V. A. Donchenko

Scattering properties of spherically aggregated metal nanoparticles in active matrix

According to the model of the effective medium and G. Mie theory, attenuation cross-sections, cross-sections for scattering and absorption for metal nanoparticles nanosized aggregates have been assessed depending on the aggregate’s size , level of the aggregate’s filling with nanoparticles and physical properties of the nanoparticles material.

Debye potentials for heterogeneous media

The paper presents the results of the Helmholtz equation solution by the method of perturbation theory in the spherical coordinate system for the Debye potentials for weakly heterogeneous media based on metal nanoparticles and the dielectric matrix. In that case, the dielectric function of a composite changes in space in the radial direction.

Scattering properties of a radially heterogeneous sphere made of metal nanoparticles and the dielectric matrix

The cross-sections of attenuation, scattering and absorption of spherically aggregated metal nanoparticles in dependence on the aggregate size, the degree of its filling with nanoparticles and physical properties of nanoparticle material have been estimated, according to the model of the effective medium and the theory of G. Mie. In that case, the concentration of the nanoparticles changes radially.

The laser generation threshold characteristics of a colloidal solution of gold and platinum nanoparticles with rodamine 6G

In the work the spectral-energy characteristics of stochastic (non-resonator) laser generation of a thin layer of organic dye Rhodamine 6G solution with the addition of gold and platinum nanoparticles in the form of a colloidal solution in ethanol have been experimentally investigated. It has been experimentally established that the generation thresholds are reduced by two orders when adding nanoparticles to the active medium. It is shown that the use of nanoparticles having a plasmon absorption band in the region of the agitation radiation does not lead to a significant change of the active medium generation thresholds.

Properties of lasing in Rhodamine 6G solutions with nanoparticles free of plasmon resonance

The threshold characteristics of lasing in a 20-μm layer of colloidal solution of Rhodamine 6G dye with plasmon-resonance Au nanoparticles and non-plasmon-resonance Pt nanoparticles excited by 532-nm radiation are experimentally studied. The spectral dependence of the scattering and absorption cross sections of gold and platinum nanoparticles are calculated within the Mie theory. It is found experimentally that the addition of nanoparticles to the active medium decreases the lasing thresholds by two orders of magnitude. It is shown that the lasing thresholds are 1.5–2 times lower when adding gold nanoparticles than when adding platinum nanoparticles of the same concentration.

The influence of plasmon resonance on the decrease of resonatorless laser generation thresholds

The paper presents the results of the measurements of the values of resonatorless laser generation power threshold densities in thin layers of 6G rhodamine colloidal solutions with single plasmon-resonance gold and silver nanoparticles and non-plazmon resonance nanoparticles of platinum and zinc oxide. It is shown that when gold, platinum and silver nanoparticles are used, the thresholds values are approximately equal at the same concentrations.

Reflectivity dispersion characteristics of the composite films on the metal substrate

The paper gives the results of computer simulating reflectivity of a flat structure made of composite material on the basis of Ag, Ni, Al, Cu nanoparticles and a substrate of the same metals within the visible wavelength range. The possibility of broadband optical antireflection of a metal surface using nanoparticles of the same metals by forming in the near surface layer of the metal being made anti-reflecting a composite layer is researched. Within the visible wavelength range the dispersion characteristics of the reflectivity of the composite metal-dielectric layer on a metal substrate have been calculated for different values of the filling factor and the thickness of the composite layer both for the metals having plasmon resonances (Ag, Cu) within the visible range and for the metals plasmon resonances of which do not fall in the visible wavelength range (Al, Ni).

Threshold characteristics cavityless lasing in composites with agglomerated metal and dielectric nanoparticles

The paper presents results of experimental studies of the threshold characteristics of lasing in thin layers (20 microns) of a solution of rhodamine 6G with agglomerates of metal and dielectric nanoparticles. The maximum decrease in the lasing threshold was more than two orders for a wide range of changes in the concentration of metal agglomerates. For dielectric nanoparticle agglomerates range of maximum lowering of the threshold is 5 times lower. This is due to different mechanisms of formation of lasing in these environments.Comparing the efficiency of lasing in layers with metal agglomerates proves on expediency using them to create a low threshold microlasers.

Spectral shaping of lasing active medium with agglomerated nanoparticles of metals and dielectrics

In this paper presented a series of experiments determine the spectral characteristics of random lasing in lasers with agglomerated nanoparticles metals and dielectrics. The data allowed us to establish that, in the active heterogeneous environment, there are various gain effects of lasing the impact of which is determined nanoparticles concentration.

Mathematical modeling of space-time profiles of heterogeneous media temperature

On the basis of an analytical solution of a one-dimensional (in cylindrical coordinates) heat equation homogeneous medium with a heat source, due to the linear absorption of light, we obtained analytical expressions for the calculation of space-time profiles of the increment of temperature in heterogeneous media based on metallic nanoparticles and a dielectric matrix.