Optics and Spectroscopy (v.106, #1)

The theory outlined in the first part of the study is applied to an analysis of self-broadening and broadening by foreign gases of spectral lines for a number of symmetric top molecules with a high potential barrier to the inversion vibration. In all cases considered, the results obtained are in better agreement with the experimental data than previous theoretical results; however, in some cases, the discrepancy is rather large. Possible reasons are discussed and the acute need for experimental data obtained with modern equipment is noted.
Keywords: 33.70.Jg

The spectral and power characteristics of radiation of the second positive system of nitrogen (C 3Π u B 3Π g ) in Ar-N2 and Ar-N2-Cl2 mixtures excited by barrier discharge have been studied experimentally. Addition of argon to N2 increased the radiation power by sixfold. In the triple mixture Ar-N2-Cl2 = 210/0.5/0.005, minor chlorine additions increased the intensity of the C 3Π u B 3Π g transition by 26% compared to Ar-N2 mixtures. Radiation power density of 2.7 mW/cm2 has been achieved. In both binary and triple mixtures, the second positive system of nitrogen was the major contributor to radiation, while the contributions of the fourth positive system of N 2 * (D 3Σ u +B 3Π g ), the Vegard-Kaplan transition of N 2 * (A 3Σ u +X 1Σ g + ), and the D′ → A′ band of Cl 2 * were negligibly small.
Keywords: 52.80.Tn; 42.72.Bj; 32.30.Jc

The temperature dependences of oxygen quenching rate constants of singlet ( $$ k_S^{O_2 } $$ ) and triplet ( $$ k_T^{O_2 } $$ ) states, as well as of the fractions of singlet ( $$ q_S^{O_2 } $$ ) and triplet ( $$ q_T^{O_2 } $$ ) states quenched by oxygen in vapor pahse of polycyclic aromatic hydrocarbons (PAHs), namely, anthracene, 2-aminoanthracene, 9-methylanthracene, 9,10-dibromoanthracene, chrysene, phenanthrene, fluoranthene, and carbazole, are studied. It is found that in the temperature range 433–673 K, the oxygen quenching rate constants of polycyclic aromatic hydrocarbons either do not change or slightly decrease with increasing temperature. The quenching activation energies E a for these cases are determined. The effect of the stored vibrational energy and the free energy of electron transfer from a PAH to oxygen on the temperature dependences of $$ k_S^{O_2 } $$ and $$ k_T^{O_2 } $$ is considered. The role played by charge-transfer complexes in the observed temperature dependences $$ k_S^{O_2 } $$ of and $$ k_T^{O_2 } $$ , as well as the applicability of a model of electron transfer concerted with reorganization of reactants for description of quenching in heated vapors is discussed.
Keywords: 32.50.+d; 33.50.Hv

A two-fraction model that makes it possible to analytically calculate the complex dielectric permittivity of liquid water in wide frequency and temperature ranges is described. The far IR spectrum of water is found as a dielectric response of vibrating H2O monomers and dimers, while the spectrum of low-frequency (Debye) relaxation is found as a response of collective reorientations of associated water molecules. It is shown that the dielectric spectra of water calculated at −5.6, 27, and 81.4°C agree well with its experimental spectra. The low-frequency Raman spectrum of water is calculated for the same set of model parameters as the spectrum of the complex dielectric permittivity. These spectra are found to correlate with each other, and the physical nature of the difference between them is clarified. An interpretation of the well-known anomaly of water at a temperature of T = 300 K is presented. It is shown that the number of water molecules that compose an associate at this temperature is minimal.
Keywords: 61.20.Gy; 61.20.Og; 77.22.Gm; 78.30.Cp

The specific features of defect modes of chiral photonic crystals with an anisotropic defect have been investigated. Peculiarities of the spectra of polarization observables of the system under consideration are analyzed at different thicknesses of the defect layer. It is shown that single refraction occurs in a defect mode, even though the system is anisotropic and inhomogeneous. We also investigated the specific features of the spectra of the photon density of states, light intensity at the defect center, and the Q factor of defect modes at different thicknesses of the defect layer and chiral photonic crystals. It is shown that the lasing wavelength of chiral photonic crystals with an anisotropic defect enriched in laser dyes (resonant atoms) can be controlled in a different way: by varying the defect layer thickness. It is shown that this system can operate as a narrow-band filter (mirror) with a controlled frequency width and location of the total transmission (reflection) range on the frequency scale.
Keywords: 42.70.Df; 42.79.Kr

Electrooptic properties of aqueous suspensions of nanotubes based on magnesium hydrosilicate by V. V. Voitylov; A. V. Voitylov; E. N. Korytkova; V. P. Romanov; S. V. Ul’yanov; V. V. Gusarov (50-55).
Nanotubes suspended in a fluid medium have been investigated by the electrooptic method. This method is based on measuring the relative changes in the intensity of light transmitted through a suspension of nanotubes with application of an external electric field. The electrooptic effect (difference in these changes for transmitted light plane-polarized along the external field and perpendicularly to it) is analyzed. For aqueous suspensions of Mg3Si2O5(OH)4 nanotubes, the field and relaxation dependences of this effect are investigated. An analysis of the results obtained suggests that nanotubes, even when their concentration in water is low, form strong stable aggregates, which, however, can be elongated and enlarged under long-term action of strong rf fields.
Keywords: 78.20.Jq; 78.20.Bh; 78.67.Bf; 78.67.Ch; 82.70.-y; 83.80.Hj

The monitoring of variations in the luminescence intensity (I lum) of nanostructures of Eu(MBTA)3phen (MBTA is p-methoxybenzoyl trifluoroacetonate) complexes formed in aqueous solutions upon the introduction of anions is proposed as a method of analyzing the composition of Eu(III), Gd(III) and Lu(III) phosphate complexes in solutions with [PO 4 3− ] < [Ln]. It is found that low-lability binuclear complexes, which rearrange within an hour or longer, are formed in these solutions. It is shown that the lability of Ln(III) carbonate complexes exceeds the lability of Ln(III) complexes with PO 4 3− . An analysis of the dependence of I lum of the solution on the concentration of Eu(III) ions and on the time from the instant of the solution preparation shows that, in aqueous solutions where the concentration of anions is higher than the concentration of Ln(III) ions, nanostructures of Eu(III) phosphate and carbonate salts are formed in the range of Ln(III) concentrations 0.5–5 μM at concentrations of anions on the order of 10 μM and at concentrations of exceeding 100 μM. The rearrangement of these nanostructures to nanostructures of Eu(MBTA)3phen complexes is studied.
Keywords: 33.50.-j

Fluorescence of polystyrene microspheres during photochemical synthesis of gold nanoparticles by O. B. Svistunova; V. V. Gorbunova; T. B. Boitsova (67-71).
The results of investigation of the fluorescence of carboxylated polystyrene microspheres in the process of photochemical synthesis of gold nanoparticles are presented. The introduction of an aqueous solution of hydrogen tetrachloroaurate (III) into an unirradiated polymer dispersion causes a decay of the excimer fluorescence in polystyrene at 335 nm. UV irradiation (λexc = 254 nm) of polystyrene dispersions in the presence of AuCl 4 ions leads to the formation of metal particles, which occurs after an induction period and affects the polystyrene fluorescence.
Keywords: 78.67.Pt

Optical properties of the HfO2 − x N x and TiO2 − x N x films prepared by ion beam sputtering by V. V. Atuchin; V. N. Kruchinin; A. V. Kalinkin; V. Sh. Aliev; S. V. Rykhlitskiĭ; V. A. Shvets; E. V. Spesivtsev (72-77).
Optical characteristics of the HfO2 − x N x and TiO2 − x N x films obtained by reactive ion beam sputtering have been investigated by spectral ellipsometry. The chemical composition of the films was determined using X-ray photoelectron spectroscopy. The nitrogen content in the oxynitride films (determined by the N2/O2 ratio in the gas mixture during synthesis) reached ≈9 at % for TiO2 − x N x and ≈ 6 at % for HfO2 − x N x . It is found that the dispersion relations n(λ) and k(λ) for the TiO2 − x N x films change from those characteristic of titanium dioxide to those typical of titanium nitride with an increase in the nitrogen content from 0 to ≈9 at %. The optical parameters of the HfO2 − x N x films depend weakly on the nitrogen content in the range 0–6 at %.
Keywords: 78.20.-e

Luminescence of neodymium-doped yttria by V. V. Osipov; V. I. Solomonov; A. V. Spirina; M. G. Ivanov; A. N. Orlov (78-83).
Pulsed cathodoluminescence of Nd3+: Y2O3 nanopowders of the cubic and monoclinic phases and the ceramics synthesized from these nanopowders has been investigated in the spectral range 350–850 nm. It is found that the IR emission band of neodymium ions in the Nd3+: Y2O3 cubic phase is located at λ1 ≈ 825 nm. When there is a monoclinic phase admixture, two additional luminescence bands of Nd3+ arise in the spectrum at λ2 ≈ 750 nm and λ3 ≈ 720 nm. The emission spectrum of all Nd3+: Y2O3 materials also contains a wide intrinsic band of yttrium oxide at λ ≈ 485 nm; however, the presence of neodymium decreases the intensity of this band and increases the its structurization. It is suggested that the structure of this band in Nd3+: Y2O3 materials is mainly determined by local absorption (self-absorption) of neodymium ions.
Keywords: 78.40.Ha; 78.60.Hk

The spectra of the absorption coefficients of external radiation by basic chromophores of human skin, such as melanin, basic tissue, and blood (including oxy- and deoxyhemoglobin), are studied in the wavelength range of 300–1000 nm. For estimates, analytical methods of the theory of light transfer are used, which take into account the multilayer structure of a biological tissue, multiple light scattering in a medium, and multiple rereflections of radiation between layers. The calculated spectra are compared with the wavelength dependences of the absorption indices of these components available from the literature. It is shown that the spectral behaviors of the coefficients and indices of absorption strongly differ, which is related to the selectivity of the optical properties of a biological tissue. The possibilities of predicting the absorption coefficients of the skin components from the absorption coefficient of the entire skin measured under conditions of variation of its biophysical parameters (the volume concentrations of melanin and blood vessels) over a wide range are evaluated.
Keywords: 42.25.Fx; 42.62.Be

The dynamics of an ultrashort optical pulse in impurity-containing ferroelectrics with hydrogen bonds has been considered in terms of microscopic pseudospin formalism, which uses the approximation of unidirectional propagation without limitations on the pulse power. The effective equations for the electric field amplitude and ferroelectric polarization have been obtained and numerically solved. Quasi-soliton propagation modes of ultrashort optical pulses are revealed, and their dependences on the microscopic Hamiltonian parameters are analyzed.
Keywords: 42.70.Mp

The evolution of two-frequency solitons in an optical fiber with a longitudinally nonuniform nonlinearity by O. V. Matusevich; V. A. Trofimov; E. A. Yudina; B. A. Malomed (99-107).
The evolution of two-frequency solitons in an optical fiber, as well as the practically important special case of absence of the second-harmonic wave, in the presence of a longitudinal nonuniformity of the coefficients characterizing the propagation nonlinearity are considered. The solitons found for media with constant values of the nonlinearity coefficients are used as initial distributions for media with a periodic dependence of the nonlinearity coefficients on the longitudinal coordinate. Modulation of the coefficient of cubic or quadratic nonlinearity is shown to result in oscillations of the peak intensity of the solitons (in both their components if two-color solitons are considered). In the case of a weak modulation of the nonlinearity coefficients, oscillations of the peak intensity occur at the frequency coinciding with the frequency of modulation of the nonlinearity coefficients. Under the weak influence of a periodically modulated cubic nonlinearity, parameters of quadratic solitons also oscillate upon the propagation. Regions of stability of solitons in the space of the modulation parameters are established.
Keywords: 42.65.Tg

The influence of the periodic motion of a monochromatic light source on the observed spectrum of its radiation in the far-field and near-field zones is considered. The appearance of components shifted in frequency (harmonics of the oscillation frequency of the source) is demonstrated. The spatial structure of harmonics is investigated, and the presence of optical vortices in these harmonics is shown.
Keywords: 42.25.-p

The dependences of the degree of polarization of polychromatic radiation on the length of a single-mode optical fiber (SMF) with random inhomogeneities have been obtained by mathematical modeling. The case is considered where radiation having both polarization modes excited with equal weights of linear polarization is first introduced into a depolarizer of polychromatic radiation (a SMF segment with high linear birefringence) and arrives at an SMF with low linear birefringence. It is shown that the degree of polarization of radiation after transmission through the first segment becomes significantly suppressed and remains almost constant upon propagation through the second segment, after which it begins to sharply increase at some length; i.e., repolarization of radiation occurs. It is shown that repolarization of radiation depends weakly on the angle made by the axes of unperturbed linear birefringence of the first and second segments. The conditions for the length of the first segment (depolarizer) under which the degree of polarization remains minimum throughout the second segment are determined.
Keywords: 42.25.Dd; 42.25.Ja

The spatial dynamics of variations in the intensity of the luminescence of quantum systems in crystals of the medium and highest categories of symmetry upon excitation with opposing optical pulses of an arbitrary shape is investigated by numerical simulation methods. It is established that the material dispersion, which is responsible for the dispersion spreading of pulses, has no effect on the shape and width of the envelope of the spatial distribution of the luminescence intensity, as well as on the depth of the luminescence intensity modulation associated with the interference of opposing pulses.
Keywords: 42.25.Kb

A new method for the self-referencing measurement of the amplitude-phase shape of an ultrashort pulse is proposed. The method uses a two-frequency characteristic of the pulse, which is defined as S(F 1)S(F 2), where F is the frequency, S(F) is the complex Fourier spectrum of the pulse, and F 1 and F 2 are two independent variables. It is shown that this characteristic can be generated as a two-dimensional polychromatic light wave upon generation of the sum frequency of two crossed spectral decompositions of one and the same pulse, as well as upon space-time Fourier transform of radiation of the noncollinearly generated second harmonic of the pulse. In an orthogonal system of transverse coordinates F 1 + F 2 and F 1F 2, at any given value of F 1 + F 2, the radiation frequency of this wave in the direction of the second coordinate F 1F 2 does not change. Therefore, the phase structure of the two-frequency characteristic can be reconstructed by the standard method of lateral shear interferometry in the direction of this coordinate. In the reconstructed two-dimensional phase structure of the two-frequency characteristic, any section by the plane F 1 = const or F 2 = const yields the phase structure of the spectrum of the pulse under study. This makes it possible to reconstruct the amplitude-phase shape of the pulse.
Keywords: 42.65.Re

Optical properties of multilayer structures by M. S. Lebedev; B. M. Ayupov; T. P. Smirnova (139-141).
The possibility of using the ellipsometry method for investigation of the optical properties of multilayer films and structures is shown. The optical properties of structures HfO2/SiO2/Si, HfO2/Si, ZrO2/Si, Ta2O5/Si, and Al2O3/Si are studied. It is found that a layer of hafnium silicate is formed at the interface between the HfO2 film and Si. Annealing of the structures in oxygen shows that oxides studied are oxygen-permeable and that the thickness of SiO2 at the film-substrate interface increases. The growth rate of SiO2 layers depends on the chemical nature of an oxide. Al2O3 films are impermeable for oxygen diffusion. The production of layers of alloys (Al2O3) x (HfO2)1 − x is optimized, which allows one to obtain layers with a homogeneous distribution of elements over the thickness.
Keywords: 78.67.Pt

The interaction of femtosecond pulses with surfaces of semiconductors accompanied by the appearance of different nanostructures and nanoholes is studied. The formation of nanostructures was observed for semiconductors placed into different media. The effect of different parameters (angle of incidence, light polarization, number of shots, pulse duration, etc.) on the formation of the structures is analyzed. The period of the arising ordered structures could be either on the order of the light wavelength (700–800 nm) or much smaller (180 nm).
Keywords: 78.67.-n; 42.50.Vk; 78.40.Fy; 78.20.Nv

Birefringence in leucosapphire products upon oblique incidence of rays by V. N. Vetrov; B. A. Ignatenkov (147-151).
Formulas are derived for calculating the refractive index of an extraordinary ray for hemispherical shells fabricated from leucosapphire and its textured analog. These formulas make it possible to determine the local birefringence and the direction of propagation of both rays after refraction on the surface of hemispherical shells and lenses. The influence of the geometry of the position of the optical indicatrix on the birefringence in leucosapphire products with a complex configuration is analyzed.
Keywords: 78.20.Fm