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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.