Optics and Spectroscopy (v.119, #1)

Specific features of application of the Hartree-Fock method with the orthogonality restrictions proposed earlier (V. N. Glushkov, Chem. Phys. Lett. 287, 189 (1998)) to calculations of energies of highly excited electronic states of the same symmetry are studied. Different schemes are discussed that allow one to avoid the variational collapse in constructing determinant wave functions for excited states. The accuracy of the method is demonstrated for the example of calculation of more than 30 excited states of He and Li atoms.

Diagnostics of Zinc-Selenium plasma produced by Nd:YAG laser by M. Hanif; M. Salik; F. Arif (7-15).
We present the optical emission studies of the Zinc-Selenium (Zn-Se) plasma produced by the first (1064 nm) and second (532 nm) harmonics of a Q-switched Nd:YAG laser. The target material was placed in front of laser beam in air at atmospheric pressure. The experimentally observed line profiles of neutral zinc (Zn I) at 249.34, 256.77, 271.24 and 277.09 nm respectively have been used to extract the electron temperature using the Boltzmann plot method. Whereas, the electron number density has been determined from the Stark broadening method using the neutral zinc (Zn I) line at 481.05 nm. The electron temperature is calculated by varying the distance from the target surface along the line of propagation of plasma plume and also by varying the laser irradiance. Beside we have studied the variation of number density as a function of laser irradiance as well as its variation with distance from the target surface. It is observed that electron temperature and electron number density increases as laser energy is increased.

The influence of isotopic substitution on the values of the effective dipole moment parameters of the q 0 J, qJ, q 2 J, and q 3 J types has been studied for carbon dioxide bands, which are active only in the case of asymmetric isotopologues of this molecule. It has been shown that the effective dipole moment parameters for these bands strongly depend on the mass difference of the oxygen atoms entering into the molecule composition.

The kinetics of the luminescence concentration depolarization of molecules in a medium is studied theoretically. It is shown that the concentration depolarization kinetics is well described by a stretched exponential function of time, r(t)/r 0 ≈ exp[−b(t/τ)β], where r(t) and r 0 are the luminescence anisotropy values at time moments t and t = 0, respectively. The parameters b and β allow the determinnation of the penetration depth of the molecules in the medium.

We have studied exchange processes in contact complexes of triplet eosin molecules with oxygen molecules in the triplet (3Σ g ) and singlet (1Δ g ) states in thin polyvinylbutyral films in the presence of gold nanoparticles. Upon resonant excitation of surface plasmons in gold nanoparticles into the absorption band of eosin molecules-singlet oxygen sensitizers-we have obtained an increase in the intensity of the delayed fluorescence and an increase in the lifetime of the dye with simultaneous quenching of the luminescence of singlet oxygen. The kinetics of the delayed fluorescence of the dye as a result of singlet-triplet annihilation of triplet eosin molecules with singlet oxygen molecules has been investigated. To compare theoretical and experimental data, we have numerically simulated energy transfer processes. Rate constants of energy transfer and of singlet-triplet annihilation, as well as quenching constants of triplet states of the dye by molecular oxygen, have been calculated. Luminescence quantum yield 1Δ g of polyvinylbutyral has been estimated. We have analyzed quantum-chemically electronic mechanisms of singlet-triplet annihilation of oxygen and eosin.

Fluorescent properties of merocyanines based on 1,3-indandione by A. V. Kulinich; E. K. Mikitenko; A. A. Ishchenko (39-48).
We have studied the fluorescent properties of vinylogous series of merocyanine dyes based on 1,3-indandione and heterocycles of different electron-donating powers. Using a set of solvents with polarities lying in a wide range, we have analyzed the dependence of their solvatofluorochromism on the key structural parameters—the donor heterocyclic group and the length of the polymethine chain. It has been found that the signs of solvatochromism and solvatofluorochromism of merocyanines under study coincide. However, the solvent more weakly affects the position and the shape of their fluorescence bands than in the case of absorption spectra, especially, for negatively solvatochromic derivatives of 1,3-diphenylbenzimidazole. We have found that, upon passage from polar aprotic solvents to alcohols, the fluorescence quantum yields of dyes under investigation (irrespective of the sign of their solvatochromism) decrease. We have performed quantum-chemical calculations of merocyanine molecules by the DFT/B3LYP/6-31G(d,p) and TDDFT methods, including calculations taking into account the polarity of the medium by the PCM method. Based on the analysis of electronic transitions, we have explained the fluorescence quenching of indandione merocyanines in alcohol, which is unusual for carbonyl-containing intraionic dyes.

The dynamic of network of self-assembled liposome by end-capped polymer was investigated using dynamic light scattering. The liposome network, physically cross-linked by mixed liposome solutions with three different length scale of cholesterol end-capped polyethylene glycol. The network of liposome is dependent on both the polymer concentration and length scale. In the pure liposome, one motion at low time scale is observed by DLS. In the higher concentration of polymer in liposome, several motion is observed that the fast motion is alpha relaxation and other two slow motion are beta and gamma relaxations. The distance between diffusion coefficient of fast and slow relaxation is increased with increase of length scale of endcapped polymers. The SAXS data is fitted with a Percus-Yevick hard sphere model and it shows that the size of liposome increasing with increase of polymer length scale in the mixture system.

Using tellurium(IV) complex compounds with outer-sphere ammonium cations as an example, we have studied the interrelation between their geometric structure and spectral-luminescent properties. In the series of compounds of tellurium(IV), which are characterized by the island octahedral coordination of Te(IV) ions, the luminescence intensity has been found to depend on the degree of distortion of the coordination polyhedron of the Te(IV) ion, the position of the A band in diffuse reflection spectra, and the energy of the luminescence transition 3 P 11 S 0 of the tellurium(IV) ion. We have revealed that the considered Te(IV) complexes possess reversible thermochromic properties.

New Sm(III) complexes as electronic-excitation donors of the Seta-632 squaraine dye by A. V. Egorova; I. I. Leonenko; D. I. Aleksandrova; Yu. V. Skripinets; V. P. Antonovich; E. N. Obukhova; L. D. Patsenker (59-65).
We have found optimal formation conditions of new Sm(III) chelate complexes with derivatives of oxoquinolinecarboxylic acid (L 1 and L 2) and determined their spectral-luminescent characteristics (the luminescence and luminescence excitation wavelength maxima and the luminescence lifetimes). We have revealed that the Seta-632 squaraine dye (a fluorescent label of proteins and other biological molecules) quenches the luminescence of complexes Sm(III)-L 1 and Sm(III)-L 2. The quenching of chelate complexes is caused by the Förster resonant electronic-excitation energy transfer (FRET) from the donor (Sm(III)-L 1 or Sm(III)-L 2) to the acceptor (Seta-632). In this case, the luminescence intensity of the Seta-632 dye in the presence of Sm(III)-L 1 and Sm(III)-L 2 increases by factors of 64 and 27, respectively. The values of the Förster radii (R 0(Sm-L1) = 38 Å, R 0(Sm-L2) = 35 Å) and the overlap integrals of the luminescence spectra of the two energy donors with the absorption spectrum of the acceptor (J Sm-L1 = 1.22 × 1012 M−1 cm−1 nm4 and J Sm-L2 = 1.06 × 1012 M−1 cm−1 nm4), which have been calculated from the luminescence quantum intensity of the donors and from the absorption spectrum of the acceptor and its molar absorption coefficient, have made it possible to characterize the Seta-632 dye as an efficient quencher of the luminescence of Sm(III) ions. We are the first to propose Sm(III)-L 1 and Sm(III)-L 2 chelate complexes as FRET donors.

The spectral properties of a one-dimensional photonic crystal (PC) with a structure defect (a layer of isotropic nanocomposite inserted between two multilayer dielectric mirrors) have been investigated. The nanocomposite consists of spherical gold nanoparticles dispersed in a transparent matrix; it is characterized by effective resonant permittivity. The dependence of the transmission and absorption spectra on the size and concentration of nanoparticles is analyzed. It is shown that the transmission spectrum contains, along with the band gap caused by Bragg diffraction of light, an additional nontransmission band due to the nanocomposite absorption near the resonant frequency.

Using the example of europium and terbium complexes with acyl-2-aminobenzoic acids, it is shown that the nonradiative losses of excitation energy in solutions of water-soluble polymers can be decreased both due to the coordination of lanthanide ions with oxygen-containing functional groups of polymers and due to the viscosity formed by them, which reduces molecular diffusion.

We have compared the fluorescence intensity of 2-naphthoyltrifluoroacetonate (NTA) in nanoparticles from Gd(NTA)3phen complexes with the fluorescence intensities of this compound in nanoparticles from similar complexes of Pr, Nd, Sm, Eu, Tb, Dy, Er, Ho, and Tm, which absorb in the NTA fluorescence range. We have proven that there is energy transfer from the S 1 level of NTA ligands to Ln(III) ions, which occurs with rates k tr ∼ 1011–1012 s−1. We have also studied the competition between two processes: energy transfer from Ln(NTA)3phen to Ln(III) ions and energy transfer to Nile blue molecules incorporated into nanoparticles from complexes of these ions. It has been shown that, in nanoparticles from complexes of Nd(III), Tb(III), Dy(III), and Tm(III) ions, which are incapable of sensitizing the fluorescence of Nile blue, the values of k tr2 for the energy transfer from NTA to Ln(III) ions, which were obtained from the data on the change in the intensity of the sensitized fluorescence of Nile blue, completely coincide with the values of k tr1 determined from the fluorescence quenching of NTA in these nanoparticles. We have found that, in nanoparticles from Pr, Sm, Eu, Er, and Ho complexes, the efficiency of the sensitized fluorescence of Nile blue is higher than that predicted from the fluorescence quenching of NTA by these ions in their complexes, which indicates that all these ions participate as mediators in the energy transfer from ligands to the dye.

Laser-induced luminescence in hybrid nanofilms by R. R. Saifutyarov; A. V. Khomyakov; A. A. Akkuzina; R. I. Avetisov; O. B. Petrova; I. Kh. Avetisov; S. V. Kravchenko (84-88).
Tris(8-hydroxyquinoline) boron (Bq3) was synthesized by a high-temperature exchange reaction. Bq3 powders containing various polymorphous modifications were synthesized, and their photoluminescent characteristics were analyzed. Films of Alq3/B2O3/Al hybrid materials (HMs) were deposited on glass substrates by vacuum thermal evaporation. It is shown that local heating by a diode laser (785 nm) with an intensity of 150 W/cm2 for one second causes irreversible transformation in the HM film structure. The chromaticity coordinates of the photoluminescence of laser-irradiated regions considerably differ from those of the initial HM film luminescence.

Parametric field excitation in a cavity with oscillating mirrors by N. N. Rosanov; A. A. Matskovskii; V. L. Malevich; G. V. Sinitsyn (89-91).
The dynamics of the parametric excitation of an electromagnetic field in a cavity that is composed of two plane mirrors has been analyzed. One of the mirrors is immobile and has a finite reflectance spectral band, while the other mirror is oscillating with a wider spectral band. The field energy in the cavity may increase due to a transfer from the kinetic energy of the mirrors. Estimates and calculation results for a Lorentz profile of the spectral band of the reflectance show that, under conditions of a parametric resonance, the initial exponential increase in the field energy in the cavity is stopped and the stable pulse-periodic mode is formed.

Quantum Hamiltonian theory of an electro-optical modulator by G. P. Miroshnichenko; A. V. Gleim (92-97).
A Quantum Hamiltonian formalism is proposed for the description of an electro-optical modulator based on the linear Pockels effect. Optical photons interact with photons of a microwave mode in a combined high-Q cavity made of a LiNbO3 crystal. The microwave photons occupy a coherent state, while optical photons have an arbitrary density matrix. The spectrum of a photodetected modulated signal is analyzed as a function of the frequency of a tunable optical filter. Numerical estimates are obtained, and quantum effects in the spectrum, such as the red shift of the central frequency and sidebands, the possibility of modulation of the optical signal by the microwave field vacuum, and the asymmetry of the intensity of the spectral sidebands, are discussed.

Demonstrating the possibility of implementing the Toffoli gate in crystals doped by rare-earth metal ions by R. A. Akhmedzhanov; L. A. Gushchin; I. V. Zelensky; Yu. P. Malakyan; D. A. Sobgaida (98-102).
A scheme for the implementation of the Toffoli gate in inorganic crystals doped by rare-earth metal ions is proposed. A numerical analysis of the factors affecting the fidelity of the Toffoli gate implementation is carried out, and estimates for the available experimental parameters are obtained. A demonstration experiment is set up in which behavior similar to the Toffoli gate is shown for ensembles of Pr3+ ions doped into a LaF3 crystal.

A problem of the relationship of phenomenological optical parameters of dispersive medium that contains inclusions with arbitrary shape and the parameters of such inclusions is theoretically solved in the approximation of 1D scattering phase function. It is demonstrated that the desired relationships can be represented in terms of several correction coefficients. In the presence of local inclusions, the scattering and absorption coefficients of the medium generally decrease relative to the corresponding coefficients of the uniform spatial distribution of the same amount of the dispersive material. Under certain conditions, an increase in the forward scattering of the medium with an increase in the size of inclusions can be obtained. Physical reasons for such a behavior of the phenomenological parameters are discussed, and analytical expressions for the above relationships are derived. The theoretical expressions are applied in various problems of biomedical optics in which optical characteristics of multicomponent biological tissues must be determined using the known spectral and geometrical characteristics of components. The results can be used by researchers who study light scattering in various natural and artificial media (e.g., biological tissues and sea water) that contain local scattering inclusions.

We demonstrate the possibility of obtaining information on small-scale inhomogeneities of the surface of a dielectric, which are caused by natural variation of the surface-layer polarizability and fluctuations of surface properties, by means of refraction of a plane electromagnetic wave under the condition of total internal reflection.

Optical properties of nanostructured gold-silver films formed by deposition of small colloid drops by A. A. Antipov; S. M. Arakelyan; T. A. Vartanyan; T. E. Itina; S. V. Kutrovskaya; A. O. Kucherik; I. V. Sapegina (119-123).
The formation of gold-silver cluster structures on surfaces of glasses has been investigated. The properties of these structures are analyzed in dependence on the weight ratio of metal nanoparticles and the particle concentration in the colloid. It is shown that the optical properties of these structures may change significantly with a change in the morphological properties and chemical composition of the structures.

Absolute stability of dynamic cavities by N. N. Rosanov (124-127).
The field structure in a cavity composed of an oscillating plane mirror and an immobile spherical mirror has been analyzed within the paraxial approximation. Relations between the radius of curvature of the spherical mirror and the distance between the mirrors at which the initially paraxial beam remains paraxial after multiple propagations through the cavity have been determined. It is shown that the stability is absolute, in contrast to the case of a static cavity (with immobile mirrors); i.e., deviations from the axial direction decrease exponentially with time.

Interaction of a Gaussian pulse with a one-dimensional photonic crystal by Yu. F. Nasedkina; S. V. Eliseeva; D. I. Sementsov (128-134).
A computer analysis of the profiles of reflected pulses and pulses passed through a photonic-crystalline medium has been performed. The time shift of the frequency component and its influence on the general pattern of signal distortion have been investigated. It is shown that the profiles of reflected and transmitted pulses are distorted even when they are normally incident on a defect-free one-dimensional photonic crystal. Distortions of the pulse profiles at the boundaries of the forbidden band of the photonic-crystal spectrum are most significant.

The set of equations governing the dynamics of the parameters of a super-Gaussian pulse propagating in an isotropic dielectric in regions of both normal and anomalous group velocity dispersion is obtained. It is demonstrated that stimulated Raman scattering can suppress the formation of a nonlinear focus. The expression for critical power of the signal for which self-focusing can still be compensated by diffraction-limited divergence is derived.

A beam splitter with a two-layer metal-dielectric structure in a Michelson interferometer is considered. It is shown that introduction of an additional dielectric interference layer makes it possible to reduce significantly (in comparison with a beam splitter with one metal layer) the difference in the reflectance from the side of air, the reflectance from the side of substrate, and the transmittance for p-polarized light, with conservation of a 90° phase shift for two outputs.

Spectral analysis is performed of the effective refractive index and the power transfer coefficient for a waveguide mode propagating from a three-layer to a four-layer planar structure with a high-refractive-index upper layer. Conditions of both optimal and extreme coupling of the three- and four-layer regions of the structure are considered depending on the wavelength. A spectral method of detection of extreme regions is proposed.

A Fourier holography scheme in a ring cavity with two Fourier holograms (a matched hologram and a hologram in the correlation plane) has been considered. The dissipation factor of the scheme is determined, and the influence of the hologram recording conditions and the additional filtering caused by the nonlinearity of the exposure characteristics of holographic recording media on this parameter is demonstrated. It is also shown that high-frequency filtering on holograms reduces the convergence rate of the system to the stable state, whereas low-frequency filtering accelerates convergence. In the case of ultrahigh-frequency filtering or rejection of low frequencies, which destroys the internal correlatedness of images processed, the lateral maxima of the dissipation term grow. As result, under these filtering conditions, the dynamics of the system includes two successive stages: divergent (or pseudorandom) and convergent, in which the scheme converges to stable formation of image, which was absent during hologram recording. The results of numerical modeling for a number of models of hologram recording and additional filterings on holograms are presented.

A way to construct a holographic indicator of the position of the central axis of a distant object based on recording a transmission hologram in a layer of photosensitive material and forming a remote real image before a light source is considered. A light source with a holographically formed marker designed for visual guidance to the object axis; it can be used to simplify aircraft landing on a glide path, preliminary visual alignment of large coaxial details of various machines, etc. Specific features of the scheme of recording a holographic marker and the reconstruction of its image are considered. The possibility of forming a remote holographic image marker, which can be aligned with a simultaneously operating reference laser system for determining the direction to an object and its optical axis, has been demonstrated experimentally.

A novel ultrawideband (UWB) monocycle pulse generation system by modulating a polarization modulator (PolM) with a low speed electrical nonreturn-to-zero (NRZ) signal is proposed, which significantly reduce the bandwidth requirement of the driving signal. At each bit transition of the input NRZ signal, two polarity-reversed Gaussian pulses are generated. By properly setting the delay between these two Gaussian pulses, an optical UWB monocycle pulse can be generated. Biphase modulation (BPM) can be realized by electrically switching the polarization direction at the output of PolM, if an electrically tunable arbitrary wave plate (AWP) is employed.

The effect of pathological processes on absorption and scattering spectra of samples of bile and pancreatic juice by K. M. Giraev; N. A. Ashurbekov; M. A. Magomedov; A. A. Murtazaeva; R. T. Medzhidov (162-170).
Spectra of optical transmission coefficients and optical reflectance for bile and pancreatic juice samples were measured experimentally for different forms of pathologies of the pancreas within the range of 250–2500 nm. The absorption and scattering spectra, as well as the spectrum of the anisotropy factor of scattering, were determined based on the results obtained using the reverse Monte Carlo method. The surface morphology for the corresponding samples of the biological media was studied employing electron microscopy. The dynamics of the optical properties of the biological media was determined depending on the stage of the pathology. It has been demonstrated that the results of the study presented are in a good agreement with pathophysiological data and could supplement and broaden the results of conventional methods for diagnostics of the pancreas.