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- Front Matter: Volume 10176
- APCOM16 Proceedings
Front Matter: Volume 10176
Front Matter: Volume 10176
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This PDF file contains the front matter associated with SPIE Proceedings Volume 10176, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.
APCOM16 Proceedings
Excitons and low-threshold optical nonlinearity of dielectric nanosystems
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The recently discovered ultralow-threshold nonlinear refraction of low-intensity laser radiation in dielectric nanostructures has an atypical dependence on radiation intensity. We first carry out quantitative measurements of the dependence of the nonlinear response of liquid dielectric nanostructures on the low-intensity radiation and then devise a theoretical explanation. The theory suggests that the nonlinearity is of photoinduced nature instead of a thermal one and depends directly on the nanoparticles electronic structure and the relationship between permittivities of dielectric matrix and nanoparticles.
Optical absorption by excitons of quasi-zero dielectric quantum dot
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As a part of the dipole approximation we study the interband optical absorption by nanosystem containing quantum dots (QD) alumina in a dielectric matrix. It is shown that the absorption edge of nanosystem mainly formed by two comparable in intensity electron transitions from low excited size quantized hole states on the ground size quantized electron state.
Mg2SixSn1-xheterostructures on Si(111) substrate for optoelectronics and thermoelectronics
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Thin (50-90 m) non-doped and doped (by Al atoms) Mg2Sn0.6Si0.4 and Mg2Sn0.4Si0.6films with roughness of 1.9-3.7 nm have been grown by multiple deposition and single annealing at 150 °C of multilayers formed by repetition deposition of three-layers (Si-Sn-Mg) on Si(111) p-type wafers with 45 Ω-cm resistivity. Transmission electron microscopy has shown that the first forming layer is an epitaxial layer of hex-Mg2Sn(300) on Si(111) substrate with thickness not more than 5-7 nm. Epitaxial relationships:hex-Mg2Sn(300)|| Si(111), hex-Mg2Sn[001]|| Si[-112] and hex-Mg2Sn[030]||Si[110] have been found for the epitaxial layer. But inclusions of cub-Mg2Si were also observed inside hex-Mg2Sn layer. It was found that the remaining part of the film thickness is in amorphous state and has a layered distribution of major elements: Mg, Sn and Mg without exact chemical composition. It was established by optical spectroscopy data that both type films are semiconductor with undispersed region lower 0.18 eV with no= 3.59 ± 0.01, but only two direct interband transitions with energies 0.75-0.76 eV and 1.2 eV have been determined. The last interband transition has been confirmed by photoreflectance data at room temperature. Fourier transmittance spectroscopy and Raman spectroscopy data have established the formation of stannide, silicide and ternary compositions.
Formation of bistable medium state in nanofluids under the influence of laser radiation
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We study the theory of the dynamics of the concentration of nanoparticles in a liquid-phase environment under the influence of a light field. An exact solution for the nonlinear diffusion equation was found in the form of switching waves. It is shown that under the conditions of a stationary and nonlinear temperature coefficient of thermal conductivity in the medium, nanofluids become bistable. A comparative analysis of linear and non-linear approaches to solving the diffusion equation is given.
Ultraviolet and EELS spectra of CeO2 nanoparticles produced by laser ablation
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The nanoparticles of cerium dioxide have been produced by laser ablation. The ultraviolet (UV) absorption spectra of the synthesized nanoparticles are studied. The band gap of the particles and the effect exerted on it by laser radiation intensity during the synthesis of nanoparticles are determined from the analysis of the spectra. Electron energy loss spectra (EELS) of the nanoparticles are investigated on a transmission electron microscope. Comparative analysis of the UV and EELS spectra has been carried out.
Light induced lens response in nanosuspension
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Thermal lens technique is widely used for the optical diagnostics of materials. The light-induced thermal lens in a homogeneous fluid is formed as a result of thermal expansion of a medium. In two-component fluid the heat flow also can cause concentration stream arising from occurrence of thermodiffusion (Soret effect). Another mechanism of optical nonlinearity of the medium is due to the forces operating on the particles of the dispersed phase in gradient light field. This paper analyzed the two-dimensional diffusion in the nanosuspension with two nonlinearities in a Gaussian beam radiation field. The light induced lens response is analyzed in the two-beam scheme when the reference and signal beams are of different wavelengths. As a result of the exact analytical solution of the problem the expression for the twocomponent medium lens response is achieved. The results are relevant to optical diagnostics of dispersed liquid materials, including the thermo-optical spectroscopy.
Optical methods in diagnostics of liver fibrosis via blood observation
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A possible application of optical methods (dielectrophoresis, spectral and imaging ellipsometry, Fourier- transform infrared spectroscopy, Raman spectroscopy) for the early diagnostics in studies of red blood cells and serum in patients with the diffuse liver disease, with varying degrees of fibrosis, has been evaluated. As experimentally confirmed, the combined optical methods significantly improve the sensitivity, specificity and accuracy index in the diagnosis of both severe fibrosis and slight ulterior liver fibrosis. The identified optical methods diagnostic potential can be efficiently utilized in noninvasive screening evaluation of the stages of diffuse liver disease of various genesis.
Study on thin wideband applicator for detecting blood characteristics in human body
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Preventive care as well as early detection method and monitoring technique for diseases are highly attracted attention to increase quality of life. Noninvasive measurement method for blood characteristics in body is expected by patients with kidney dysfunction. Complex permittivity of blood is changed a few present at 6GHz. This change is caused by the change of water and albumin contents in blood. In this study, to detect blood characteristics in human body, experiments with phantom model has been performed using thin wideband applicator for examining microwave transmission up to 6GHz. The thin wideband applicator has advantages for detecting living body information in detail. The thin wideband applicator is designed based on Antipodal Vivaldi Antenna and is not required any balun and is very easy handling. Using developed Antipodal Vivaldi Antenna, transmission coefficient can be obtained as a function of thickness of phantom model with high sensitivity. Using this method, highly sensitive sensor for obtaining characteristics of blood in body can be developed.
Monte Carlo simulation of Raman confocal spectroscopy of beta-carotene solution
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In this work, we report on two different and very efficient approaches for modelling of Raman scattering in turbid media irradiated by laser light. Both approaches utilize the Monte-Carlo method to simulate the Raman scattering process and optimized for different application scenarios. We compare the efficiency of both approaches and experimental results for confocal Raman spectroscopy.
Crystallography method for protein solutions photomodification study
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A method for qualitative and quantitative monitoring of protein solutions structural change by means of crystallograms is discussed. It was experimentally shown that the laser irradiation causes a reduction in the cluster characteristic size of protein in the solution and the changes in the structure depend on the total radiation energy and on the wavelength.
Protein solution photomodification analysis by means of craquelure structures
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A craquelure structure of protein film as indicator of macromolecule state is discussing. Craquelure is a network of fine cracks or crackles on the surface of a painting, caused chiefly by shrinkage of paint film or varnish. The actions of laser radiation in the red and green spectral region on the protein film craquelure structure by the example of albumin are considering. It is experimentally shown that after drying the protein layer a craquelure pattern (variety of cracks in the layer) is formed with the parameters strongly modified by the laser action and depending on the time (energy density) of exposure. The threshold energy of laser action is defined; it does not depend on wavelength significantly.
Laser activation of a nutrient medium and antibiotic solutions and its estimation by of bacteria growth dynamics
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A laser photomodifacation of nutrient mediums and antibiotics results at the microbiological supervision of bacteria colonies growth are discussed. It is experimentally shown, that on the irradiated media there is a delay of bacterial colonies growth number. Influence of laser radiation on activity of an antibiotic also is experimentally studied. It is revealed, that laser photomodifacation increases antimicrobic activity of a preparation. The mechanism of biological solutions activation is connected with the phenomenon laser nanoclusterization. Parameters of bacteria growth bacteria growth dynamics allow to numerically estimate degree of laser activation of nutrient mediums and pharmaceutical preparations.
Local heating in biological body using wireless transmission power into small resonant devices driven by MRI
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MRI is applying an electromagnetic (EM) wave for imaging. In application of EM waves, the heating effect will be applicable such as hyperthermia for cancer treatment. This paper examines heating effects of the small resonant devices using Radio Frequency (RF) signal generated by MRI. A small resonant device which is inserted in the body absorbs RF power, and its temperature can be increased. By this method, better heating efficiency and higher transmission properties will be realized. With using a simulator, transmission properties from an RF coil of the MRI to the small resonant device including signal power density and the SAR pattern are evaluated. Transmission properties can be obtained as a parameter of winding number of solenoid coil. In addition, the small resonant device is made on a condition as same as simulation and performed the experiments and measured the temperature rise using an optical fiber thermometer. The experimental results agree well with the simulation. From the results, it is found that the small resonant device is applicable for heating in human body.
Numerical simulation studies for optical properties of biomaterials
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Biophotonics involves understanding how light interacts with biological matter, from molecules and cells, to tissues and even whole organisms. Light can be used to probe biomolecular events, such as gene expression and protein–protein interaction, with impressively high sensitivity and specificity. The spatial and temporal distribution of biochemical constituents can also be visualized with light and, thus, the corresponding physiological dynamics in living cells, tissues, and organisms in real time. Computer-based Monte Carlo (MC) models of light transport in turbid media take a different approach. In this paper, the optical and structural properties of biomaterials discussed. We explain the numerical simulationmethod used for studying the optical properties of biomaterials. Applications of the Monte-Carlo method in photodynamic therapy, skin tissue optics, and bioimaging described.
Efficiency of use endobronchial laser doppler-flowmetry in patients with chronic leukemia
E. A. Vanina,
V. V. Voitsekhovskiy,
Y. S. Landyshev,
et al.
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In this work indicatorsendobronchial microcirculation were investigated in patients with chronic myeloid leukemia (CML), chronic lymphocytic leukemia (CLL), multiple myeloma (MM), polycythemia vera (PV), idiopathic myelofibrosis (IMF). A diagnostic bronchoscopy was performed using fibreoptic «Olympus» (Japan).Endobronchial laser Doppler flowmetry was carried out on the laser analyzer capillary blood LAK-02 (Russia). Laser Doppler flowmetry indicators such as parameter of microcirculation, the oscillation amplitude in the endothelial, neurogenic, myogenic, cardiac and respiratory ranges were calculated by continuous the Wavelet transforms. Reduced cardiac and respiratory amplitudes in CML and CLL are primarily due to the development leukostasis. If PV is the case, this is due to sludge syndrome. And when MM occurs, it is caused by protein stasis in the vessels of the bronchial tubes. Increased endothelial oscillation amplitudes in the range in CML, PV, IMF and their reduction in MM indicate the presence of endothelial dysfunction in these patients. Increasing the amplitude of oscillations in the range of neurogenic indicates the development of arteriolar vasodilation as a compensatory response to the violation of blood flow. Increasing the amplitude of oscillations of myogenic tone indicating decrease precapillaries as a compensatory reaction to improve blood flow. It is concluded that endobronchial laser Doppler flowmetry is an important method allowing diagnosing the pathology of the microvasculature of the bronchi in chronic leukemia.
A database of biominerals with optical properties founded in living organisms
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The living organisms – animals, plants, algae, fungi – contain miсroscopic inorganic inclusions (biominerals). A rather large body of information about their chemical composition, morphological types and presence in various parts of the organisms has been accumulated. Research in biominerals has a fundamental scientific value and can also be useful for development of materials with specific properties. We propose a database intended to comprise data about all known biominerals as an efficient practical tool for both fundamental biological research and development of biotechnology.
Formation of the reflected and refracted s-polarized electromagnetic waves in the Fresnel problem for the boundary vacuum-metamaterial from the viewpoint of molecular optics
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The refraction of a plane s-polarized electromagnetic wave on the vacuum–metamaterial interface is considered. Point particles with electric and magnetic dipole polarizabilities are scattering elements of a medium. The medium consists of plane-parallel monolayers of electric or magnetic dipoles or Huygens elements influencing one another. Dipole fields are completely taken into account. The fields inside the medium and the reflected fields are calculated. The extinction theorem is analyzed in detail. The mechanism of rotation of the magnetic field vector during refraction is elucidated. A reason for the absence of the fourth wave propagating from the medium toward the boundary in the conventionally employed boundary conditions is elucidated. It is shown that, under certain conditions, this medium can behave as possessing a unity refractive index or zero refractive index at a preset frequency. In the case of a metamaterial layer of finite thickness shows the output region of the existence of backward waves outside metamaterial layer. It is shown that the refraction of the field in a homogeneous medium after the dielectric corresponds to Fermat’s principle, and the interference nature of Fermat’s principle is justified.
Experimental verification of surface plasmon resonance excitation in bent single-mode optical fibers using whispering gallery modes
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We present an experimental verification of the novel approach to the excitation of surface plasmon resonance (SPR) for biosensing applications. The technique is based on a bent SMF28–type single-mode optical fiber with a thin metal film deposited on its optical cladding. Due to the bending of the fiber, strong coupling can be achieved between the fundamental mode and the surface plasmon mode through the intermediary of whispering gallery modes supported by the fiber cladding, which brings about a resonant dip in the transmission spectrum of the fiber. Since the propagation constant of the surface plasmon mode depends strongly on the refractive index of the surrounding medium so does the coupling wavelength, which enables precision refractometry both in the wavelength and intensity-modulated regimes. As opposed to traditional optical fiber-based SPR refractometers, our approach, while based on a standard single-mode fiber, needs neither additional optical elements (such as long-period or tilted Bragg gratings, etc.) nor mechanical modification of the fiber (such as chemical or mechanical removal of a part of optical cladding). This makes the proposed refractometer structurally simple, reliable, and easy to fabricate.
Numeric simulation of RF modulated optical pulses propagation in photonic time-stretch system
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This paper is dedicated to mathematical modelling of microwave signal processing by photonic time-stretch system. Photonic time-stretch system consists of wideband laser source, electro-optic modulator, two parts of optical fiber, photodiode and electronic ADC. Laser radiation is chirped in fiber, and then modulated by radio signal, which after that is stretched in fiber. Being stretched by second fiber module a pulse is send to photodiode, which converts a light intensity to electronic signal to be processed by ADC. Examples of simulation results are presented.
Hollow core Bragg fiber with antiresonant intermediate layer
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By means of the transfer matrix method, the optical properties of fibers with a distinct intermediate layer between a hollow core and periodic cladding are calculated. The periodic cladding consists of two types of the alternating layers. The intermediate layer has distinct thickness and refractive index. Depending on these parameters, the fiber can work in the single-mode or multi-mode regimes. In the multi-mode regime, the optical loss of the smallest loss mode can be decreased by increasing the thickness of the layer. In the single-mode regime, the optical loss falls with a rise in the refractive index of the intermediate layer. The optical properties of the fiber are determined by the antiresonance reflection from the intermediate layer and the Bragg reflection from the periodic cladding. Selecting the parameters of the intermediate layer, the optical loss of the fiber in the single-mode regime can be reduced by an order of magnitude over the loss of the traditional Bragg fiber.
Hydrothermal Synthesis of TiO2/WO3 Compositions And Their Photocatalytic Activity
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Photocatalytic activity, optical properties, thermal stability, phase patterns and morphology of nano-size ТiО2/WO3 compositions obtained from organic precursors through hydrothermal synthesis have been studied. It has been shown that doping of anatase nanoparticles with tungsten W+6 results in particle diameter reduction from 35 to 10 nm; decrease in width of the band gap from 3.15 eV to 2.91 eV and increase in temperature of phase transition of anatase to rutile up to 980оС. Catalytic activity of ТiО2/WO3 (4 mol.%) composition under photochemical methylene blue (MB) oxidation by simulated solar light exceeds that of undoped anatase (obtained in the same way) 6-fold.
Complex research of the particles which cause air pollution by laser granulometry, Raman-spectrometry and IR-spectrometry
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Applied monitoring studies of air pollution are often based on the use of time-tested, but not the most modern methods. The experience of the use of a complex method of atmospheric particle suspensions research, including laser granulometry, high-resolution mass spectrometry, light microscopy with Raman spectroscopy and scanning electron microscopy with energy dispersion analysis in hygienics and environmental research is discussed in the paper.
Formation of surface plasmon polaritons by silver nano-strip and nano-circle
Elena S. Kozlova,
Victor V. Kotlyar
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In this work the "central" surface plasmon-polariton was obtained by using frequency dependent finite difference timedomain method for the TM-polarized light at 532 nm, which was propagating through the silver nano-strip, placed in an aqueous medium. The height and width of nano-strip was equal to 20 nm and 215 nm respectively. The intensity of surface plasmon-polariton was four times higher the intensity of the incident radiation. The full width at half maximum of the nanojet was 138 nm. The "central" surface plasmon-polariton was obtained by using frequency dependent finite difference time-domain method for the radial-polarized light at 532 nm, which was propagating through the silver nanocircle, placed on a silica glass in an aqueous medium. The height and width of nano-strip was also equal to 20 nm and 215 nm respectively. The intensity of surface plasmon-polariton was four times higher the intensity of the incident radiation. The full width at half maximum of the nanojet was 158 nm. The results can be used to design devices that allow capturing and moving the particles in water or other biofluidics.
Simulation of internal charge distribution and spatial charge characteristics of ferroelectrics irradiated by focused electron beam
Anna V. Pavelchuk,
Anna G. Maslovskaya
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This article reveals the problem of electron transport as well as charging effect analysis in ferroelectrics subjected to electron beam irradiation at diagnostics with scanning electron microscope (SEM) techniques. The parameters of the electron irradiation doze and source function were estimated by means of 3D-Monte-Carlo simulation of electron trajectories in the solid specimen. The computation data were demonstrated for typical ferroelectrics irradiated by intermediate-energy electron bunches (10-40 keV). The modification of reaction-diffusion model was also presented to evaluate the electron beam-induced charging dynamics in ferroelectrics. The simulation was based on the joint numerical solution of the continuity equation and Poisson equation taking into account the intrinsic radiation-induced diffusion processes. The findings from this study enable demonstrating charge distribution, dynamics of the potential distribution, electric field components and electron beam-induced component of polarization at assigned parameters relative to experimental condition of reversal process of domain structure in electron beam-irradiated ferroelectrics.
Interaction of moving domain walls with constant magnetic fields in iron borate and yttrium orthoferrite single crystals
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The present paper deals with the experimental investigation of domain wall dynamics in iron borate and yttrium orthoferrite single crystals with an external magnetic field oriented perpendicularly to the magnetic momentum. Domain walls’ motion was caused by an alternating magnetic field, which was generated by the coils. For iron borate crystal we additionally considered the case, when the domain wall oscillation is caused by flexural vibration of the sample.
New data about optic properties of biominerals from some brown algae Undaria pinnatifida and Laminaria japonica
I. E. Pamirsky,
G. Chung,
S. A. Gutnikov,
et al.
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For the first time we made an attempt to study morphological types of phytoliths in the same species of multicellular brown algae (Undaria pinnatifida, Laminaria japonica) growing in different locations. However, in all samples only shapeless silicon dioxide particles were found. Some of them had rough edges, the other had smooth edges. We assume that the rough-edged shapeless phytolithes were formed within cells and smooth-edged – in the intercellular space. Verification of this assumption needs confirmation by detection of similar structures in the tissues of live algae.
Laser generation of ultrasound and ultrasound velocity measurements in glasses
P. V. Bazylev,
I. Ya. Krumgolts,
V. A. Lugovoy
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Laser generation of longitudinal ultrasonic waves in the quartz glass without of the sputtered absorbing metal layer is experimentally studied. For exaltation of ultrasound, the Q-switched solid-state laser having of laser-pulse duration 25 nanoseconds is used. Registration of ultrasound performed by non-contact broadband receiver – the laser interferometer that have of frequency range 0.5 – 80 MHz. Installation for precision measurements of ultrasonic waves velocity in solids on the basis of non-contact optical methods of excitation and reception of ultrasound is presented. Results of measurements of velocity of longitudinal ultrasonic waves in samples made of quartz glass with the thickness 1.5 – 100 mm are given. The expanded uncertainty of measurements makes 0.01 – 0.5 %.
Measurement of an ambient air leak by diode laser absorption spectroscopy
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Absorption spectroscopy measurements of long-lived metastable argon atoms Ar* in a low-pressure RF-discharge were carried out to measure gas leaks in a vacuum chamber. Argon as a carrier gas was flowing through the test chamber and the discharge cell at a rate of 55 μmol/s. If a leak occurs, the ambient air is admixed to the carrier gas flowing through the test chamber. The presence of air in the carrier gas flowing through the discharge plasma produced a decrease in the number density of Ar*, which was measured by means of diode laser absorption spectroscopy. This is because the lifetime of atoms is limited by losses due to collisions with air molecules. The leak-rate of the ambient air ranged from 0.14 to 0.95 μmol/s was measured by a mass flow meter and compared with the amplitude of the absorption signal.
Accelerating space-charge gratings in wide-bandgap semiconductors as a tool for simultaneous velocity and acceleration measurement
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We study the excitation of the two-wave mixing and non-steady-state photoelectromotive force signals using uniformly accelerated motion of the recording light pattern. Such illumination is created by the linear frequency modulation of the interfering light beams. The pulse response is predicted theoretically and observed experimentally in Bi12TiO20 and GaAs crystals at λ=633 nm. We analyse both the diffusion and space-charge wave regimes of signal excitation. The evolution of the pulse shape versus the chirp rate is demonstrated and explained in the frames of the developed theory. The application of the effects in laser Doppler velocimeters and accelerometers is discussed as well.
Diagnostics of nanosuspension by the light-induced pseudo-prism method
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Nonlinear optical techniques are widely used for the optical diagnostics of materials. The thermo-induced pseudo-prism method is used to study of the two-component materials. It is measured the angle of the light beam in the material with the thermo-induced refractive index gradient. This paper proposes a way to create pseudo-prisms in the nanodispersive liquid through the light radiation pressure. In the dispersed environment there is a specific mechanism of optical nonlinearity based on the redistribution of the dispersed particle concentration in the light field. The theoretical analysis of the light induced mass transport task was executed in the dispersed medium in a homogeneous light field. As a result of the analytical solution of the light induced mass transport task it was obtained an expression for the deflection angle of the beam in a pseudo-prism. The results are relevant in the study of the dispersed liquid media, as well as optical diagnostics of such materials.
Fiber-optic seismometers for weak seismic signals registration
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The vertical and horizontal seismometers based on fiber-optic Mach-Zehnder interferometer are proposed and tested. The sensing element of seismometers is implemented as a multiturn optical fiber coil which allowed to obtain for vertical seismometer sensitivity to acceleration 10–7 m/s2 and for horizontal seismometer sensitivity to displacement 10-9 m . Stability of the seismometer operation is provided by feed-back control of the interferometer working point. The possibility of registration of weak seismic signals are demonstrated.
Novel UV probe for selective detection of Au and Pd in aqueous solutions
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A novel turn on/off rhodamine 6G based fluorescent probe has been developed for selective detection of Au and Pd complexes in aqueous acidic solutions utilizing rhodamine spirolactam ring-opening process. Rhodamine derivatives have been widely used as versatile platforms for fluorescent probes. The newly designed probe reacts with [AuCl4]- and [PdCl4]2- to generate a product that has distinctly different optical properties. The probe undergoes a remarkable change in its absorption and emission spectrum upon addition of Au and Pd complexes that is associated with a discoloration and quenching of probe fluorescence. The probe exhibits near linear signal response and allows determination of Au and Pd content in aqueous solutions from 0.1 μM.
Dynamic measurement of temperature dependent permittivity and permeability by microwave irradiation
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To measure the temperature dependent complex permittivity and permeability of materials, measuring systems using cavity resonator in the frequency band of 2.45 GHz have been developed. To measure low loss material with wide temperature range, TE103 mode cavity resonator system excited by magnetron as power source has been applied. To measure higher loss material with high accuracy, TM010 mode cavity resonator system excited by solid state power source with vector network analyzer has been applied. By measuring transmission or reflection coefficient of the cavity with measuring the temperature using infrared thermograph, the temperature depending complex permittivity and permeability can be obtained. By using the developed systems, temperature dependent permittivity and permeability for metallic powders and ceramics have been measured and the results are shown in this paper.
A testing method for the machine details state by means of the speckle image parameters analysis
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Non destructive testing method, allowing defining a residual resource of power details of mechanical engineering designs under the analysis of registered speckle-image parameters, it is discussed. The "chessboard" algorithm based on calculation of correlation between the given speckle-image and a chessboard image is considered. Experimental research results of an offered non destructive testing method are presented. It is established, that to increase in quantity of a power detail tests cycles there is an increase in roughness parameters that conducts to reduction of correlation factor between reference and to resultants the image at the given stage of test. Knowing of correlation factor change dynamics, it is possible to define a residual resource of power details while in exploitation.
Luminescent chemosensors for amines and ammonia based on Eu(III) chelate complexes
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Here we report a novel luminescent sensor for amines and ammonia based on Eu(III) tris-β-benzoylacetonate complexes obtained in various conditions. It has been revealed that interaction of Eu(III) tris-β-benzoylacetonate with analyte vapor results in increase of the Eu(III) luminescence intensity. Exposure of Eu(III) complexes to ammonia and methylamine vapors results in a rapid increase of the emission and excitation spectra intensity and a rapid recovery, almost to the initial value, when the sample is exposed to air. Moreover, luminescence decay time value of Eu(III) complexes is in dependence on analyte presence and increase in ammonia atmosphere and decrease under purging of pure air. The dependences of sensor response features upon preparation conditions were shown. The mechanism of the analyte vapors effect on Eu(III) luminescence intensification has been suggested using the data of IR spectroscopy and quantum chemistry calculations. The mechanism of luminescence sensitization consists in bonding of an analyte molecule with a water molecule into the coordination sphere of Eu(III). As a result, the bond of a water molecule with the luminescence center weakens and the blockage of the quenching of luminescence on OH-vibrations takes place. The obtained data can be used for development of sensor materials with selective optical sensitivity to ecologically harmful vapours of organic and inorganic compounds.
The laser radiation action on the crystal formation processes in the biological fluids
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The results of an experimental study of the laser radiation effect on the crystal`s formation in the volume of biological fluids that are complex multi-component solutions have been discussing. Are investigated white and natural bile in vitro. The qualitative changes were observed. Thus, at the bottom of the cell in which bile is not exposed to the laser radiation, the crystals are formed. In the irradiated bile gallstone has a thin layer of a homogeneous viscous colloidal liquid with very small, visible in polarized light crystalline formations was got. Irradiated laser bile’s gallstone was covered evenly white deposit without surface defect unlike gallstone in bile without radiation exposure. A possible mechanism to explain the laser radiation action on the mineral formation in biological fluids and also practical application of this effect have been suggesting too.
Detecting weak acoustic fields by multichannel fiber-optical sensory system
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We present the multichannel fiber-optical system for detection and reconstruction of weak acoustic field. Developed system is based on 32-channel adaptive holographic interferometer that employs multiplexing of dynamic holograms in a single photorefractive crystal of CdTe. The multichannel fiber-optical sensory system was tested for registration and spatial reconstruction of acoustic field created in a solid plate.
Detection of acoustic emission signals in the polymer composite material by adaptive fiber-optic sensors
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The paper presents the results of an analysis of the acoustic emission signals recorded both by piezoelectric and adaptive fiber-optical sensors. Fiber-optical sensors have been embedded into the polymer composite material during their manufacture. Fiber-optical sensors are designed on the base of adaptive interferometer that uses a dynamic hologram formed in the photorefractive crystal. It has been shown that the sensitivity of adaptive interferometer allows the detection of acoustic emission signals generated by the Hsu-Nielsen source. Peculiarities of material sound velocity determination with use of acoustic signals detected by distributed fiber-optical sensors are discussed.
Fiber-optic hydrophone based on adaptive holographic interferometer
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In this paper, we developed and investigated an adaptive fiber-optic hydrophone based on adaptive holographic interferometer which key element is dynamic hologram recorded in a photorefractive crystal of cubic symmetry in orthogonal geometry. Different modifications of primary fiber-optic receivers of acoustic pressure are designed and studied. The adaptive hydrophone provides high sensitivity to acoustic pressure (up to 8.6 mV/Pa) and high level of immunity to all kind of noisy instabilities of environment.
Aerosol retrievals with multi-wavelength Raman lidar at IACP Lidar station
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LiDAR is effective tool for environment monitoring especially when for express analysis of atmosphere constituents such as aerosols, gas mixtures etc. Multi-wavelength raman lidar of IACP FEB RAS operates on thee wavelength Nd:YAG laser allows retrieving full set of optical and microphysical properties of atmosphere aerosols. This paper presents the results of using our lidar to retrieve atmospheric aerosol parameters in the vicinity of Vladivostok.
Highly sensitive two-channel laser acoustic sensor
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In this work, we present two-channel system for detecting acoustic waves which is based on adaptive holographic interferometer using multi-wave mixing in photorefractive crystal. Micromechanical silicon cantilevers with dimensions of 233×45×4 μm3 mounted on metal membrane are used as sensitive elements. For the first cantilever the detection threshold of acoustic pressure of the sensor on frequency of 6.9 kHz is 17 mPa. For the second cantilever the detection threshold of acoustic pressure of the sensor on frequency of 8 kHz is 49 mPa.
High spatial resolution absorption contrast imaging with electron-beam excitation assisted optical microscope
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We present high spatial-resolution label-free imaging with an electron-beam excitation-assisted optical microscope (EXA microscope). The EXA microscope improves the spatial resolution down to 100 nm. To realize the high spatial resolution, a nanoscale optical spot is generated by irradiating a fluorescent thin film with a focused electron beam whose spot size is less than 10 nm. The size of the optical spot becomes smaller than the diffraction limited spot size and is reduced to about 100 nm, because the light emission is localized in nanometer-sized region. In this microscopy, it is not necessary to label a specimen for imaging beyond the diffraction limit of the light. The specimen stage is separated from the vacuum chamber of the scanning electron microscope by the fluorescent thin film and a specimen under atmospheric pressure can be imaged.
We demonstrated that the high spatial resolution absorption contrast imaging of the crystal of vitamin B9 having absorption at UV wavelengths. The absorption wavelength matches with the wavelength of the emission of the fluorescent thin film we deposited. The fine crystal structure was imaged beyond the optical diffraction limit. The image contrast corresponded with the thickness of the crystal measured with an atomic force microscope (AFM). The illumination light is absorbed with the vitamin B9 crystal and the intensity of the transmitted light depends on the thickness of the vitamin B9 crystal. The EXA microscope is useful for analysis of growth of a crystal, bio-imaging, and so on.
Photonic sampled ADC’s: state of the art
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In this paper contemporary advances in analog-to-digital conversion based on photonic sampling are reviewed. Basic method of optical sampling and main types and realizations variants of photonic sampled ADC’s is briefly described. Some practical aspects of development of photonic ADC’s are shown. Limitations, modern level and possible progress in photonic sampled ADC’s is discussed.
Optical encryption of digital data in form of quick response code using spatially incoherent illumination
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Applications of optical methods for encryption purposes have been attracting interest of researchers for decades. The most popular are coherent techniques such as double random phase encoding. Its main advantage is high security due to transformation of spectrum of image to be encrypted into white spectrum via use of first phase random mask which allows for encrypted images with white spectra. Downsides are necessity of using holographic registration scheme and speckle noise occurring due to coherent illumination. Elimination of these disadvantages is possible via usage of incoherent illumination. In this case, phase registration no longer matters, which means that there is no need for holographic setup, and speckle noise is gone. Recently, encryption of digital information in form of binary images has become quite popular. Advantages of using quick response (QR) code in capacity of data container for optical encryption include: 1) any data represented as QR code will have close to white (excluding zero spatial frequency) Fourier spectrum which have good overlapping with encryption key spectrum; 2) built-in algorithm for image scale and orientation correction which simplifies decoding of decrypted QR codes; 3) embedded error correction code allows for successful decryption of information even in case of partial corruption of decrypted image. Optical encryption of digital data in form QR codes using spatially incoherent illumination was experimentally implemented. Two liquid crystal spatial light modulators were used in experimental setup for QR code and encrypting kinoform imaging respectively. Decryption was conducted digitally. Successful decryption of encrypted QR codes is demonstrated.
Object recognition in non-coherent optical correlator based on DMD-modulator
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There are many implementations of optical correlators based on LCD-SLM of different types currently available. Another kind of SLM, DMD-SLM, also is of great interest for use in optical correlators. The main advantage of this type of SLM relative to LCD-SLM is its very high operation speed. We developed and implemented the setup of optical correlator in which an input object is illuminated by spatially incoherent light and the filter-memory is dynamically displayed on the DMD-SLM. Experiments to estimate the impact of DMD manufacture errors on the formation of the correlation signal were performed. In these experiments it was found that to obtain a good result it is necessary to determine the size and position of the most flat area of DMD matrix, and to output the holograms on this area only. This limitation is caused by the fact that the surface of the matrix cannot be considered as perfectly flat, and using of its entire area for filter displaying will cause deterioration of the system resolution. The experiments on recognition of test objects in quasi-monochromatic spatially incoherent light on the implemented setup were performed. In these experiments, when the coincidence of the input and reference objects took place, localized correlation peak was observed. This fact demonstrates the successful objects recognition in such correlator.
Image segmentation algorithm in the system focusing digital camera
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The article discusses the segmentation algorithm of digital image based on the measurement contrast of fine detail in the normalized CIELAB system. Using normalized CIELAB system allows you to segment fine detail in accordance with the contrast sensitivity. Focusing the camera is carried out on the basis of the search of function maximum that determines the dependence of the number of segmented fine detail from the focal length. Proposed software as part of an interactive digital camera control system implements this function. The results of experiments and comparative analysis with other methods focus are given. It is shown that the proposed method improves the accuracy of the focus when photographing images in low light.
Azimuthal polarizer with phase shift for subwavelength focusing of laser light
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We have numerically and experimentally investigated subwavelength grating-polarizer that transform linearly polarized light of wavelength 633 nm into azimuthally polarized beam with a phase shift π at diametrically opposite points of the beam. This beam focused by Fresnel zone plate with focal length 532 nm produces focal spot with diameters equal to 0.42 and 0.81 of wavelength.
Informatics and computational method for inundation and land use study in Arctic Sea eastern Siberia, Russia
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Eastern Siberia, Russia is physically and socio-economically vulnerable to accelerated Arctic sea level rise due to low topography, high ecological value, harsh climatic conditions, erosion and flooding of coastal area and destruction of harbor constructions and natural coastal hazards. A 1 to 10m inundation land loss scenarios for surface water and sea level rise (SLR) were developed using digital elevation models of study site topography through remote sensing and GIS techniques by ASTER GDEM and Landsat OLI data. Results indicate that 10.82% (8072.70km2) and 29.73% (22181.19km2) of the area will be lost by flooding at minimum and maximum inundation levels, respectively. The most severely impacted sectors are expected to be the vegetation, wetland and the natural ecosystem. Improved understanding of the extent and response of SLR will help in preparing for mitigation and adaptation.
Studying of welding aerosol using laser granulometry
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The paper presents results of a study of the size of the particles that arise during the welding process using laser granulometry method. It is shown that the welding aerosol - extremely dangerous for human and animal health and the source of nano- and micro-sized particles.
Acoustic emission and magnification of atomic lines intensity originated by laser breakdown of salt water
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Research studies have been carried out the acoustic effects accompanying optical breakdown in water generated by focused laser and ultrasound radiation. Experiments were performed by using 532 nm pulses from a Brilliant B Nd:YAG laser. Acoustic radiation was produced by acoustic focusing systems in the form of hemispheres and rings at frequencies 10.7 kHz and 60 kHz. The experimental results show the sharply strengthened effects of acoustic emission from a breakdown zone by the joint influence of laser and ultrasonic irradiation. Various breakdown thresholds and character of acoustic emission in fresh and sea water are observed. The experimental result established that acoustic emission from optical breakdown of sea water in the presence and absence of ultrasound exceeds acoustic emission for the same experimental conditions in fresh water. Atomic lines of some chemical elements like sodium and magnesium were investigated for laser breakdown of water with the ultrasound field. The effect of magnification of these atomic lines resolution for salt water in ultrasound field was obtained. It is shown that the method of registration of acoustic emission from a breakdown zone allows to investigate thresholds and dynamics of laser breakdown which will be in accord with high-speed optical methods. The study revealed important practical applications of acoustic emission for breakdown and diagnostics of cavitation in opaque environments.
Electro-optic modulation of broadband radiation for the infrared spectral range
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The paper describes a method of electro-optical modulation for broadband radiation. Specifically, an analysis was undertaken of a broadband spectrum conversion for an infrared short-wave region with an optical spectral range (i.e., 0.74–2.5 μm. The effects of crystals’ geometry and the width of spectral ranges on the modulation depth of radiation were also considered. The proposed scheme allowed the depth of broadband radiation (not less than 80 percent with a change in crystal temperature) to be modulated and, due to the selected orientation of the optical elements, did not deteriorate the modulator’s characteristics.
Laser excitation of transversal and longitudinal polar modes in lithium niobate and tantalate crystals
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The excitation of longitudinal and transversal electromagnetic waves in lithium niobate and tantalate crystals is of interest for establish the conditions of coherent longitudinal and transversal waves generation in media and in vacuum. In this paper the results of laser excitation of transversal and longitudinal polar modes in these crystals are presented. We have measured spontaneous Raman spectra of lithium niobate and tantalate crystals in 0° (forward), 90°, and 180° (backward) scattering geometries. We have observed Raman peaks, related to fundamental transversal and longitudinal A1(Z) and E((X,Y) polar optical modes. In addition, there were pseudoscalar symmetry A2 peaks, forbidden by selection rules in Raman spectra for point group C3v. This was explained by reducing of the point group from C3v to C3 due to the presence of impurities in real crystals. Besides, the acoustic biphonon at low frequency has been observed. High intensity of spontaneous A1(Z)LO and A1(Z)TO Raman satellites gives the opportunity for generation of coherent longitudinal and transversal terahertz waves in lithium niobate and tantalate crystals with the help of Stimulated Raman Scattering under using high-power laser pumping. The presence of pseudoscalar and biphonons mode in low frequency region results in the strong interaction with fundamental soft mode and sharp central peak near the phase transition.
Collinear and vector interaction of light waves in nonlinear optical crystals KTiOPO4("KTP"), Ba2NaNb5O15 ("banana")
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Еsents the research results of biaxial crystals with mm2 symmetry class. These crystals were used for determining regularities of nonlinear conversion of broadband optical emission on the basis of collinear and vector light waves interactions of different nature.
The quantities of the basis nonlinear optical characteristics of "KTP" (KTiOPO4) and "banana" (Ba2NaNb5O15) crystals were calculated in case of synchronous conversion of broadband emission from the area of 0.8 – 2.8 micron to the visible spectrum of 0.4 – 0.7 micron.
The nonlinear optical characteristics of "KTP" crystals are defined by their geometrical structure, the mode of interaction of light waves, and the infra-red spectrum width, that was experimentally confirmed on "KTP" crystal.
The quality characteristics β were calculated for the "KTP" crystal. For "banana" crystal the angle of phase synchronism θc changes insignificantly when the observation plane is changed. It can be explained by the fact that the biaxiality of crystal is not strongly expressed, because of the basis refraction indices the conditions nz≤ny≈nx are performed.
Conversion of broadband IR radiation and structural disorder in lithium niobate single crystals with low photorefractive effect
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The conversion of broadband IR radiation when the noncritical phase matching condition is fulfilled in lithium niobate (LiNbO3) single crystals with stoichiometric (R = Li/Nb = 1) and congruent (R = 0.946) compositions, as well as in congruent single crystals doped with zinc has been investigated. It is shown that the spectrum parameters of converted radiation, such as the conversion efficiency, spectral width and position of maximum, depend on the ordering degree of structural units of the cation sublattice along the polar axis of crystal.
Effect of preparation conditions of calcium bismuthate based photocatalyst on its catalytic properties
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In this study, a series of calcium bismuthate samples having a different composition and type of crystal lattice was obtained. The diffuse reflectance spectroscopy found that both factors impact the calcium bismuthate ability to absorb the visible light irradiation. It was shown that the bandgap of synthesized photocatalysts depends on the degree of lattice defects. The catalytic activity of photocatalysts was studied in terms of decomposition rate of methylene blue by visible light in the presence of various samples of calcium bismuthate. It was found that the catalytic activity of calcium bismuthates with orthorhombic crystal lattice is lower than that of similar samples of rhombohedral lattice. Thus, samples with the lowest number of cation sublattice defects have the greatest catalytic activity.
Application of pyrolitic method of synthesis for preparation of calcium bismuthate based photocatalyst
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The study describes use of pyrolytic synthesis method for preparation of visible light calcium bismuthate based photocatalyst. The advantage of the proposed method is that it allows obtaining single-phase, homogeneous samples with various types of crystal lattice and controlled defects. It is shown that it is possible to obtain crystalline calcium bismuthate with the same stoichiometry in the entire region of existence of the solid solution. Synthesized samples of calcium bismuthate have been characterized using the scanning electron microscopy and X-ray analysis. It was found that the scope and conditions of synthesis affect the degree of imperfection of both anionic and cationic sublattice of calcium bismuthate.
Optical radiation characteristics that affect the formation of large-scale and small-scale optical defects in photorefractive crystals
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We have considered some special cases the interaction of optical radiation and photorefractive crystals. We gave special attention to the impact of the characteristics of optical radiation, the intensity, frequency and polarization of the wavefront onto the features of the large-scale and small-scale optical defects forming due to the photorefractive effect in crystals. We registered forming of the small-scale optical defects via observing of the photoinduced light scattering in photorefractive lithium niobate crystals. And we registered forming of the large-scale optical defects in lithium niobate crystals by the polarizers system. Lithium niobate crystals have significant electro-optical and photorefractive properties. They are convenient model for studying how the light waves propagate through the photorefractive crystals. The article discusses the results of the experiments.
Determination of electro-optic coefficients of lithium niobate crystal by polarization and interference methods
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In this paper electrooptical coefficients r22, [r13 − 0.9r33 ], of nominally pure single congruent crystal of lithium niobate are determined. Measurement of electro-optic coefficients is produced by two independent methods: polarization and interference. The polarization scheme is based on the Senarmont method and interference scheme - on conoscopic figures.
Structure disorder and photorefractive properties of LiNbO3:Zn crystals
Nikolay V. Sidorov,
Mikhail N. Palatnikov,
Natalya A. Teplyakova,
et al.
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Due to the Raman spectra structure changes were searched in a LiNbO3:Zn (0.04÷5.84 mol. %) single crystals series with the varying of the dopant concentration. Optical homogeneity and photorefractive properties were researched by photoinduced light scattering.
Structure disorder and photorefractive properties of LiNbO3:В crystals
Nikolay V. Sidorov,
Mikhail N. Palatnikov,
Natalya A. Teplyakova,
et al.
Show abstract
Raman spectra structure changes in a LiNbO3:В (0.08÷0.18 mol. %) single crystals with the varying of the dopant concentration were investigated. Photorefractive properties and optical homogeneity of lithium niobate single crystals were researched by photoinduced light scattering.
Secondary structure and optical properties of ferroelectric lithium niobate crystals
N. V. Sidorov,
M. N. Palatnikov
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Manifestation of the secondary structure of lithium niobate single crystals with low photorefractive effect was researched by Raman scattering and photoinduced light scattering (PILS). Laser induced static microdefects with changed refractive index were revealed. Shape and asymmetry of PILS patterns were demonstrated to depend on difference in refractive indexes and energies of ordinary and extraordinary beams. Nonmonotonicity of temperature dependence of Raman bands intensities was shown to be caused by gradual shutdown of photorefraction mechanisms at rise in the temperature that leads to decrease of laser radiation intensity. We have revealed an concentration area of high structure order in LiNbO3:Zn crystals. Raman bands that probably correspond to А2 symmetry scalar vibrations were detected in LiNbO3 crystals strongly doped by Zn and Mg.
The laser conoscopy of lithium niobate crystals of different composition
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In this paper we study conoscopic patterns of single crystals of LiNbO3 congruent (Li/Nb = 0.946) and stoichiometric (Li/Nb = 1) compounds, as well as congruent crystals doped with cations: Mg2+ (0.86 wt.%), Zn2+ (0.03, 0.52, 0.62 wt.%), Cu2 + (0.015 wt.%), B3+ (0.12 wt.%), Gd3+ (0.51 wt.%), Y3+ (0.46 wt.%), Gd3+ (0.23 wt.%): Mg2+ (0.75 wt.%), Mg2+ (0.86 wt.%): Fe3+ (0.0036 wt.%), Ta5+ (1.13 wt.%): Mg2+ (0.011 wt.%), Y3+ (0.24 wt.%): Mg2+ (0.63 wt.%). Conoscopic patterns of lithium niobate crystals were recorded at excitation by He-Ne laser (λo = 632.8 nm) and the second harmonic of MLL-100 laser Y:Al garnet (λo = 532 nm, P = 1mW), which does not cause the effect of photorefractive and more powerful radiation of the second harmonic MLL-100 laser Y: Al garnet (λo = 532 nm, P = 90 mW). Irradiation of crystals radiation 632.8 nm and 532 nm (P = 1 mW) photorefractive effect is absent and there is no disclosure of the photoinduced light scattering indicatrix. In this case, conoscopic paintings reflect the state of structural defects in the crystal in the absence of photorefractive effect. When excited by MLL-100 laser radiation on Y:Al garnet (λo = 532 nm, P = 90 mW) in conoscopic patterns appear as its own crystal defects (defined composition and crystal growth conditions), and defects, induced by laser radiation. These crystals characterized by rather a low photorefractive effect. In crystals with a low effect of photorefractive optical distortions associated with the passage of laser light through the crystal is not "smeared" the strong destruction of the laser beam due to photorefractive effect, and confidently observable.
Light beams interaction with highly effective holographic diffraction structure formed in polymer-stabilized liquid crystal under the impact of arbitrarily spatially inhomogeneous electric field
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In this work we developed the analytical model of highly effective diffraction on holographic diffraction structures in polymer-stabilized liquid crystals (PSLC) under the impact of arbitrarily inhomogeneous external electric field. The exact self-consistent analytical solutions are obtained by solving the system of coupled–wave equations describing the diffraction process by Riemann’s method. They takes into account the electrically-induced phase mismatch changing’s inhomogeneity caused by the strong adhesion between liquid crystal molecules and bounding surfaces. According to the obtained relations, numerical simulation of the diffraction characteristics under the influence of external fields with different form of spatial inhomogeneity was made. The simulation results show qualitative compliance with the earlier obtained results.
Formation and readout of holographic amplitude and phase non-uniform polarization gratings in polymer-stabilized liquid crystals
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In this work is we have developed the analytical models of holographic formation of polarization grating in polymerdispersed liquid crystals (PSLCs) by non-uniform recording field and its subsequent readout by uniform plane optical wave. The formation model is based on Jones formalism for recording field description and on equations of photoinduced Fredericks transition for description of dielectric tensor perturbations. The model of gratings readout is based on the system of coupled-wave equations solutions in the fixed-field approximation. Photo-induced absorption coefficient changing and the strong surface adhesion effects are taken into account. According to the obtained relations, numerical simulation of the spatial changing of the dielectric tensor was made for some forms of amplitude and phase non-uniformity of recording beams. For each complex of formation conditions the diffraction characteristics are also investigated numerically. The influence of recording field non-uniformity on grating’s diffraction characteristics is shown.
Orthogonal three-wave mixing in InP crystal
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The orthogonal geometry of three-wave mixing in non-gyrotropic photorefractive crystal (PRC) with cubic symmetry is proposed and studied. In this geometry a single phase-modulated object wave and two elliptically polarized reference waves are mutually orthogonal and propagate in crystal along its principal axes [100], [010] and [001], respectively. It is shown that each of two holograms recorded by pair of object and reference waves operates independently as a polarization-selective element and produces a demodulation signal which is related with one of two polarization components of the object wave. The resulting demodulation signal is a superposition of two demodulation signals originated from two holograms which are combined incoherently. It is shown that orthogonal geometry of three-wave mixing opens a possibility to design a completely polarization-independent adaptive interferometer.
Simulation of nonlinear effects at laser modification of the surface minerals with gold
E. A. Vanina,
E. M. Veselova,
N. A. Leonenko
Show abstract
Considerable interest are the studies related to the influence of powerful energy flows of natural gold-dispersed mineral medium, since such investigations lead to a new decision of technological problems of mineral processing. In this paper nonlinear effects occurring as a result of experimental studies using an ytterbium fiber laser source LS-06, with a wavelength 1060 nm, continuous action are studied. It was carried out modeling of these processes. Natural samples containing submicron gold were investigated, with identified local orderliness of ultrafine particles of gold. Observed ultrafast nonlinear processes are an open non-equilibrium system in the interaction of laser radiation with matter. The laser radiation can provide high speed local temperature changes in the material that leads to thermal strong interaction, concentration, charge and other streams. The possibility of integration of the noble metal particles in the processing of laser radiation with regard to the properties of gold dispersed samples is proved. Effectiveness of submicron gold laser sintering depends on the temperature distribution in the irradiated sample, which is determined by the parameters of laser radiation.
Mechanism of luminescence from porous silicon
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A strong nonlinear increase in the photoluminescence intensity under laser excitation at room temperature is found for porous silicon obtained by anodic oxidation. It is shown that the maximum photoluminescence intensity correspond to samples of anodically oxidized porous silicon in the intermediate oxidation state. Laser excitation is found to increase the intensity of vibrational modes in the O3 – SiH, Si-O-Si and Si-O-H configurations with respect to the Si-Hn mode intensity in IR absorption spectra. It is experimentally confirmed that the oxide structure on the surface of silicon crystallites and the structure of the Si/SiO2 interface determine to a great extent the photoluminescent characteristics.
Light induced mechanism of the bubble clusters formation
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The light induced mechanism of bubble clusters formation has been investigated experimentally. It was detected the accumulation of bubbles in the cluster in the light field in almost horizontal closed cell The shape and dimensions of the cluster match the mode structure of the laser spot. The nature of the phenomenon is based on the existence of the thermocapillary forces, which push a suspension of bubbles in a heated area, as well as there are the adhesion forces. The light induced bubble clusters are formed in the case of free-surface liquids also. The dynamical bubble cluster foundation is described on the liquid surface. It is shown that the presence of inhomogeneous heat radiation, effective interaction of bubbles with each other (in the case of free surface) and with the surface of a solid body (closed cells) may lead to the formation of stable bubble clusters at the developed convection.
Features of extraordinary ray propagation in an optically anisotropic birefringent prism
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Features of ordinary and extraordinary rays travelling through an optically anisotropic prism with total internal reflection on one of the faces are considered in the paper. Special attention is paid to the process of extraordinary ray reflection from the face of total internal reflection. Ray propagation was investigated for prisms made of four optically uniaxial crystals (TeO2, CaCO3, Hg2Cl2, Hg2J2) having different optical signs and values of birefringence. Possible ways of ray propagation through a prism at different angles of incidence on the prism and different directions of ray propagation within the prism were calculated. The examined features allow channels in fiber-optical communication systems to be split by optical means.
Transient gratings in the transparent nanoliquid
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In a gradient light field the nanoparticles in the transparent medium are controlled by the electrostrictive forces, causing changes in their concentrations. The medium is characterized by a cubic nonlinearity in this case that is correct only for small intensities of radiation. For large radiation intensities the potential energy of particle is more than heat one and it requires consideration of non-linearity of the highest order. In this paper the theoretical analysis of the light induced mass transport in the dispersed liquid medium is carried out for large intensities of radiation, when the change in concentration is greater than or comparable to the primary. It is shown the recording of the grating is a non-linear process and the phase grating becomes non sinusoidal. The amplitudes of the first harmonics increases in this case with the intensity of the light at the non-linear regime making possible the significantly increasing of the efficiency of holograms recording. We define the thermal nonlinearity in transparent nanosuspension occurred due to the heat when an electrostrictive stream of particles flows in a viscous fluid.
Direct laser welding of Sm and Fe powders for creation of magnetic alloys on the stainless steel substrate: microstructure and magnetic properties
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The testing of welding of Sm and then Fe powders was carried out on laser complex to create ferromagnetic coatings of (1-2) μm thickness in conditions of argon flow. X-ray diffraction analysis showed that oxidation of Sm and Fe occurs, but the main contribution of Fe grains in the structure was proved. It was established that in the conditions of the additional magnetic field (0.2 T) the crystallization of single Fe grains (5-20 μm) with formation of a mesh structure in Sm oxide matrix occurs on the whole thickness of the welded layer. The dissolution of Sm on the depth of 1.0-1.3 μm was observed inside the substrate with the formation of high density Sm oxide’s grains (2-10 μm), when the additional magnetic field is absent during laser welding. The Fe laser welding results in the formation of elongated Fe grains to a depth of 60-100 μm framed. Regardless of the microstructure samples showed similar magnetic loops with high saturation magnetization (110-112 emu/g), low coercivity (0-100 Oe) and near zero residual magnetization that corresponds to soft magnetic coatings with main contribution of Fe grains. Magnetic ordering was found in both coatings with Curie temperature of 50 K.
Structure and magnetic properties of alloys formed by the laser welding of Sm and Co powders on different substrates
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A modern robotic laser complex with neutral gas supply system of argon to protect the powders from oxidation has been used for laser welding of Sm and Co powders on stainless steel and duralumin substrates. X-ray diffraction investigation of crystalline structure showed that oxidation of mainly Sm occurs during laser welding and following cooling at the standard argon flow. The main ferromagnetic phases: Co and Co-Fe alloy on stainless steel substrate (sample No 3) and SmCo5 on duralumin substrate (sample No 5) were determined by data of magnetic measurements, including temperature magnetization measurements and magneto-optic Kerr microscopy. It was observed that sample No 3 at T = 300 K showed ferromagnetic properties with small coercive force (about 300 Oe) and high saturation magnetization of 44 emu/g. With temperature decreasing its magnetization monotonically increases to 50 emu/g and coercivity increases in three times that determined with ferromagnetic ordering of Co and Co-Fe alloy grains at various temperatures. The sample 5 showed weak ferromagnetic properties (saturation magnetization of ±27.8 emu/g and coercive force of 130-140 Oe) that determines only by SmCo5 grains inside the welded layer. Small coercive force for SmCo5 grains correlates with big sizes of its magnetic domains (20-150 μm).
An influence of formation methods of laser layer’s welding on their phase composition and magnetic properties
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Comparative study of laser welding method has been carried out at four different methods of welding in Sm-Co system on two types of substrates: stainless steel and duralumin and at two types of argon gas flow in the place of melting. The comparison of compositions and magnetic properties of welded coatings has been done for all formed samples. It was established that SmCo8.5 compound conserves only after laser welding of SmCo8.5 tablets with additional contribution of oxides that results to strongly decrease of saturation magnetization and coercivity as compared with SmCo8.5 films. In the case of the standard argon gas flow and using of Sm and Co powders the quick melting of the stainless steel substrate surface occurs that results to strong diffusion of transition metals to the welded layer and formation of Sm-based, noncrystalline alloy with only two crystalline phases (Co0.72Fe0.28 and Co), which demonstrate soft ferromagnetic properties. The formation of Sm-Co chemical compound is blocked when the Co welding carried out after Sm welding due to formation of Sm oxides on the welding surface. In the conditions of a stable argon atmosphere around the sample the pure Co and Sm crystals have been formed with weak ferromagnetic properties.
Magnetic properties of laser welded coatings from Sm and Fe powders with and without magnetic field on Al based substrate
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Two step laser’s welding of Sm and Fe powders on duralumin substrate in the argon gas flow has been firstly tested. It was established that oxidation of Sm atoms with formation of Sm2O3 and SmO during laser welding of duralumin substrate is the main reason of not forming of the SmFex compound, which can be appeared on the second step of Fe laser welding. The next reason is a strong interaction between Al and Sm atoms at the interface with a substrate with formation of Al2Sm compound, consisting from paramagnetic atoms. So, an additional protection from oxidation needs during laser welding. Magnetic properties of coatings formed by layer-by-layer laser welding from Sm and Fe powders on duralumin AMg-3 substrate welded with and without external magnetic field have been studied by methods of field and temperature magnetization measurements and study by vibromagnetometer method at room temperature (300 K). A strong paramagnetic contribution of AMg-3 substrate has been proved. Al2Sm grains without substrate have shown soft ferromagnetic properties at 300 K independently from using an external magnetic field. An interesting phenomenon has been found at cooling coatings down to 4 K: magnetic ordering of Al2Sm domains with Curie temperature about 70 K.
Optimization of the fiber laser parameters for local high-temperature impact on metal
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This paper presents the local laser heating process of surface layer of the metal sample. The aim is to create the molten pool with the required depth by laser thermal treatment. During the heating the metal temperature at any point of the molten zone should not reach the boiling point of the main material. The laser power, exposure time and the spot size of a laser beam are selected as the variable parameters. The mathematical model for heat transfer in a semi-infinite body, applicable to finite slab, is used for preliminary theoretical estimation of acceptable parameters values of the laser thermal treatment. The optimization problem is solved by using an algorithm based on the scanning method of the search space (the zero-order method of conditional optimization). The calculated values of the parameters (the optimal set of "laser radiation power - exposure time - spot radius") are used to conduct a series of natural experiments to obtain a molten pool with the required depth. A two-stage experiment consists of: a local laser treatment of metal plate (steel) and then the examination of the microsection of the laser irradiated region. According to the experimental results, we can judge the adequacy of the ongoing calculations within the selected models.
Photoelectric element on the basis of the sandwich metal-ferroelectric-metal structure
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It was described the photoelectric element on the basis of thin sandwich metal-ferroelectric-metal system. The effect was observed in doped lithium niobate crystal with two electrodes of different metals. The current value increases dramatically when you reduce the thickness of the crystal. The effect is observed only in doped lithium niobate crystals and has a maximum for concentrations of impurities of iron around 0.3 weight. % . This paper proposed thermal model of the investigated phenomena resulting from field contact potential difference on the borders of section of metal-ferroelectric material. The results obtained can be used to develop radiation receivers, as well as in the interpretation of experimental results on studying the properties of sandwiched metalferroelectric-metal structure.
Light fields generated by LC focusing device in different operational regimes
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The types of light fields that can be generated with the use of proposed by the authors 4-channel modulator (LC focusing device) in different modes depending on the value of χl (where χ is the modal parameter, l – the characteristic size of the aperture and the square of χl is the ratio of the resistance of the high resistance layer and the impedance of the LC layer) are analyzed. By means of numerical simulation it was shown that χl value determines reshaping of equipotential lines of voltage from ring/ellipses to square/parallelogram contours or octagon contours. The capability of LC focusing device to generate light fields with intensity distribution in the shape of intersections, sets of points, boundaries of squares, diamonds, parallelograms, octagons is demonstrated. Obtained light fields can be useful in the problems of optical manipulation.