Optics and Spectroscopy (v.118, #3)

The probabilities of the electric-dipole transitions 3d 94p, 3d 94f-3d 10, 3d 94s, and 3d 94d in the spectra of nickel-like ions Kr IX, Sr XI, Y XII, Ru XVII, Pd XIX, and Ag XX are calculated semiempirically with the use of published energy levels.

Spatial localization of atomic populations in the field of stationary waves by E. A. Efremova; M. Yu. Gordeev; E. Yu. Perlin; Yu. V. Rozhdestvenskii (342-349).
The spatial localization of populations in internal states for three-level -atoms and four-level atoms in the N-configuration in the field of spherical light waves is considered. It is shown that the widths of spatial distributions for atoms in certain internal states as they interact with the field of standing waves amount to only several tens of nanometers.

Development of multiple-wavelength oscillation in plasma of a pulse-periodic He + Ne + Sr laser by T. M. Gorbunova; A. N. Soldatov; Yu. P. Polunin; A. V. Lugovskoi (350-356).
Mechanisms of multiple-wavelength oscillation at the lines of He I, Ne I, Sr I, and Sr II ions in the active medium of a high-voltage pulse-periodic laser based on a He + Ne + Sr mixture at a total pressure of ∼200 Torr and duration of the current pulse of about 150–300 ns are analyzed. An important role played by collisional thermal mixing of the laser levels of Ne I and Sr I in multiplets, as well as by collisions of the second kind between metastable and unexcited atoms, in populating and depopulating atomic levels is demonstrated. Absolute populations of the upper and lower levels of the laser transitions in Ne I are found. It is discovered that the degree of ionization nonequilibrium of plasma, both during and after the pulse of current, determines the mechanism of population inversion in laser transitions.

Spin-polarization calculations of the electronic structure of intermetallic compounds DyNi5 − x Cu x (x = 0, 1, 2) are performed in the local spin density approximation with strong electron correlations in the 4 f shell of a rare-earth ion taken into account (the LSDA + U). Spectral properties of these materials are studied by the optical ellipsometry method in the wavelength range of 0.22–16 μm. It is established that the optical absorption spectra are significantly modified upon partial substitution of nickel by copper atoms. The experimental dispersion dependences of optical conductivity in the region of interband light absorption are interpreted on the basis of calculations of electronic state densities.

Solvent effects on the spectroscopic, structural, and electronic properties of 8-hydroxy-2-quinolinecarboxylic acid (8HQC) were analyzed theoretically and experimentally. Density functional theory (DFT) B3LYP/6-311++G(d, p) used within polarized continuum model (PCM) to characterize the solvent effects in benzene, diethyl ether, ethanol, and water. Experimental FT-IR spectra in ethanolic and aqueous solutions were recorded and compared with solid phase experimental data. Nucleus independent chemical shifts were calculated as aromaticity indices. Our results show that the spectroscopic, structural, and electronic properties of 8HQC are solvent dependent.

Luminescence of Ca0.5Ba0.5Ga2S4 crystals activated by Eu2+ and Er3+ ions by B. G. Tagiev; O. B. Tagiev; T. G. Nagiev; S. G. Asadullaeva; M. S. Leonenya; G. P. Yablonskii; S. A. Abushov (389-392).
The photoluminescence (PL) in the visible spectral range of Ca0.5Ba0.5Ga2S4 solid solutions activated with ions of rare-earth elements Eu2+ and Er3+ has been studied in the temperature range of 10–300 K. The PL spectrum contains a strong luminescence band peaking at 530 nm, which is due to the 4f 65d → 4f 7 transitions in Eu2+ ions and weak lines in the range of 650–675 nm, which are due to the 4 F 9/24 I 15/2 transitions in Er3+ ions. The position of the PL spectrum and the total PL intensity are characterized by high temperature stability in the range of 10–300 K; the total PL intensity decreases by only 13% with respect to the maximum value at 10 K. The PL decay time and the activation energy of nonradiative recombination channels are found to be τ e = 291 ns and E a = 41 meV, respectively.

Luminescence self-quenching in praseodymium-doped double sodium-yttrium fluoride cubic crystals (Na0.4Y0.6F2.2:Pr3+) by A. M. Tkachuk; S. E. Ivanova; A. A. Mirzaeva; M. -F. Joubert; Y. Guyot (393-411).
Energy transfer processes between praseodymium dopant ions, which are responsible for the luminescence self-quenching in crystals Na0.4Y0.6F2.2:Pr3+ (NYF:Pr3+; Pr = 0.4–9%), have been investigated experimentally and theoretically. Using methods of kinetic spectroscopy with selective excitation, the praseodymium luminescence decay kinetics from the levels 3 P 0,1 and 1 D 2 selectively excited by nanosecond laser pulses has been studied. Based on model quantum-mechanical calculations, interionic interaction microparameters have been determined theoretically and mechanisms that are responsible for the interaction of praseodymium ions by particular most likely energy transfer schemes have been elucidated. Energy transfer macrorates (of migration and quenching) have been found, and the values obtained have been used as parameters for calculation of the decay dynamics of the excited 1 D 2 and 3 P 0,1 levels of praseodymium ions. It has been shown that luminescence self-quenching from the 1 D 2 level in NYF:Pr3+ crystals can be described well in terms of the model of static ordered decay in the presence of dipole-dipole and dipole-quadrupole interactions. The luminescence self-quenching from the 3 P 0,1 levels is mainly determined by the dipole-dipole interaction, and it also can be described in terms of the model of the static ordered decay. Good agreement has been obtained between experimental and calculated kinetic dependences that characterize energy transfer processes in NYF:Pr3+ crystals in relation to the concentration of doping ions. Based on the obtained data, it has been concluded that investigated crystals of a certain composition are promising for use in quantum electronics and optical converters.

Comparative studies of singlet oxygen generation by fullerenes and single- and multilayer carbon nanotubes in aqueous suspensions by I. V. Bagrov; V. M. Kiselev; I. M. Kislyakov; A. M. Starodubtsev; A. N. Burchinov (412-416).
Singlet oxygen generation is studied in three types of carbon nanoparticles (C60 fullerene and single- and multilayer carbon nanotubes in the form of aqueous suspensions obtained by sonication) upon their irradiation by continuous-wave broadband visible radiation of light-emitting diodes.

Comparative studies of singlet oxygen generation by fullerenes and single- and multilayer carbon nanotubes in the form of solid-phase film coatings by I. V. Bagrov; V. M. Kiselev; I. M. Kislyakov; A. M. Starodubtsev; A. N. Burchinov (417-424).
Four types of carbon nanoparticles: C60 fullerene (crystalline and amorphized) and single- and multilayer carbon nanotubes were studied in the form of solid-phase film coatings for the purpose of obtaining singlet oxygen generation in the process of irradiation of these materials by continuous-wave broadband light-emitting diodes in the visible region spectra and by a monopulse 532-nm neodymium laser.

The effect of electron recombination processes on the luminescence kinetics of ZnO ceramics by K. A. Chernenko; L. Grigor’eva; E. I. Gorokhova; P. A. Rodnyi (425-430).
We have examined spectral and kinetic properties of photoluminescence of zinc oxide ceramics. Ceramics with and without addition of gallium have been studied. In the photoluminescence spectrum, we have observed two luminescence bands with maxima at 377–379 (near-band-edge luminescence) and 490 nm (green luminescence). It has been shown that the decay curves of the green luminescence are determined by two processes with different time and temperature properties, as well as the kinetics of release of carriers from electron traps. The relations between luminescence decay curves and mechanisms of luminescence excitation, as well as energy transfer processes, have been discussed.

Spectral properties of powder preparations of cadmium telluride and cadmium selenide with controlled nonstoichiometry by A. V. Khomyakov; E. N. Mozhevitina; V. V. Kuz’min; N. A. Kon’kova; I. Ch. Avetissov (431-434).
The reflection spectra of powder preparations of cadmium telluride and cadmium selenide with different contents of overstoichiometric components have been investigated in the range of 800–1700 nm. The reflectance is found to be maximum for samples with compositions close to stoichiometric. An increase in the concentration of overstoichiometric cadmium more radically reduces the reflectance in comparison with preparations containing excess chalcogen. It is shown that halftone images in the near-IR range can be formed by using of these materials.

Filtration of photon noises by a nonlinear interferometer by A. V. Belinsky; E. S. Markina (435-444).
Images formed by light exhibiting suppressed photon fluctuations represent an interesting object of investigation from the point of view of increasing the limiting information capacity of devices. Light with such properties can be prepared in a cavity filled by a nonlinear medium, in which light experiences self-phase modulation. Multimode light beams are studied and spatial frequency spectra of suppressed photon fluctuations are obtained. Efficient operating regimes of the system are found.

The extended boundary condition method (EBCM) in solving the electrostatic problem for axisymmetric Chebyshev particles the surface of which is described by the equation r(θ) = a(1 + ɛcosnθ) is studied. The main attention is paid to the case n = 1. The problem is reduced to solving infinite systems of linear algebraic equations (ISLAEs) for expansion coefficients of internal and “scattered” fields in terms of a spherical basis where matrix elements of the fields are integrals of products of Legendre functions and power functions. Radii of convergence R 2 and R 1 of these expansions, respectively, have been found analytically. For the considered particles, depending on perturbation parameter ɛ, conditions of the applicability of the EBCM have been obtained, i.e., conditions of correct construction of the T matrix (R 1 < R 2), as well as conditions of the validity of the external (R 1 < minr(θ)) and internal (R 2 > maxr(θ)) Rayleigh hypotheses under which expansions of the “scattered” and internal fields in terms of the spherical basis converge up to the surface of the particle beyond and inside it, respectively. In the particular case n = 1, numerical calculations have been performed; in this process, integral ISLAE elements have been represented as finite sums the summands of which depend on gamma functions. Calculations of matrix elements by explicit formulas have made it possible to considerably increase the dimension of the solved reduced ISLAE with preservation of the necessary accuracy. Analysis of results of numerical calculations verified their agreement with theoretical conclusions.

Results of retrieval of size and shape distributions of particles of a dispersive medium using measured data on the scattering matrix of aqueous suspensions of titanium oxide and barium titanate are given. Retrieval of the distributions has been performed by solving the optimization problem for the sum of squared deviations of experimental values of matrix elements and their values calculated using the model of spheroidal scatterers. It has been shown that the particle size distribution is retrieved more accurately upon minimizing the sum of squared deviations for the sum of diagonal elements, while the more accurate shape distribution (ratio of dimensions) is obtained upon minimizing the sum of squared deviations only for the element F 11.

A technique of Fourier holograms synthesis intended for use as spatial-frequency filters in dispersive correlators is considered. Expressions relating the spatial and spectral characteristics of the reference object, Fourier-hologram parameters, and geometric parameters of the system, which are necessary to synthesize holograms for a single-objective correlator, are obtained. Experiments on object images reconstruction using fabricated holograms and correlation signals formation in a dispersive correlator have been performed.

We have studied the effects of the laser fluence on the characteristics of Al nanoparticles produced by pulsed laser ablation of Al plate in deionized water without using surfactant. Five samples of aluminum nanoparticles were synthesized by nanosecond pulsed laser ablation of a high purity aluminum plate in distilled water at five different fluences in the range of 1–3 J/cm2. There is threshold fluence of the laser at which absorption of laser energy by water rises significantly. Absorption of the laser energy by water leads to increase oxygen atoms in the ablation medium and formation of aluminum oxide nanoparticles. By increasing the laser fluence below the threshold magnitude size of produced nanoparticles increase while by increasing the laser fluence above the threshold magnitude size of produced nanoparticles decrease. The UV-Visible-NIR absorption spectra of nanoparticles exhibit surface plasmon resonance absorption peak in the ultraviolet region. TEM and SEM micrographs are used to characterize the produced nanoparticles. The production rate of nanoparticles is increased with increasing the laser fluence.

Design, analysis and construction of an LDA optical setup using conventional as well as compact two hololens imaging system have been performed. Fringes formed at measurement volume by both the imaging systems have been recorded. After experimentally analyzing these fringes, it is found that fringes obtained using compact two hololens imaging system get improved both qualitatively and quantitatively compared to that obtained using conventional imaging system. Hence it is concluded that use of the compact two hololens imaging system for making LDA optical setup is a better choice over the conventional one.

In the present study we have observed and analyzed the fluorescence changes in the fluorescence spectra of four different samples like brilliant sulphaflanine, quinine bisulphate, coumarine 120 and porcine cornea and sclera including the changes in fluorescence spectrum of cornea are also observed after CO2 laser exposure. The preliminary study clearly explains the proof of concept only.

The effect of IR-laser irradiation on adipose tissue sensitized by indocyanine green is studied in vitro. Experiments and statistical analysis are used to show that wavelength-selective irradiation leads to an increase in the homogeneity of optical images of adipose cells with time. The transmission coefficient that is averaged over the image area weakly depends on the observation time. An increase in the homogeneity of images is interpreted as a result of immersion of optical inhomogeneities of tissue owing to the intracellular liquid that is released through the photochemically induced pores in cellular membranes. An increase in the optical homogeneity of the medium is compensated for by a decrease in the transmission coefficient of the sensitizer, which is manifested as a weak time dependence of the image-averaged transmittance of tissue.