Al. A. Zemlyanov

Interaction between gigawatt laser pulses and liquid media: Part 1. Explosive boiling of large individual water droplets

The results of experiments on femtosecond GW laser pulse interaction with isolated millimeter-size water droplets are presented. The temporal and spatial dynamics of optical breakdown in a liquid particle is investigated. The mechanical fragmentation of the droplet as a result of the evaporation and explosion of superheated areas is also discussed. The spectral characteristics of water particle glow during its explosive boiling are investigated.

Spectral and temporal characteristics of fluorescence of drops comprising dissolved dye excited by the IR laser radiation

Fluorescence of solutions of rhodamine 6G in the form of single drops of millimeter sizes excited by the intense IR and visible laser radiation (with duration of laser pulses of ∼10 ns and wavelengths of 1064 and 532 nm) is experimentally investigated. It was found that the power thresholds of fluorescence excitation for drops comprising the dissolved dye are, by an order of magnitude, less than for a cell with dissolved dye. The dichromatic drop fluorescence has been revealed, which is manifested through the occurrence of two maxima in the fluorescence spectrum of drops comprising dissolved rhodamine 6G. The first maximum coincides with that of the dye fluorescence spectrum, while the second maximum is shifted by ∼1000 cm−1 and is on the slope of the fluorescence line profile. It is shown that the duration of drop fluorescence does not exceed the duration of the exciting pulse.

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.

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.

Lasing efficiency in microlayers of active medium with agglomerated aluminum or silver nanoparticles

It is experimentally shown that the introduction of agglomerates of aluminum or silver nanoparticles with a concentration of the order 107 cm-3 into the ethanol solution of R6G with 20 microns thickness of microlayers decreases the threshold lasing by about two orders of magnitude is compared to the threshold of stimulated emission in a microlayer of pure ethanol solution R6G.

Far-field temporal dynamics of a laser beam passed through a thin nanocolloidal layer

We report on the experimental results of the temporal dynamics and formation of far-field diffraction patterns obtained when a low-intensity laser beam passes through a thin cell with metallic nanocolloids. The steady state structure of the intensity distribution on a distant screen is shown to be formed in a few seconds starting from the moment of laser beam incidence on the colloid and consists of several coaxial bright and dark rings. The ring’s diameter and number are varied depending on the solvent type and optical thickness of the colloid. The diffraction patterns depend also on the particle concentration and laser power. The theoretical interpretation of the observable peculiarities of diffraction pattern dynamics is carried out based on the free-space Kirchhoff diffraction integral and the analytical solution of the heat transfer equation for a light absorbing medium.

Effects of Stimulated Radiation in Liquid Particles and Drops with a Dye

Results of our investigations of stimulated radiation in polydisperse aerosols and drops of dye solutions aimed at developing methods of Raman spectroscopy of aerosols and creating efficient laser sources and frequency converters on the basis of liquid microresonators are given in the present paper.

Remote Detection of Asymmetric Dimethylhydrazine in the Atmosphere

The possibility of remote atmospheric detection of an ecotoxicant (asymmetric dimethylhydrazine) by means of a fluorescing mark is considered. The effect of asymmetric dimethylhydrazine on the spectral-luminescent properties of rhodamine 6G, nonsubstituted rhodamine, and amino- and hydroxysubstituted derivative of phenalenone is studied. It is shown that the molecules containing amino groups change their spectral properties and lose emitting properties in the presence of dimethylhydrazine. The hydroxysubstituted derivative of phenalenone in dimethylhydrazine generates laser radiation when pumped by a Nd:YAG-laser and shows the stimulated fluorescence effect in aerosols.