The electrostrictive mechanism of optical nonlinearity in the artificial Kerr-like medium is analyzed. The recording of the dynamic hologram is significantly non-linear process at high intensities of radiation. It is shown that the nonlinear differential equation for a nanosuspension can be reduced to a Hamiltonian system of equations. The exact solution can be obtained for the nonlinear problem in disregard of the diffusion. The calculation gives expression for the space and time dependence of the concentration profile of the nanosuspension, which is valid at short times.
The electrostrictive mechanism of optical nonlinearity in the artificial Kerr-like medium is analyzed. The recording of the dynamic hologram is significantly non-linear process at high intensities of radiation. The model of the nonideal gas of nanoparticles includes the second virial coefficient only and allows the exact solution of the nonlinear equation. The amplitude of phase grating depends exponentially versus intensity but it saturates at the high filling factor due to the repulsion effect.
The electrostrictive orientational mechanism of optical nonlinearity in the artificial Kerr-like medium with nonspheroidal nanoparticles is analyzed. The thermal contribution to the cubic nonlinearity of transparent nanosuspension takes into account for the first time. The exact solution was obtained for the light induced lens response in a one-beam scheme. It is shown that thermal response reduces the value of electrostrictive nonlinearity for the shot time period and disappears in the stationary state.
We present a new pump-probe laser beams configuration of the thermal lens method for the nonlinear optical diagnostics of nanosuspensions. Trial-beam scheme eliminates the influence of the electrostrictive and light pressure effects and thus provides the more precise determination of thermodiffusion coefficient of nanoparticles. A mathematical model has been introduced to describe the thermo- and mass transfer in a nanofluid in a dual-pump beam field. The results are relevant to the study of the radiation self-action in the nanosuspension and optical diagnostics of such materials.
It was described the light induced currents in thin metal-ferroelectric-metal sandwich system. The effect was observed in doped lithium niobate crystals with two electrodes of different metals. The light induced response includes the photovoltaic effect and the thermoinduced effect. It was proposed the model of the investigated phenomena resulting from field contact potential difference on the borders of section of metal-ferroelectric material.
The theoretical analysis of the dynamic holograms efficiency in the transparent nanosuspension is carried out. It was compared the two-wave scheme of the dynamic holography and the four-wave mixing method. The mechanism of optical nonlinearity of the medium is due to the forces operating on the particles of the dispersed phase in light field (electrostrictive nonlinearity). The peculiarities of the kinetics of the both nonlinear processes were discussed. The results are relevant for dynamic holography in the nanosuspension, as well as for optical diagnostics of such media.
The theoretical analysis of the light induced mass transport task was executed in the nanosuspension 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 using of high intensities of the reference beam allows significantly increase the efficiency of the beam deflection method. The results are relevant in the study of the dispersed liquid media, as well as optical diagnostics of such materials.
The comparative analysis of the non-resonance mechanisms of cubic optical nonlinearity in aerosols was carried out. The analysis includes the thermal nonlinearity (thermal expansion of the materials) and the concentration nonlinearities caused by electrostriction and thermodiffusion effects as well as the reorientational cubic response. It is showed that the greatest values of nonlinear coefficient are provided by thermodiffusion and electrostrictive mechanisms of concentration nonlinearity. The results are relevant for nonlinear optics of aerosols, as well as optical diagnostics of such media.
It was analyzed the self-focusing regime of the Gaussian beam in the nanosuspension with electrostrictive nonlinearity. The theoretical analysis of the light-induced mass transfer in the nanosuspension was carried out for large intensities of the Gaussian beam radiation, when the concentration change is comparable to the primary. The nonlinear lens in this mode is the exponential function of the incident light intensity. It is shown that the critical power value decreases significantly for high intensity beam. The results are relevant to the study of the radiation self-action in the nanosuspension and optical diagnostics of such materials.
The theoretical analysis of the light-induced mass transport task was executed in the dispersed medium in a homogeneous light field. We have discussed the model of sedimentation of nanoparticles by using the laser effect in liquid. It was received the solution of one-dimensional task of the light induced mass transfer as depending on intensity of laser beam. The proposed model of sedimentation of nanoparticles is relevant in the study of dispersed liquid-phase media, as well as in the optical diagnostics of such materials.
This paper analyzed the light induced lens response at the fiber optics scheme in transparent nanosuspension with electrostrictive nonlinearity. Ii was proposed the simple model of the phenomenon which can be used for describing the fiber optics experimental results in the nanosuspension. The received expression shows the monotonous growth (as the parabolic low) of the collected power versus the input power in ideal gas model of the nanoparticles ensemble. The thermal contribution due to Dufour effect is characterized by the negative sign and decreases the total response. The results are relevant to the study of the nonlinearity of the nanosuspension and optical diagnostics of such materials.
It were analyzed the Dufour effect in the transparent nanosuspension in a light field. The space non-uniform light field generates the nanoparticles flow due to electrostrictive gradient forces. The concentration flow generates the thermal flow due to the Dufour effect and therefore the thermodiffusion (Soret effect). The dynamic holography method is proposed for the investigation of those phenomena. The Dufour thermal response and the thermodiffusion phenomenon both change the magnitude and relaxation time of the electrostrictive hologram. The results are relevant to the optical diagnostics of the nanosuspensions and nanofluids.
A theoretical model of the pseudo-prism method for diagnostics of two-component media in a gravitational field is considered. An expression is obtained for the angle of deflection of the probe signal with allowance for the Dufour effect.
It were analyzed the nonlinear optical methods of diagnostics of binary mixtures - the thermal lens method and dynamical holography method. In two-component fluid (binary mixture) the heat flow can cause concentration stream arising from occurrence of thermodiffusion phenomenon (Soret effect). As a result these phenomenon changes the magnitude of the transport coefficients of the mixture. It was developed the theory of the light induced heat and mass transfer, taking into account the cross interaction between the heat and mass flows as well as the presence of optical feedback. The results are relevant to the optical diagnostics of the binary liquid mixtures and nanofluids.
We have discussed the theoretical model of sedimentation of nanoparticles by using the laser effect in liquid. It was received the steady-state solution of one-dimensional task of the light induced mass transfer as depending on intensity of laser beam. It is shown that it can allow to divide polydispersive mixtures. The proposed model of sedimentation of nanoparticles is relevant in the study of dispersed liquid-phase media, as well as in the optical diagnostics of such materials.
The theoretical analysis of the dynamic holograms efficiency in the dispersion liquid medium is carried out. The mechanism of optical nonlinearity of the medium is due to the forces operating on the particles of the dispersed phase in light field. The summary nonlinear response of the nanosuspension includes two concentration mechanisms (electrostrictive and thermo-diffusive) and two thermal ones (light absorbing and particles drift caused by light pressure). The results are relevant for dynamic holography in the nanosuspensions, as well as for optical diagnostics of such media and thermo-optics spectrometry.
In two-component fluid (binary mixture) the heat flow can cause concentration stream arising from occurrence of thermodiffusion phenomenon (Soret effect). As a result these phenomenon changes the magnitude of the transport coefficients of the mixture. In this paper the theoretical analysis of the light-induced thermodiffusion mass transfer in two-components liquid in a field of Gaussian beam was carried out. It was calculated a concentration contribution to the thermal lens response in the z-scan method.
This paper proposes a way to create pseudo-prisms in the nanodispersive liquid through the light radiation pressure. The theoretical analysis of the light induced mass transport task was executed in the nanosuspension 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.
A light induced drift of nanoparticles in a transparent viscous medium was discussed. The heating of the transparent dispersive medium under the influence of forces of light pressure and Dufour effect in a Gaussian light field was analyzed.
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.
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.
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.
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.
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.
We have theoretically studied the optical transmittance response of thin cell with liquid containing absorbing nanoparticles in a Gaussian beam field. The transmittance spatial changing is caused by thermal diffusion phenomenon (Soret effect) which produces the variations of concentration of absorbing nanoparticles. The thickness of optical cell (including windows) is significantly less than the size of the beam. As a result, an exact analytical expression for the one dimensional thermal task is derived, taking into account the Soret feedback that leads to the temperature rising on the axis of a Gaussian beam. We have experimentally studied this phenomenon in carbon nanosuspension.
The thermal lens scheme is proposed for a thin layer of two-component liquid in the cell which thickness is significantly less than the size of the beam. As a result, an exact analytical expression for the thermal lens response is derived, taking into account the thermal lens in the windows of the cell.
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