Mishik A. Kazaryan

Brightness Amplifiers In Optical Systems

Brief review of the last results on laser brightness amplifiers for different optical systems is given. Nonlinear properties of these systems and some new effects connected with the saturation of active medium of amplifiers are discussed. Some possible applica-tions (processing of microobjects, projection on large screen, TV-projection ...) are described.

Characteristics of inductive coaxial copper vapour lasers

We present new results on numerical investigation of characteristics of pulse-periodic inductive copper vapour lasers. In these lasers pump pulses are trains of high-frequency (~ 30 MHz) current oscillations repeated at a frequency of 2-17 kHz. An inductive laser with an annular working volume of 1.7 l was considered and its possible output parameters were studied. We analyze specific features of working medium excitation in an HF-discharge; diversity of the obtained laser pulse shapes and possible applications are discussed as well.

Influence of approximation range of the hologram transmission spectrum on the inverse problem solution

Transmission spectra of holographic sensors based on the Denisyuk holograms with silver nanograins embedded in the polymer matrix are investigated. It is necessary for the determination of the operation mode and of optical parameters of the sensors. The spectra have a narrow Bragg dip against a background decreasing with decreasing the wavelength. Three parameters of this dip determine the operating mode of the sensor. To calculate them, it is necessary to know 3 background parameters. All the parameters are calculated from fitting curves based on the formula proposed earlier which approximates the experimental spectrum quite well. It turns out that the spectral interval chosen for fitting is important and a solution exists not over any interval. When it exists, the parameters of the dip (the main goal of our work) are determined with a good accuracy. As for the optical parameters of the background, those associated with light scattering and with absorption seem to be strongly related. Changing the fitting interval leads to a correlated change of the values of parameters, sometimes considerably. Nevertheless, the fitting function approximates the experimental spectrum quite well and the accuracy of determining the Bragg dip is high.

Effect of iron oxide nanoparticles on the blood coagulation according to light scattering data

The work shows that iron oxide nanoparticles obtained in acoustoplasma discharge with cavitation affect the rate of one of the reactions of the process of blood coagulation - cleavage of fibrinogen by thrombin. As a result of the reaction, a fibrin gel is formed. By means of dynamic and static light scattering we reveal that adding of thrombin initially mixed with nanoparticles to the fibrinogen solution leads to dramatically acceleration of gel formation. Adding of nanoparticles to the solution of fibrinogen (before thrombin addition) leads to stopping of the reaction at the first stage (without gel formation). This data shows that ferrous oxide nanoparticles can act as regulators of enzyme reaction - in one case accelerating it, and in the other - by inhibiting it. Previously we presented the dynamics of distributions of the scattered light intensity on particle sizes in the fibrinogen-thrombin system with various sequences of nanoparticle addition. In this work we showed dynamics of the intensity correlation function in the samples, whose form becomes close to “stretched exponent” in pregel state or power law in a gel.

Ag nanoparticles suspensions for stimulated Rayleigh backscattering of single frequency 0.5 micron pulsed laser radiation

The spectral characters and increments of stimulated Rayleigh scattering in pure liquids and suspensions of Ag nanoparticles in toluene and hexane of principally different nature were investigated in this work. The correlation of two photon absorption spectra and stimulated scattering efficiency were discovered and analyzed. It is shown experimentally that the frequency shift of the scattered signal relative to the pump frequency greatly exceeds the theoretical value.

Non-linear optical properties of nanosized metal oxide particles obtained in plasma discharge in liquid phase under ultrasonic cavitation

The nonlinear response of metal oxide nanoparticles obtained by the acoustic plasma method is measured in aqueous disperse systems at a wavelength of 532 nm. Induced absorption is detected in the Cu2O, WO3 and ZnO disperse systems, and bleaching is detected in the Fe2O3 system. The real and imaginary parts of nonlinear third-order susceptibilities are determined.

On one mechanism of light ablation of nanostructures

The mechanism of mechanical ablation of nanoparticles during the interaction with a high-power laser radiation pulse is proposed. A particle is polarized under a laser electric field, and electric forces acting on field-induced oppositesign charges cause rupture stresses. Upon reaching the stresses exceeding the maximum allowable values for a given material, a nanoparticle decays into two ones. This effect can be used for narrowing the size distribution of nanoparticles produced by the laser ablation method.

The effect of tungsten on the properties of gold-doped silicon

The effect of the tungsten coating on the photoelectric and electrophysical properties of electron-silicon samples after gold diffusion was analyzed. The trap levels associated with tungsten atoms, with a tungsten complex + vacancy, and with an oxygen + vacancy complex were detected. In samples of silicon doped with gold, both with and without a tungsten coating, the resistivity increased by 2-3 orders of magnitude, which indicates the creation of additional energy centers associated with gold and gold complexes caused by tungsten. At the same time, the time of nonstationary relaxation photoconductivity has greatly decreased, which also indicates the creation of additional recombination centers and trap levels.

Effect of iron oxide nanoparticles on the concentration-versus-sizes relation of proteins in the blood plasma and serum, and in model solutions

The effect of iron (III) oxide nanoparticles produced in acoustoplasma discharge with cavitation on the concentration and the sizes of particles in model protein solutions, human blood serum and plasma samples is studied. Dynamic and static light scattering data on size and concentration of particles show that the nanoparticles addition to fibrinogen-thrombin system affects the course of enzymatic reaction. Interaction of nanoparticles with fibrinogen solution (before thrombin addition) does not significantly change the distribution of scattered light intensity on particle sizes. Comparison of the relations of particle sizes and their concentration for fibrinogen solution with and without nanoparticles shows an increase of the slope of size-concentration relation in a log-log scale, which indicates an increase in the concentration of small particles and decrease of big ones. For model solution of fibrinogen with thrombin, initially incubated with iron oxide nanoparticles, the slopes of the size-concentration relation equals to k = –(4.62±0.33) and slightly differs from the slope of the relation for fibrinogen-thrombin system without nanoparticles k=–(4.23±0.28). We believe that changes in the size-concentration relation indicate the interaction of nanoparticles with proteins, which results in gelation rate change.

Laser-induced dissociation processes of protonated glucose: dehydration reactions vs cross-ring dissociation

Studying the processes occurring in biological systems under irradiation is critically important for understanding the principles of working of biological systems. One of the main problems, which stimulate interest to the processes of photo-induced excitation and ionization of biomolecules, is the necessity of their identification by various mass spectrometry (MS) methods. While simple analysis of small molecules became a standard MS technique long time ago, recognition of large molecules, especially carbohydrates, is still a difficult problem, and requires sophisticated techniques and complicated computer analysis. Due to the large variety of substances in the samples, as far as the complexity of the processes occurring after excitation/ionization of the molecules, the recognition efficiency of MS technique in terms of carbohydrates is still not high enough. Additional theoretical and experimental analysis of ionization and dissociation processes in various kinds of polysaccharides, beginning from the simplest ones, is necessary. In our work, we extent previous theoretical and experimental studies of saccharides, and concentrate our attention to protonated glucose. In this article we paid the most attention to the cross-ring dissociation and water loss reactions due to their importance for identification of various isomers of hydrocarbon molecules (for example, distinguish α- and β-glucose).