Britvin, Aleksandr Viktorovich

Britvin A.V., Konyaev S.I., Poller B.V., Poller A.B., Khairetdinov M.S.

The problem of measuring the spatiotemporal and energy parameters of acoustic infrasonic oscillations in the atmosphere is considered based on the placement of laser and fiber lines in geoecological monitoring zones. The measurements are based on the phenomenon of acousto-optical transformation at infralow frequencies associated with the influence of an external acoustic wave field on the characteristics of the propagation of laser pulse beams in this field. Background and anthropogenic atmospheric acoustic processes are used as external field sources. The measured parameter is the fluctuation of the phase (frequency) of the atmospheric optical signal relative to the reference optical fiber signal. The characteristics of the atmospheric fiber laser system and some results of experiments on assessing the statistics of fluctuations in the phase of atmospheric laser pulses and the parameters of infrasound fields in a given atmospheric monitoring zone are presented.

Britvin A.V., Nikitenko N.S., Shahov N.V., Poller B.V., Poller A.B.

Britvin A.V., Nikitenko N.S., Plyusnin V.F., Poller B.V., Poller A.B., Shakhov N.V.

We studied the photostability of planar-fiber structures in the form of films with a thickness of 600–800 µm under long-term ultraviolet irradiation. The films were made of highly pure polymethylmethacrylate (PMMA) and acrylic resin and doped with Coumarin 7, 47, and 120, POPOP, and NOL8 luminophores. Luminophore NOL12 (KNL12) was in polymer fibers produced by the Technological Center of Polymer Optical Fiber (Russia). PMMA optical fibers were attached to the ends of the films; the luminescence radiation power was measured from the output of these PMMA fibers as a function of the UV irradiation power and time. The prospects of using Coumarin-type luminophores in planar-fiber structures in UV information systems as receiving antennas for optical telecommunications and optical sensors for monitoring physical fields are demonstrated.

Khairetdinov M.S., Poller B.V., Borisov B.D., Britvin A.V.

Processes of acoustooptical interaction at infralow frequencies with the use of seismic vibrators as sources of low-frequency acoustic oscillations propagating in the atmosphere and laser measuring lines as optical receivers of oscillations are studied. The proposed types of the source and receiver in the interest of studying the acoustooptical interaction determine the novelty and originality of the proposed approach. Results of experiments on estimating characteristics of the acoustooptical interaction at infralow frequencies in problems of laser ecological monitoring of the environment are presented.

Khairetdinov M.S., Poller B.V., Britvin A.V., Sedukhina G.F., Mashnikov D.Y.

In this paper, the processes of acoustooptic interaction at infralow frequencies are studied usingseismic vibrators as sources of low-frequency acoustic oscillations propagating in the atmosphere and laser measurement lines as optical receivers of oscillations. The source and receiver types being proposed to investigate the acoustooptic interaction determine the novelty and originality of the approach. The results of experiments for estimating the characteristics of the acoustooptic interactionat infralow frequencies are presented.

Khairetdinov M.

Khairetdinov M.S., Poller B.V., Britvin A.V., Sedukhina G.F.

In this paper, an original approach to studying acoustooptic interactions at infralow frequencies using seismic vibrators is proposed. It has been proved by the authors in numerous natural experiments that such sources can radiate low-frequency acoustic oscillations propagating in the atmosphere up to hundreds of kilometers from the source. High-precision metrological properties of vibrators for force and frequency-time characteristics - open up new for investigating acoustooptic interactions at infralow frequencies. An acoustooptic system developed by the authors is described. The system consists of the CV-40 vibrator, an optical bench with a laser emitter with a radiation power of up to 6 W at a wavelength of 850-930 nm and a pulse repetition rate of 1 kHz, a set of acoustic measurement stations, and a meteorological station. The results of natural and test experiments on acoustooptic interactions are presented.

Trashkeev S.I., Britvin A.V.

The system of equations describing the thermal orientation effect in nonchiral liquid crystals, which was observed earlier, is proposed and substantiated. The effect of the director reorientation under the action of the temperature gradient is in many ways analogous to the Freedericksz transition in electric or magnetic fields. The angle of deviation of the director from the initial position is determined by the square of the temperature gradient. The effect is observed for a nematic liquid crystal, initially uniformly oriented, and is not accompanied by macroscopic fluxes of the medium under stationary conditions.

Britvin A.V., Konyaev S.I., Poller B.V., Poller A.B., Khairetdinov M.S.

The problem of measuring the spatiotemporal and energy parameters of acoustic infrasonic oscillations in the atmosphere is considered based on the placement of laser and fiber lines in geoecological monitoring zones. The measurements are based on the phenomenon of acousto-optical transformation at infralow frequencies associated with the influence of an external acoustic wave field on the characteristics of the propagation of laser pulse beams in this field. Background and anthropogenic atmospheric acoustic processes are used as external field sources. The measured parameter is the fluctuation of the phase (frequency) of the atmospheric optical signal relative to the reference optical fiber signal. The characteristics of the atmospheric fiber laser system and some results of experiments on assessing the statistics of fluctuations in the phase of atmospheric laser pulses and the parameters of infrasound fields in a given atmospheric monitoring zone are presented.

Britvin A.V., Nikitenko N.S., Shahov N.V., Poller B.V., Poller A.B.

Smolekho I.V., Sadovskaya O.V., Sadovskii V.M.

Dynamic processes in liquid crystals are investigated with the help of simplified mathematical model, describing mechanical, temperature and electrostatic perturbations. On the basis of these equations, the separate subsystem for angular velocity and tangential stress is deduced and analyzed. The problem of perturbing an extended liquid crystal layer by an electric field is considered. It is created by charges on the capacitor plates, periodically located along the layer. The right-hand sides of the second-order equations include bulk forces and moment of forces caused by the electric field action. An algorithm for numerical solution of the subsystem of equations is developed. At the first stage of this algorithm the bulk forces and moment of forces are calculated based on the equations of electrodynamics using the method of straight lines, and at the second stage the distributions of tangential stress, angular velocity and angle of rotation of the liquid crystal molecules are found using the finite-difference scheme “cross”. The algorithm is implemented as a parallel program written in C++ using CUDA technology for computing systems with graphics accelerators.

Shvetsov S.A., Zolot’ko A.S., Voronin G.A., Emelyanenko A.V., Statsenko P.A., Trashkeev S.I.

Abstract The effect of nonlinear light action on a thin (∼10 µm) films of the nematic liquid crystal deposited onto the absorbing substrate is experimentally investigated. The dynamics of the orientational and thermocapillary effects is directly studied. The two types of orientational processes were found out. The first one appears for several hundreds of milliseconds when the light beam irradiation is turned on or off. The second one develops much slowly and does not relax during the light beam irradiation.

Khairetdinov M., Shimanskaya G., Mikhailov A., Imomnazarov H.

The optimization problem of inter-wave transformations in adjacent geophysical media is considered in connection with the analysis of the phenomenon of acoustic-seismic conversion. It concerns the transformation of an atmospheric acoustic wave into a surface seismic wave. To characterize the transformation effect, a quantitative factor in the form of an energy criterion proposed. In this case, the problem of optimizing the inter-wave transformation is reduced to finding conditions that maximize criterion. There is a number of limiting factors that can neutralize the effect of acousto-seismic transformation. In as significantly weaken the effect for acoustic-seismic transformation screening effect of the snow cover in the article is discussed. Mathematical simulation of the elastic waves propagation from infralow frequency source taking into account snow cover is considered. The programs for calculation of the acoustic levels through mathematical model based on the conservation laws and differential equations for porous snow medium are implemented. The results of the processing and analysis of the experimental data taking into account the snow cover is executed.

Oswald P., Dequidt A., Poy G.

This chapter describes two crossed effects observed in nematic and cholesteric liquid crystals (LC) subjected to a temperature gradient G. The first effect couples the rotation of the molecules to the temperature gradient (thermomechanical [TM] effect), while the second one couples the flows to the temperature gradient (thermohydrodynamical effect). The chapter describes the Éber and Janossy experiment that revealed for the first time the existence of a TM effect in a cholesteric LC. It summarizes the main theoretical results obtained by Sarman and coworkers by molecular dynamics simulations in the case of the TM effect. The dynamic experiments are more spectacular because they show more directly the non-equilibrium TM effect. The chapter describes the experiments in which translationally invariant configurations (TIC) are set into continuous rotation by application of a temperature gradient. The comparative experiments with different types of TICs have nonetheless proven their existence and have allowed us to estimate their order of magnitude.

Shvetsov S.A., Zolot’ko A.S., Voronin G.A., Emelyanenko A.V., Avdeev M.M., Bugakov M.A., Statsenko P.A., Trashkeev S.I.

We report the light beam action on the nematic liquid crystal film with a free surface. It was found that a weak light absorption by the liquid crystal substrate dramatically changes the orienting properties of the light beam; in particular, a thermal gradient field induces an umbilical defect formation.

Khairetdinov M.S., Poller B.V., Borisov B.D., Britvin A.V.

Processes of acoustooptical interaction at infralow frequencies with the use of seismic vibrators as sources of low-frequency acoustic oscillations propagating in the atmosphere and laser measuring lines as optical receivers of oscillations are studied. The proposed types of the source and receiver in the interest of studying the acoustooptical interaction determine the novelty and originality of the proposed approach. Results of experiments on estimating characteristics of the acoustooptical interaction at infralow frequencies in problems of laser ecological monitoring of the environment are presented.

Trashkeev S.I., Vasenin N.T., Vatnik S.M., Vedin I.A., Ivanenko A.V., Klementyev V.M.

Trashkeev S.I., Nyushkov B.N., Shvetsov S.A.

In this study, the beam mode conversion in a nematic liquid crystal film deposited on the end-face of a single-mode optical fibre is considered. The infrared laser radiation delivered by this fibre induces a defect structure in the initially homeotropic liquid crystal. This leads to the formation of an output light beam with the annular intensity distribution in its cross-section. The obtained beam mode maintains its transverse profile in free space and can be interpreted as an optical vortex.

Nyushkov B.N., Trashkeev S.I., Ivanenko A.V., Kolker D.B., Purtov P.A.

Nonlinear optical coupling between two single-mode fibers terminated coaxially in a nematic liquid crystal (NLC) was explored for the first time. Light-induced reorientation of nematic molecules can result in the stable self-collimation of light transmitted through the gap between fibers. Thus, high coupling efficiency can be achieved despite large fiber spacing. We demonstrated a coupling efficiency of up to ~0.7, achieved with spacing equal to four diffraction lengths. This feature opens up possibilities for the development of novel in-line fiber-optic elements based on NLCs. For instance, a polarization controller was proposed and considered.

Hakobyan M.R., Alaverdyan R.B., Hakobyan R.S.

It is observed and theoretically and experimentally studied thermomechanical flow in hybrid and cylindrical-hybrid oriented nematic liquid crystals (NLCs). The latter corresponds to the cell with homeotropic and axial boundary conditions on the substrates. The thermomechanical flow and rotation of NLC in such cells proceeds due to vertical temperature gradient. We suggest an experimental set up, a new configuration of NLC, for testing one of the twelve relations between twelve thermomechanical coefficients. In order to check the remaining relations between those coefficients it is important to have various configurations of NLC possible via photoalignment technology.

Kim Y., Majumdar M., Senyuk B.I., Tortora L., Seltmann J., Lehmann M., Jákli A., Gleeson J.T., Lavrentovich O.D., Sprunt S.

Using a range of optical techniques, we have probed the nature of orientational order in a thermotropic bent-core liquid crystal, which features a shape-persistent molecular architecture designed to promote a biaxial nematic phase. In the upper range of the nematic phase (enantiotropic regime), dynamic light scattering reveals strong fluctuations attributable to the biaxial order parameter, in addition to the usual uniaxial director modes. Assuming a Landau-type expansion of the orientational free energy, we estimate the correlation length associated with these fluctuations to be ∼100 nm. At lower temperatures, and mainly in the monotropic regime of the nematic, we observe by optical conoscopy an apparently biaxial texture, which develops when the sample temperature is changed but then relaxes back to a uniaxial state over time scales much longer than observed in the light scattering measurements. A combination of fluorescence confocal polarizing microscopy and coherent anti-Stokes Raman scattering confirms that the conoscopic texture arises from a flow-induced reorientation of the molecules, associated with a large thermal expansion coefficient of the material, rather than from the spontaneous development of a macroscopic secondary optical axis. We discuss a model to account for the observed behavior at both high and low temperatures based on the temperature-dependent formation of nanoscale, biaxially ordered complexes among the bent-core molecules within a macroscopically uniaxial phase.

Bagayev S.N., Klementyev V.M., Nyushkov B.N., Pivtsov V.S., Trashkeev S.I.

We report the recent results of research focused on a new kind of soft matter – the liquid-crystal nanocomposites with controllable mechanical and nonlinear optical properties. These are promising media for implementation of ultra-compact photonic devices and efficient sources of coherent radiation in a wide spectral range. We overview the technology of preparation of nematic-liquid-crystal media saturated with disclination defects. The defects were formed in different ways: by embedding nanoparticles and molecular objects, by exposure to alpha-particle flux. The defect locations were controlled by applying an electric field. We also present and discuss the recently discovered features of nematic-liquid-crystal media: a thermal orientation effect leading to the fifth-order optical nonlinearity, enormous second-order susceptibility revealed by measurements, and structural changes upon exposure to laser radiation. We report on efficient generation of harmonics, sum and difference optical frequencies in nematic-liquid-crystal media. In addition, transformation of laser radiation spectra to spectral supercontinua, and filamentation of laser beams were also observed in nematic-liquid-crystal media. We conclude that most nonlinear optical effects result from changes of the orientational order in the examined nematic liquid crystals. These changes lead to the symmetry breaking and disclination appearances.

Chamani S., Dehgani R., Rostami A., Mirtagioglu H., Mirtaheri P.

Visible Light Communication (VLC) is an important emerging choice for high-speed wireless communication. In this perspective, light-emitting diodes as illuminators will be modulated to transmit data simultaneously. However, the receivers bring severe difficulties due to cost, response time, and sensitivity with a wide Field Of View (FOV). To avoid these problems, one approach is to apply a large area photodetector; however, this solution is slow and costly. Another method is to focus light on a fast photodetector by optical components, but the photodetector’s FOV decreases, resulting from the conservation of etendue. Another option is Luminescent Solar Concentrators (LSCs). This paper demonstrates a novel shape of LSC with advantages such as inexpensive, fast response time, small antenna area for VLC purposes with significant geometrical gain, FOV, and ultra-broad bandwidth. It does not require any complex tracking system and active pointing but, due to its tiny size, it can also be adapted in integrating and mobile devices. Numerical simulation is done using Monte-Carlo raytracing, and the results are demonstrated in the spectral domain. The optical efficiency of the proposed antenna is obtained at 1.058%, which is about 0.4% better than the efficiency levels reported in other works, and the geometric gain of the antenna is reported to be 44, which is significant.

Oh S., Lee Y., Yu M., Cho S., Javed S., Chun H.

Vehicle-to-vehicle communication based on visible light communication has gained much attention. This work proposes a smart license plate receiver incorporated with a fluorescent concentrator, enabling a fast vehicle-to-vehicle communication with a large field of view and high optical gain. Communication performance is experimentally analyzed using off-the-shelf light-emitting diode-based headlamps for low-latency direct line of sight channel. Additionally, a blue laser diode-based beam-steering and tracking system, through image processing of taillights with a steerable mirror, is investigated. Data rates of 54 Mbps from the headlamps and 532 Mbps from the beam-steering channel with ±25° are demonstrated. In addition, real-time video streaming through the beam-steering channel is presented.

Kang C.H., Alkhazragi O., Sinatra L., Alshaibani S., Wang Y., Li K., Kong M., Lutfullin M., Bakr O.M., Ng T.K., Ooi B.S.

The use of optical carrier frequencies will enable seamless data connection for future terrestrial and underwater internet uses and will resolve the technological gap faced by other communication modalities. However, several issues must be solved to propel this technological shift, which include the limitations in designing optical receivers with large detection areas, omnidirectionality, and high modulation bandwidth, mimicking antennas operating in the radio-frequency spectrum. To address this technological gap, herein, we demonstrate halide-perovskite-polymer–based scintillating fibers as a near-omnidirectional detection platform for several tens-to-hundreds of Mbit/s optical communication in both free space and underwater links. The incorporation of all-inorganic CsPbBr3 nanocrystals by engineering the nanocrystal concentration in an ultraviolet-curable polymer matrix ensures a high photoluminescence quantum yield, Mega-Hertz modulation bandwidth and Mbit/s data rate suitable to be used as a high-speed fibers-based receiver. The resultant perovskite polymer-based scintillating fibers offer flexibility in terms of shape and near-omnidirectional detection features. Such fiber properties also introduce a scalable detection area which can resolve the resistance-capacitance and angle-of-acceptance limits in planar-based detectors, which conventionally impose a trade-off between the modulation bandwidth, detection area, and angle of view. A high bit rate of 23 Mbit/s and 152.5 Mbit/s was achieved using an intensity-modulated laser for non-return-to-zero on-off-keying (NRZ-OOK) modulation scheme in free-space and quadrature amplitude modulation orthogonal frequency-division multiplexing (QAM-OFDM) modulation scheme in an underwater environment, respectively. Our near-omnidirectional optical-based antenna based on perovskite-polymer-based scintillating fibers sheds light on the immense possibilities of incorporating functional nanomaterials for empowering light-based terrestrial- and underwater-internet systems.

Britvin A.V., Nikitenko N.S., Plyusnin V.F., Poller B.V., Poller A.B., Shakhov N.V.

We studied the photostability of planar-fiber structures in the form of films with a thickness of 600–800 µm under long-term ultraviolet irradiation. The films were made of highly pure polymethylmethacrylate (PMMA) and acrylic resin and doped with Coumarin 7, 47, and 120, POPOP, and NOL8 luminophores. Luminophore NOL12 (KNL12) was in polymer fibers produced by the Technological Center of Polymer Optical Fiber (Russia). PMMA optical fibers were attached to the ends of the films; the luminescence radiation power was measured from the output of these PMMA fibers as a function of the UV irradiation power and time. The prospects of using Coumarin-type luminophores in planar-fiber structures in UV information systems as receiving antennas for optical telecommunications and optical sensors for monitoring physical fields are demonstrated.

Sait M., Trichili A., Alkhazragi O., Alshaibaini S., Ng T.K., Alouini M., Ooi B.S.

Extending the field-of-view (FoV) of underwater wireless optical communication (UWOC) receivers can significantly ease the need for active positioning and tracking mechanisms. Two bundle of scintillating fibers emitting at 430- and 488-nm were used to detect two independent signals from ultraviolet and visible laser sources. A zero-forcing approach to minimize inter-channel crosstalk was further implemented. A net aggregated UWOC data rate of 1 Gb/s was achieved using two wavelengths and a non-return-to-zero on-off keying scheme.

Wang Z., Zhang L., Li J., Wei Z., Dong Y., Wei G., Fu H.Y.

We proposed a MIMO-NOMA system using a fluorescent quantum dots concentrator with wide FOV of 60°. The record sum rate of 144 Mbps is reached for UV-to-visible light communication over 2-m distance.

Khairetdinov M.S., Poller B.V., Borisov B.D., Britvin A.V.

Processes of acoustooptical interaction at infralow frequencies with the use of seismic vibrators as sources of low-frequency acoustic oscillations propagating in the atmosphere and laser measuring lines as optical receivers of oscillations are studied. The proposed types of the source and receiver in the interest of studying the acoustooptical interaction determine the novelty and originality of the proposed approach. Results of experiments on estimating characteristics of the acoustooptical interaction at infralow frequencies in problems of laser ecological monitoring of the environment are presented.

Khairetdinov M.S., Kovalevsky V.V., Shimanskaya G.M., Sedukhina G.F., Yakimenko A.A.

The problem of studying the interaction of various geophysical (seismic, acoustic, meteorological) fields is considered in the context of prediction of geoecological risks generated by technogenic and natural phenomena. It is proved that meteorological -dependent processes of propagation of infrasound from explosions in the atmosphere can greatly enhance the ecological loading on the social and natural environments. Such a situation is observed in regions of open strip mines, test sites, and other areas where regular explosions are made. Therefore the active vibrational method is proposed and investigated by the authors for the sounding of adjacent lithosphere–atmosphere media by strictly repeating small-power vibrational seismic and acoustic oscillations that powerful seismic vibrators can radiate. It is proved that simultaneous remote recording of both types of oscillations is possible. The use of the approach of active monitoring of the natural environment makes it possible to achieve ecological purity, high repeatability, and precision accuracy of the measurement parameters being estimated. The results of these works are illustrated by data from numerous experiments and numerical calculations.

Abramov M.L., Borisov B.D., Vasiliev V.A., Kuzyakin N.A.

Khairetdinov M.S., Poller B.V., Britvin A.V., Sedukhina G.F., Mashnikov D.Y.

In this paper, the processes of acoustooptic interaction at infralow frequencies are studied usingseismic vibrators as sources of low-frequency acoustic oscillations propagating in the atmosphere and laser measurement lines as optical receivers of oscillations. The source and receiver types being proposed to investigate the acoustooptic interaction determine the novelty and originality of the approach. The results of experiments for estimating the characteristics of the acoustooptic interactionat infralow frequencies are presented.

Odintsov S.L., Gladkikh V.A., Kamardin A.P., Mamyshev V.P., Nevzorova I.V.

The possibility of estimating the optical refractive index in the atmospheric boundary layer from air temperature profiles measured with a MTP-5 meteorological temperature profiler is studied. The refractive index profiles retrieved from MTP-5 data and from aerological measurements are compared. Examples of the refractive index and its derivatives for different seasons are given.

Mamyshev V.P., Odintsov S.L.

Results of the analysis of the “instantaneous” phase of narrow-band acoustic signals during their propagation on short near-surface paths under the action of the wind field are presented. The division of the phase into the deterministic, quasi-deterministic (“local”), and random (“turbulent”) components is applied. Histograms of the turbulent component of the phase and result of approximating the histograms by the normal law of the probability distribution are considered. An empirical formula for the relation between the phase variance at different frequencies and variance of the wind velocity on the sound propagation path is derived and compared with theoretical formulas.

Peyronel T., Quirk K.J., Wang S.C., Tiecke T.G.

Free-space optical communication holds the promise of high-throughput wireless communication channels for long distances as well as for short-range indoor applications. To fully benefit from the high data rates enabled by optical carriers, the light needs to be efficiently collected onto a fast photodetector, which requires complex pointing and tracking systems. Here, we show that fluorescent materials can be used to increase the active area of a photodiode by orders of magnitude while maintaining its short response time and increasing its field of view. Using commercially available materials, we demonstrate a detector with an active area of 126 cm2 achieving data rates up to 2.1 Gbps at an eye-safe intensity. We demonstrate a detector geometry with omnidirectional sensitivity and discuss the need for new materials tailored for communication applications.

Manousiadis P.P., Rajbhandari S., Mulyawan R., Vithanage D.A., Chun H., Faulkner G., O’Brien D.C., Turnbull G.A., Collins S., Samuel I.D.

Visible light communications (VLC) is an important emerging field aiming to use optical communications to supplement Wi-Fi. This will greatly increase the available bandwidth so that demands for ever-higher data rates can be met. In this vision, solid-state lighting will provide illumination while being modulated to transmit data. An important obstacle to realizing this vision are receivers, which need to be inexpensive, sensitive, fast, and have a large field of view (FoV). One approach to increasing the sensitivity of a VLC receiver is to increase the area of the receiver’s photodetector, but this makes them expensive and slow. An alternative approach is to use optical elements to concentrate light, but conservation of étendue in these elements limits their FoV. In this paper, we demonstrate novel antennas that overcome these limitations, giving fast receivers with large collection areas and large FoV. Our results exceed the limit of étendue, giving an enhancement of light collection by a factor of 12, with FoV semi-angle of 60°, and we show a threefold increase in data rate.

Zvanovec S., Chvojka P., Haigh P.A., Ghassemlooy Z.