.     

Subwavelength spatial solitons in inhomogeneous Kerr media

Propagation of a narrow beam in a periodic Kerr medium is analyzed for an arbitrary relation between the beam width, modulation period, and optical wavelength. Maxwell’s equations used to obtain solutions describing spatial optical solitons, and their basic properties are determined. The results are compared with those obtained by solving the paraxial nonlinear Schödinger equation. Conditions are found under which these models are mutually inconsistent.     

Eigenvalue control and switching by fission of multisoliton bound states in planar waveguides

We report the results of numerical studies of the fission of N-soliton bound states at the interface formed by a Kerr nonlinear medium and a linear dielectric in a planar waveguide. A variety of effects are shown to occur, with applications to all-optical eigenvalue soliton control.     

The nature of plateau on time-of-flight curves in molecularly doped polymers

Transient current curves in a polar molecularly doped polymer for surface and bulk generations of charge carriers are compared. No transformation of the horizontal plateau on the former to the curve predicted by the diffusion and drift theory was found, contrary to expectations for quasi-equilibrium transport conditions. This behavior indicates a nonequilibrium character of the transport of charge carriers. The plateau appearance is explained in our case by the depleted subsurface layer effect, as we already pointed out earlier.     

Mutual effects of temporal and spatial coherence of laser radiation during wind refraction

Conclusions Generalizing our results, one can identify the basic mechanism responsible for the mutual influence of temporal and spatial fluctuations in the amplitude of a light field in a moving medium with thermal nonlinearity.A necessary condition for this type of mutual interaction is a nonlinear incoherent effect connected nonlinearly with the induced fluctuations in the refractive index n_n. The mutual coupling of temporal and spatial variations is detectable only when the fluctuating part of n_n is comparable in magnitude to the normal refractive index, and when the distribution is nonuniform over the beam cross section and unstable during the pulse.The fundamental relationships of mutual interaction are that the slow fluctuations, which peel off the nonlinear medium over time, lead to a degradation of the spatial coherence of the light beam while it is being nonlinearly refracted. In all cases the spatial coherence of the laser radiation is reduced. The reverse effect of spatial fluctuations on the degradation of temporal coherence of a light pulse that is spatially-incoherent at the entrance to the medium is similar in its characteristics. This mutual interaction is substantially reduced when the nonstationary self-interaction regime promotes smoothing of fluctuations in the induced optical channel.Finally, we note that if the noise component of the pulse is a stable, uniform process, the transformations of the temporal and spatial coherence of a light field will occur independently in a nonlinear medium.Moscow State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 32, No. 7, pp. 816–822, July, 1989.     

Vibrational spectra of activated rei of wolframile-phosphate glasses

The vibrational spectra of wolframile-phosphate glasses with a high concentration of WO ₂ ²⁺ and Ln³⁺ ions were investigated and the structure of these glasses was analized. It is shown that the investigated glasses are formed predominantly by chain polyphosphates. Tungstate enters into the net of the glass in octahedral coordination, “stitching” the polyphosphate chains together but not isomorphously substituting phosphorus. In the glass structure nonlinear wolframile groups with the multiple tungsten-oxygen bonds are formed. The introduction of lanthanide oxides into the glass composition causes the average degree of its polymerization to decrease. F. Skorina Gomel' State University, 104 Sovetskaya St., Gomel', 246699, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 2, pp. 236–241, March–April, 1997.