The measurements of the angular distribution of two-photon-excited fluorescence of a dye solution in an aqueous aerosol are reported. It is shown that the fluorescence of an aerosol with a dye is one and a half to two times greater in the backward direction than in the forward direction.
The experimentally obtained dependences of acoustic signals on the energy of femtosecond pulses in the filamentation mode, propagating in a liquid-drop aerosol with nanoparticles of various concentrations imitating Aitken nuclei, are presented. It is shown that, under the action of a femtosecond pulse filament, a water aerosol jet breaks into two jets.
The results of experimental studies of filamentation of focused laser pulses of nanosecond megawatt duration in a medium with strong cubic nonlinearity are presented. It was shown that multiple small-scale beam self-focusing is observed, the nonlinear focus is much closer to the source than the geometric one, and this distance increases with an increase in the pulse energy (power). Long tracks are observed that are uncharacteristic of linear spatial focusing.
The studies have shown that films with different thicknesses, but practically identical transmittance values, give absolutely different results. This suggests that in addition to transmission, the generation characteristics are significantly affected by the thickness of the matrix being researched.
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.
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.
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).
The paper presents the results of researching surface plasmon polaritons dispersion on the "composite medium and metal substrate" border within a visible wavelength range. The composite dielectric function varies in space according to the periodic law. The solution to this problem has been presented as an inhomogeneous wave for which the field amplitude distribution has been written in an analytical form and dispersion relations have been obtained.
The article presents the results of computing simulation of surface plasmon-polaritons’ dispersive properties at the interface between «a composite medium based on Al, Ag, Ni, Cu nanoparticles and a substrate made of the same metals» in the visible wavelength band. It is shown that the surface plasmon-polaritons’ dispersive properties in these structures can be changed in a wide range by altering the nanoparticles concentration.
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.
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.
In the paper comparative evaluation of the photon mean free path in the system of metal nanoparticles and dielectric matrix is performed by means of numerical simulations. As a material of nanoparticles both metals (Ag, Cu) in which the frequency of plasmon resonance falls in the range under study and metals (Al, Ni) in which the plasmon resonance frequency is far from the investigated range have been used. The research has shown that for the studied metals the media based on Al nanoparticles satisfy best the Ioffe-Regel criterion for photons of visible wavelength range.
The aim of experimental investigations is study of nonlinear optical acoustic effect during interaction of femtosecond
laser pulse (FLP) with laboratory air both in area of laser beam filamentation and outside it.
Were experimentally investigated nonlinear optical effects at propagation of laser pulses with length of a wave 0,82 microns and duration 80 fs in liquid aerosols and the drops containing organic dyes. Frequency of recurrence of laser pulses of 90 MHz, energy in a pulse 3,5 nJ, average capacity of radiation up to 340 mW. Registration of spectra of stimulating radiation and a luminescence of a drop was carried out with the sanction of 0,3 nanometers. Capacity of radiation varied turn of Glan prism. Results of measurements doublephotons are submitted to the excited luminescence in the suspended millimetric drops with dye and with filling nanoparticles of silver. Factors transparent and absorbing aerosol environments for laser continuous and fs radiations with length of a wave 0,82 microns and on length of a wave of continuous probing radiation with length of a wave 0,63 micros are received. Dependences of factor transparent the aerosol environment from concentration of an aerosol and capacity of laser pulses are submitted. Comparison of distribution of laser pulses fs duration with distribution of continuous radiation of the same length of a wave is carried out. Optical breakdown on absorbing particles of the aerosol environment is fixed at capacity of influencing radiation with fs duration exceeding 200 mW.
This paper presents the results of experimental investigations into the interaction of laser pulses of femtosecond duration with aerosol having various composition (aqueous aerosol, dye solution with embedded nanoparticles), as well as with individual particles in the case of two-photon induced stimulated fluorescence. The acoustic method was employed to study the decay of the energy of the filament generated at different focusing, as well as the transmittance of the filament energy as it passed through the aerosol layer.
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 approximately 10 ns and wavelengths of 1064 and 532 nm) is experimentally investigated. It is 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 approximately 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.
Amplification of stimulated Raman scattering (SRS) radiation of ethanol in a polydispersion of microdroplets of ethanol solution of Rhodamine C is obtained experimentally when irradiating the droplets with laser pulses of 0.532 micrometer wavelength.
Amplification of stimulated Raman scattering radiation of ethanol in a polydispersion of microdroplets of ethanol solution of Rhodamine C is obtained experimentally when irradiating the droplets with laser pulses of 0.532 micrometers wavelength.
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