Progress in observation of solitons in photonic topological insulators is discussed. Results are presented of experiments with nonlinear topological states in Su-SchriefferHeeger arrays fabricated using the femtosecond writing technique that are static, i.e., invariable in the direction of light propagation, and dynamically modulated (primarily periodically) in the direction of light propagation. Such objects are one of the simplest models of a topologically nontrivial structure. Solitons in topological insulators bifurcate with increasing laser beam power from linear edge states in the topological bandgap, inheriting their topological protection. The spatial localization of the soliton and the position of its propagation constant in the topological bandgap depend in a nonlinear medium on peak power and can be effectively controlled. Experimental observation of the switching of the edge topological modes in the bandgap between two closely spaced dimerized Su-Schrieffer-Heeger arrays is presented. The switching, whose rate depends on radiation intensity, can be completely arrested in a strongly nonlinear regime. In trimer waveguide arrays, whose spectrum in the topological phase features two simultaneously emerging topological bandgaps with edge states of different symmetries, two coexisting types of topological solitons exhibiting different degrees of stability were observed. We also discuss experimental observations of TE-solitons nonlinear topological Floquet states periodically reproducing their profiles in 1D- and 2D-dimensional Su-Schrieffer-Heeger arrays modulated in the direction of propagation of radiation.

We report low-loss multiscan waveguides fabricated in fused silica using femtosecond-laser-writing technology. The multiscan principle allows the writing regime to be tailored to excel at key features of any integrated photonic platform: coupling losses and propagation losses. We optimized the writing parameters for different sizes of square-shaped waveguides and reached the mode overlap value with a standard single- mode optical fiber of above 98.8% and demonstrated very low coupling losses of 0.2 dB/facet on average. Propagation losses in the fabricated waveguides amounted to 0.07 dB/cm. We applied the developed recipe to the fabrication of a fiber-coupled 25-channel interferometer with total insertion losses below 1 dB. The findings of this work are of interest for broad range of applications and in particular for optical information processing and quantum photonics.

The features of nonlinear propagation of high-intensity pulses in the short-wavelength infrared range in extended one-dimensional waveguide arrays with different spatial periods, formed in fused silica by laser writing, are studied. More than tenfold self-compression of femtosecond pulses up to a duration of several periods of the light field is experimentally observed.

We derive the area theorem for light pulses interacting with inhomogeneously broadened ensemble of two-level atoms in a single-mode optical waveguide and present its analytical solution for Gaussian-type modes, which demonstrates the significant difference from the formation of $2π$ pulses by plane waves. We generalize this theorem to the description of photon echo and apply it to the two-pulse (primary) echo and the revival of silenced echo (ROSE) protocol of photon echo quantum memory. For the first time, we implemented ROSE protocol in a single-mode laser-written waveguide made of an optically thin crystal $Tm^{3+}:Y_3Al_5O_{12}$. The experimental data obtained are satisfactorily explained by the developed theory. Finally, we discuss the obtained experimental results and possible applications of the derived pulse area approach.

In this work, optical spectroscopy of thulium ions in a single-mode optical waveguide fabricated in a Tm3+:Y3Al5O12 crystal using the femtosecond laser printing method was carried out and an optical quantum memory protocol was demonstrated in a revival of silenced echo scheme. An analysis of the experimental data indicates the presence of instantaneous spectral diffusion at a thulium ion concentration of less than 0.01%, a weak effect of imperfections in the formed waveguide on the lifetime of the optical memory, and indicates the possibility of achieving a high efficiency of input signal recovery in the implemented waveguide scheme of the protocol.

В настоящей работе был реализован протокол оптической квантовой памяти в схеме восстановления сигнала подавленного эха в одномодовой волноводной структуре, сформированной кристалле Tm3+:Y3Al5O12, актуальной для создания интегральной квантовой памяти в кристаллах, активированных редкоземельными ионами.

В настоящей работе был реализован протокол оптической квантовой памяти в схеме восстановления сигнала подавленного эха в одномодовой волноводной структуре, сформированной кристалле Tm3+:Y3Al5O12, актуальной для создания интегральной квантовой памяти в кристаллах, активированных редкоземельными ионами.

Reconfigurability of integrated photonic chips plays a key role in current experiments in the area of linear-optical quantum computing. We demonstrate a reconfigurable multiport interferometer implemented as a femtosecond laser-written integrated photonic device. The device includes a femtosecond laser-written $4\times 4$ multiport interferometer equipped with 12 thermooptical phase shifters, making it a universal programmable linear-optical circuit. We achieve a record fast switching time for a single nested Mach-Zender interferometer of $\sim10$ ms and quantitatively analyse the reconfigurability of the optical circuit. We believe, that our results will improve the current state of quantum optical experiments utilizing femtosecond laser-written photonic circuits.

We produced optical waveguides in the Er-167(3+) :(LiYF4)-Li-7 crystal with diameters ranging from 30 to 100 mu m by using the depressed-cladding approach with femtosecond laser. Stationary and coherent spectroscopy was performed on the 809 nm optical transitions between the hyperfine sublevels of I-4(15/2) and I-4(9/2) multiplets of Er-167(3+) ions both inside and outside of waveguides. It was found that the spectra of Er-167(3+) were slightly broadened and shifted inside the waveguides compared to the bulk crystal spectra. We managed to observe a two-pulse photon echo on this transition and determined phase relaxation times for each waveguide. The experimental results show that the created crystal waveguides doped by rare-earth ions can be used in optical quantum memory and integrated quantum schemes.

We present a study of optical quantum states generated by subtraction of photons from the thermal state. Some aspects of their photon number and quadrature distributions are discussed and checked experimentally. We demonstrate an original method of up to ten photon subtracted state preparation with use of just one single-photon detector. All the states where measured with use of balanced homodyne technique, and the corresponding density matrices where reconstructed. The fidelity between desired and reconstructed states exceeds 99%

Low-loss single-mode optical waveguide fabrication process in extra-white soda-lime glass is demonstrated. Waveguiding structures are formed in bulk substrates employing femtosecond laser writing technology. The combination of a slit beam shaping method and a multiscan fabrication process enables writing of waveguides with a well-defined symmetric cross-sectional profile. Fabricated waveguides exhibit 0.86 dB/cm propagation loss for 800-nm wavelength. Bending loss in the waveguides is addressed experimentally and compared with a model for radiation loss.

The problem of mathematical modeling of multiphase flow is closely linked with the problems of the development of oil and gas reservoirs. Big part of the world's oil reserves is located in fields with fracture-porous type collectors. Our presentation deals with mathematical modelling of the processes such reservoirs. This work presents some of the results obtained recently in the framework of the project, funded by the Russian Science Foundation. This is a whole complex computing tasks include, as a direct implementation of the model multiphase fluid flow in heterogeneous fractured porous media. in the presence of injection and production wells with access to the permafrost zone, and a number of auxiliary tasks: modeling of filtration gas combustion, the problem of constructing the new generation of efficient numerical algorithms. Here we present some results on incompressible fluid flow in heterogeneous fractured porous media. We deal with two approaches: direct description of cracks using detail meshes and double porosity models, based on G.I. Barenblatt’s approach (see, for example, G.I. Barenblatt, V.M. Entov, V.M. Ryzhik, 1984). In the last case we consider single phase and two-phase fluids separately. For two-phase fluid some new model of mass transfer between cracks and porous blocks is proposed.

We present a family of optical quantum states generated by subtraction of photons from the thermal state. The experimental realization of their preparation, measurement, and quantum state reconstruction is demonstrated. The proposed technique allows generation of up to 10-photon subtracted thermal states with the fidelity higher than 99%. Combined with homodyne detection it can also be used for precise measurement of high-order autocorrelation functions.

Interaction of magnesia-ferriferous slag ground in air and carbon dioxide atmosphere with alkaline solutions, has been studied. Experimental data on Si and Al dissolution extent from the slag treated by NaOH solution have been obtained, the+ dependence of this dissolution extent on the ball mill grinding time, grinding atmosphere and NaOH concentration has been investigated. It has been concluded that the surface of the slag particles mechanochemically carbonized by grinding in CO2 atmosphere exhibits enhanced reactivity and this fact is correlated with the rise of the compressive strength of geopolymers prepared from this slag. Experimental results are in a good agreement with the data of the thermodynamic modelling of the interaction between the slag and NaOH carried out using the “Selector” software.

Mechanically activated iron-ore concentrate (IOC) JSC «OLKON» has been studied as a component of special composite binding material with a large volume weight. Portland cement – IOC – water and IOC – gypsum –water compositions have been investigated. It has been concluded that it is possible to obtain material based on the mechanically activated iron-ore concentrate and gypsum (phosphogypsum) using pressing method. This material consists of 95-98% IOC and 5-2% gypsum and its compressive strength is ~10 MPa and volume weight is 3.8-3.9 g/cm3. This material can be used for production of the special facing tiles protecting from radiation.

Within the mixed finite element method the numerical model for two-phase incompressible fluid filtration is designed in the terms "velocity-pressure-saturation". The main difficulty of the model is caused by fractured porous medium. Our approach allows to resolve difficulties wtith boundary condition degeneration for the saturation.