Filamentation processes and dynamical excitation of light condensates in optical media with competing nonlinearities

We analyze both theoretically and by means of numerical simulations the phenomena of filamentation and dynamical formation of self-guided nonlinear waves in media featuring competing cubic and quintic nonlinearities. We provide a theoretical description of recent experiments in terms of a linear stability analysis supported with simulations, showing the possibility of experimental observation of the modulational instability suppression of intense light pulses travelling across such nonlinear media. We also show a novel mechanism of indirect excitation of {\em light condensates} by means of coalescence processes of nonlinear coherent structures produced by managed filamentation of high power laser beams.Comment: 6 pages, 4 figure

Intrinsic beam shaping mechanism in spatially modulated broad area semiconductor amplifiers

Postprint (published version

Characteristics of silent countingin synchronized swimmers

This article describes the temporal characteristics of silent counting as used duringa competition by the Russian youth team of synchronized swimmers. Theathletes listened to the music that accompanied their performance at the competition.Diff erent indices of silent counting were defi ned, such as the beginningand cessation of diff erent periods of counting, counting frequency, the stabilityof the temporal structure of silent counting, the degree of synchronization of silentcounting at diff erent moments during the sports program. We studied therelationship of these characteristics of counting with expert estimates of the athletes’sense of tempo, coordination of movements, and choreographic abilities

Modulational instability in nonlocal Kerr-type media with random parameters

Modulational instability of continuous waves in nonlocal focusing and defocusing Kerr media with stochastically varying diffraction (dispersion) and nonlinearity coefficients is studied both analytically and numerically. It is shown that nonlocality with the sign-definite Fourier images of the medium response functions suppresses considerably the growth rate peak and bandwidth of instability caused by stochasticity. Contrary, nonlocality can enhance modulational instability growth for a response function with negative-sign bands.Comment: 6 pages, 12 figures, revTeX, to appear in Phys. Rev.

Pattern generation by dissipative parametric instability

Nonlinear instabilities are responsible for spontaneous pattern formation in a vast number of natural and engineered systems, ranging from biology to galaxy buildup. We propose a new instability mechanism leading to pattern formation in spatially extended nonlinear systems, which is based on a periodic antiphase modulation of spectrally dependent losses arranged in a zigzag way: an effective filtering is imposed at symmetrically located wave numbers k and -k in alternating order. The properties of the dissipative parametric instability differ from the features of both key classical concepts of modulation instabilities, i.e., the Benjamin-Feir instability and the Faraday instabiltyity. We demonstrate how the dissipative parametric instability can lead to the formation of stable patterns in one- and two-dimensional systems. The proposed instability mechanism is generic and can naturally occur or can be implemented in various physical systems

Two dimensional modulational instability in photorefractive media

We study theoretically and experimentally the modulational instability of broad optical beams in photorefractive nonlinear media. We demonstrate the impact of the anisotropy of the nonlinearity on the growth rate of periodic perturbations. Our findings are confirmed by experimental measurements in a strontium barium niobate photorefractive crystal.Comment: 8 figure

Development of encapsulated extracts on the basis of meadowsweet (Filipendula ulmaria) in the composition of functional foods with oncoprotective properties

ArticleMeadowsweet (Filipendula ulmaria) is a quite common plant throughout the European countries, including Russia. Therapeutic and prophylactic properties of the meadowsweet are mainly associated with the action of biologically active substances (BAS), in particularly tannins, phenolic compounds, phenolcarboxylic acids, catechins, flavonoids, essential oils etc. The main substances with proven clinical effects are salicylates and flavonoids, what allows to consider meadowsweet as an anti-inflammatory, immunostimulating, antioxidant, hepatoprotective, nootropic, adaptogenic and antihypoxic agent. The aim of this study was to analyze the content of BAS in water and 70% ethyl alcohol extract of F. ulmaria flowers from different regions of Russia and develop their encapsulated forms for further use as an ingredient for functional food products. To increase the shelf life of meadowsweet extracts and create a stable form for their delivery to the human body with various food products, encapsulated forms of extracts in the form of microand nanosized capsules were developed. The method of encapsulation was carried out using a spray dryer. It was shown that encapsulated meadowsweet BAS can be added to a chicken pate without negative effect on the organoleptic properties of the finished product. The calculation of the cost of the meat product with the complex functional dry mixture showed a slight increase in the cost of the final product compared to the traditional analogue. This study shows that encapsulated meadowsweet BAS can be used for inclusion in various food products, to ensure the functional properties of food and optimize the population's rations

Modulational instability and nonlocality management in coupled NLS system

The modulational instability of two interacting waves in a nonlocal Kerr-type medium is considered analytically and numerically. For a generic choice of wave amplitudes, we give a complete description of stable/unstable regimes for zero group-velocity mismatch. It is shown that nonlocality suppresses considerably the growth rate and bandwidth of instability. For nonzero group-velocity mismatch we perform a geometrical analysis of a nonlocality management which can provide stability of waves otherwise unstable in a local medium.Comment: 15 pages, 12 figures, to be published in Physica Script

Laser beam filamentation in fractal aggregates

We investigate filamentation of a cw laser beam in soft matter such as colloidal suspensions and fractal gels. The process, driven by electrostriction, is strongly affected by material properties, which are taken into account via the static structure factor, and have impact on the statistics of the light filaments.Comment: 4 pages, 5 figures. Revised version with corrected figure 5. To be published in Phys. Rev. Let

Discrete instability in nonlinear lattices

The discrete multiscale analysis for boundary value problems in nonlinear discrete systems leads to a first order discrete modulational instability above a threshold amplitude for wave numbers beyond the zero of group velocity dispersion. Applied to the electrical lattice [Phys. Rev. E, 51 (1995) 6127 ], this acurately explains the experimental instability at wave numbers beyond 1.25 . The theory is also briefly discussed for sine-Gordon and Toda lattices.Comment: 1 figure, revtex, published: Phys. Rev. Lett. 83 (1999) 232