Optical anisotropy of uniformly aligned planar surfactant lyotropic nematic doped with hemoglobin. - ISSN 1609-1833

The system under study is a nematic phase of lyotropic surfactant liquid crystal, cetylpyridinium chloride/hexanol/brine. Optical birefringence measured for well-aligned surfactant nematic (surfonematic) is weakly dependent on the light wavelength within the studied spectral region (500 - 700 nm) and its absolute value is about <$E6~ times ~10 sup -4 }>. Doping of the surfonematic by hemoglobin (1,5 % by weight) does not affect the birefringence value, suggesting that the hemoglobin does not produce its own birefringence and does not affect the scalar orientational order parameter of the surfonematic matrix. The absorption coefficients of hemoglobin in the surfonematic matrix exhibit a broad band shifted several tens of nanometres towards longer wavelengths, when compareto the spectrum of hemoglobin dissolved in water. The latter indicates that the hemoglobin residues form molecular complexes with the surfactant molecules. Weak (~<$E2~ times ~10 sup -2>) linear dichroism of hemoglobin at the wavelengths corresponding to light absorptionby oxygen bonds gives the estimation of the orientational scalar order parameter of hemoglobin molecules in well-aligned surfonematic matrix (~<$E10 sup -2>).

On the problem of phase transitions in lysozyme crystals. - ISSN 1609-1833

We present experimental evidence of the fact that lysozyme crystals, which are grown from their mother solution and exist in it, dissolve on heating above <$ET~ symbol Ы ~307~ roman K>. We argue that the anomaly in the light scattering recently observed at the temperature T = 307 K and identified in the reference [Svanidze A.V. et al. 2006. JETP Lett. 84: 551] as a structural crystalline phase transition in the single lysozyme crystals, in fact, corresponds to a temperature limit of the crystal existence.

Optical extinction spectra of the aqueous suspensions of Ag nanoparticles. - ISSN 1609-1833

The experimental results on the extinction spectra of aqueous suspensions of silver nanoparticles are presented. It is shown that optical properties of suspensions are strongly affected by the size and shape of the particles. Extinction spectra of monodisperse Ag colloid consist of two characteristic bands centered at about 430 and 540 nm, which can be explained in terms of Mie theory. These bands arise from the excitation of dipole and quadrupole components of surface plasmon resonance respectively.Presence of rod-like particles in colloid leads to broadening and tailing of the dipole component of the extinction spectra.

Raman spectra and optical properties of thin <$Eroman bold {As sub 40 S sub 60 }> and <$Eroman bold {As sub 40 S sub 50 Se sub 10 }> films. - ISSN 1609-1833

Structure and optical properties of <$Eroman {As sub 40 S sub 60 }> and <$Eroman {As sub 40 S sub 50 Se sub 10 }> glasses and thin films have been studied using the Raman spectroscopy. The structure of the films is suggested to be basically formed by triangular <$Eroman AsS sub 3> and <$Eroman AsSe sub 3> pyramids linked by two-fold coordinated sulphur or selenium atoms. A considerable amount of structural units with homopolar As - As and S(Se) - S(Se) bonds has been found in the matrix of investigated compounds. The influence of illumination and annealing on the structure and optical properties of <$Eroman {As sub 40 S sub 60 }> and <$Eroman {As sub 40 S sub 50 Se sub 10 }> films has been studied. It has been shown that the mentioned actions lead to polymerization of molecular <$Eroman {As sub 4 S(Se) sub 4 }> groups and <$E{ roman S(Se)} sub n> chains in the film matrix and formation of structural units with heteropolar As - S and As - Se bonds. This is accompanied by the absorption edge shift towards the long-wavelength region and the increase in the refractive index.

Pancharatnam's phase induced by spin-orbit interaction in weakly guiding twisted elliptical fibres. - ISSN 1609-1833

We derive the expressions for l = 1 modes of weakly guiding twisted elliptical fibres and the polarization corrections to the scalar propagation constant of these modes in the framework of Jones matrix formalism in the re?ectionless approximation. Usingthese results, we demonstrate that the topological Pancharatnam's phase in the twisted elliptical fibre appears due to spin-orbit coupling in fibres and is absent in the scalar approximation.

Light-induced Freedericksz transition and optical multistability in nematic liquid crystals. - ISSN 1609-1833

We revisit the problem of light transmission through a slab of homeotropically oriented nematic liquid crystal and solve self-consistently a system of coupled nonlinear equations describing orientation of the nematic director in the slab and the Maxwell equation for the electric field. We demonstrate that optical transmission of the slab as a function of input power shows a multistable hysteresis-like behaviour. We suggest that this multistability can be useful for creating tunable all-optical switching devices based on the liquid-crystal infiltration of photonic crystals.

Dipole glassy state evidence for <$Ebold {{ roman СuInP sub 2 (Se} sub х { roman S} sub {1~-~х } ) sub 6 }> ferrielectric mixed crystals from Raman scattering and optical absorption data. - ISSN 1609-1833

The temperature and concentration dependences of Raman scattering and optical absorption spectra for <$E{ roman СuInP sub 2 (Se} sub х { roman S} sub {1~-~х } ) sub 6 > crystals are investigated. Similarly to dynamic disordering of <$Eroman Cu sup +> ions at the transition from ferrielectric into paraelectric phase for <$Eroman {CuInP sub 2 S sub 6 }> compound, static disordering of these ions in the mixed crystals in the dipole glassy state at low temperatures determines rise in the phonon damping and increase in the energetic width w of exponential optical absorption edge. The concentration and temperature dependences w(T,x) clearly reveal "asymmetry" of the dipole ordering on T - x phase diagram: the dipole glassy state smoothly evolves into ferrielectric one, coexisting with the latter under decrease of selenium content till x = 0. The dipole glassy state sharply transforms into ferrielectric phase with growing selenium concentration, passing through the relaxor state in the region of <$Ex~ symbol Ы ~0,7~-~0,8>.

Correlation- and singular-optical approaches in diagnostics of polarization inhomogeneity of coherent optical fields from biological tissues. - ISSN 1609-1833

The paper presents results related to the correlation structure of polarization images of biological tissues. The technique for measuring coordinate distribution of the degree of mutual polarization has been proposed. The topological (singular) description of polarization-inhomogeneous images of biological tissues has been analyzed. It has been shown that the average statistical size of the S-contour correlates with the half-width of autocorrelation function for the coordinate distribution of the mutual polarization degree.

Electrically and magnetically induced optical rotation in <$Eroman bold {Pb sub 5 Ge sub 3 O sub 11 :Cr}> crystals at the phase transition. 1. Electrogyration effect in <$Eroman bold {Pb sub 5 Ge sub 3 O sub 11 :Cr}>. - ISSN 1609-1833

We present the results of studies for temperature dependences of electrogyration (EG) effect and natural optical activity in <$Eroman {Pb sub 5 Ge sub 3 O sub 11 :Cr}> crystals. Extremely high magnitude of EG coefficient is found for these crystals. We also demonstrate how the Curie-Weiss constant, the critical exponents of the order parameter and the dielectric permittivity, as well as the coefficients of thermodynamic potential, could be derived from the temperature dependences of optical activity and EG coefficient.

Highly efficient acoustooptic diffraction in <$Eroman bold {Sn sub 2 P sub 2 S sub 6 }> crystals. - ISSN 1609-1833

We have studied the acoustooptic (AO) diffraction in <$Eroman {Sn sub 2 P sub 2 S sub 6 }> crystals and found that they manifest high values of AO figure of merit. The above crystals may therefore be used as highly efficient materials in different AO applications.

Electrically and magnetically induced optical rotation in <$Eroman bold {Pb sub 5 Ge sub 3 O sub 11 :Cr}> crystals at the phase transition. 2.Faraday effect in pure and Cr-doped lead germanate in the presence of electric field and spontaneous polarization. - ISSN 1609-1833

This work presents the results for the Faraday rotation in pure and Cr-doped lead germanate crystals studied in the course of proper ferroelectric phase transition. We show that the increment of the Faraday rotation appearing at the phase transition is caused by a combined magneto-electrooptic effect induced by spontaneous polarization. It is proportional to the square of spontaneous polarization. The phenomenon revealed by us corresponds to combined effects of crystal optics, which appear due to common action of different fields.

Studies of magnetogyration in cubic <$Eroman bold {Bi sub 12 GeO sub 20 }> crystals using small-angular magnetooptic polarimetry. - ISSN 1609-1833

We present the results of studies for magnetogyration (MG) effect in non-centrosymmetric, non-polar <$Eroman {Bi sub 12 GeO sub 20 }> crystals performed with the small-angular polarimetric mapping technique. The magnitude of MG rotation obtained with the small-angular mapping is close to the corresponding values obtained recently on the basis of single-ray polarimetry. Our results demonstrate that multiple reflections of light play a key role in the studies of MG effect in <$Eroman {Bi sub 12 GeO sub 20 }> crystals. They lead to the error, which is at least two times as large as the expected value of the MG rotation.

Separation of instant and accumulated nonlinear optical responses of dye-doped liquid crystal using Z-scan traces. - ISSN 1609-1833

A theoretical approach is developed for distinguishing between the instant nonlinear optical response and the photoinduced accumulation effect on the refractive index. This is performed in terms of superposition of different lens transparencies for the known Z-scan technique. For the case of homeotropic liquid 5CB crystal cell doped with anthraquinone dye, we prove a possibility for decomposing consequent irreversible Z-scan traces into the contribution of instant nonlinear optical response, which takes place before the reorientation threshold, and the accumulated photoinduced refractive index variations occurred due to the exposition.

On the "Forbidden" Ferroelastic Domain Structure in <$Ebold { roman Rb } sub 2x { roman Tl } sub {2(1~-~x) } roman {Cd sub 2 (SO sub 4 ) sub 3 }}> Crystals (x = 0,1, 0,2 and 0,3). Optical Microscopic Observations=Про "заборонену" сегнетоеластичну доменну структуру в кристалах <$Ebold { roman Rb } sub 2x { roman Tl } sub {2(1~-~x) } roman {Cd sub 2 (SO sub 4 ) sub 3 }}> Crystals (x = 0,1, 0,2 and 0,3). Оптико-мікроскопічні спостереження.. - ISSN 1609-1833

Ferroelastic (FE) domain structure and movement of phase boundaries have been studied in the course of phase transitions in <$Ebold { roman Rb } sub 2x { roman Tl } sub {2(1~-~x) } roman {Cd sub 2 (SO sub 4 ) sub 3 }}> crystals. The reasons for the appearance of so-called "forbidden" domain structure in FE langbeinites have been found. We have shown that two types of conjugated domain walls can appear. In some cases, the phase boundaries could play a part of domain walls.

Spectroscopy of Mn-Doped Glasses of CaO - <$Eroman bold {Ga sub 2 O sub 3 ~-~GeO sub 2 }> System. - ISSN 1609-1833

The EPR, UV and visible optical spectra of absorption, luminescence excitation and emission, as well as the luminescence kinetics of impurity <$Eroman Mn sup 2+> centres in Mn-doped glasses of CaO - <$Eroman {Ga sub 2 O sub 3 ~-~GeO sub 2 }> system have been measured and analysed. The EPR spectra ofas-synthesised Mn-doped glasses consist of three broad bands with the effective g-factors <$Eg sub eff ~ symbol <64> ~4.3>, 3,0 and 2.0. The observed spectra have been attributed to both the isolated <$Eroman Mn sup 2+> (<$E3d sup 5 ,~ nothing sup 6 S sub {5"/"2 }>) ions occupying octahedral sites and revealing a broad distribution of crystal field parameters, as well as small clusters of <$Eroman Mn sup 2+> ions. The optical spectroscopy has shown that the manganese impurity is incorporated into octahedral sites of CaO - <$Eroman {Ga sub 2 O sub 3 ~-~GeO sub 2 }> glass network as both <$Eroman Mn sup 2+> and <$Eroman Mn sup 3+> ions. The intense broad absorption band with the maximum near 460 nm is related to the spin-allowed <$Eroman { nothing sup 5 E sub g ~ symbol О ~ nothing sup 5 T sub 2g }> transition of <$Eroman Mn sup 3+> ions in trigonally distorted octahedral sites of CaO - <$Eroman {Ga sub 2 O sub 3 ~-~GeO sub 2 }> glass network. The weak spin-forbidden absorption lines of <$Eroman Mn sup 2+> ions have not been observed against the background of a strong absorption band of <$Eroman Mn sup 3+>. The observed luminescence band with the maximum in the vicinity of 650 nm is explained by <$Eroman {T sub 1g ~ symbol О ~ nothing sup 6 A sub 1g }> transition of <$Eroman Mn sup 2+> ions

occurring in trigonally distorted octahedral sites. The luminescence decay curve of <$Eroman Mn sup 2+> could be satisfactorily described within two-exponent approximation. The two different lifetimes (<$Etau sub 1 ~=~12.4~ roman ms> and <$Etau sub 2 ~=~3,98~ roman ms> at <$Elambda sub { roman exc }~=~300~ roman nm>) correspond to the two types of <$Eroman Mn sup 2+> centres with different local environments. A possible local structure of different <$Eroman Mn sup 2+> centres in CaO - <$Eroman {Ga sub 2 O sub 3 ~-~GeO sub 2 }> glass network is discussed.

Structure and Orbital Angular Momentum of Singular Array of Gaussian Beams. - ISSN 1609-1833

We consider theoretically and experimentally the structure and the orbital angular momentum (OAM) of the beam array consisting of aggregate of coherent fundamental Gaussian beams, whose axes are located on the surface of hyperboloid of revolution. An intrinsic characteristic of such the beam system is its OAM that cannot be eliminated by whatever transformations of the reference frame. This construction of the array enables one to change the OAM from zero up to very large values.

Luminescence and Reflection Spectra of <$Eroman bold {Sn sub 2 P sub 2 Se sub 6 }> Semiconductors-Ferroelectrics at Low Temperatures. - ISSN 1609-1833

We present the luminescence and reflection spectra of semiconductor-ferroelectric <$Eroman {Sn sub 2 P sub 2 Se sub 6 }> crystals obtained at T = 2K. It is found that the photo-excited luminescence has, most probably, exciton origin. The shape of the luminescence band indicates that the luminescence is presumably related to existence of excitons confined by inhomogeneous local field.

Optical Birefringence and Domain Structure of the as-Grown <$Ebold { roman Rb sub 2x roman Tl sub {2(1~-~x) } roman Cd sub 2 ( roman SO sub 4 ) sub 4 }> Solid Solutions at Phase Transitions. - ISSN 1609-1833

It is shown that the as-grown solid solutions <$Eroman Tl sub 2x roman Rb sub {2(1~-~x) } roman {Cd sub 2 (SO sub 4 ) sub 3 }> possess a residual optical birefringence in the cubic phase at room temperature. The existence of both the residual birefringence and the residual domain structure in the compound with x = 0,8 at the room temperature, along with the domain walls orientation and the orientation of extinction positions of the neighbouring domains, indicate that the above domain structure corresponds to "forbidden" ferroelastic domains of the phase <$EP2 sub 1 2 sub 1 2 sub 1>. On the basis of measurements for the temperature variation of the birefringence and observations of the domain structure transformations, one can conclude that the phases with the symmetries <$EP2 sub 1 3> and <$EP2 sub 1> coexist above <$ET sub c1>, in the compounds with x = 0,7 - 1,0. The phase transition temperatures <$ET sub c1 ,~T sub c2>, and <$ET sub c3> obtained from the temperature birefringence variations agree well with those obtained previously, using the studies of thermal expansion and ultrasonic wave velocities.

Analysis of Singularity Properties of the Radiation Field in Low-Mode Optical Fibres. - ISSN 1609-1833

We analyze the physical processes in optical fibres on the basis of the radiation field emitted from the output end. It is demonstrated that one can judge about the excitation coefficients of the guided modes in ideal optical fibres from the position of singularity point and equal intensity lines. We have obtained dependence of the excitation coefficients of guided optical vortices (OV) upon the displacement of the OV incident on the input fibre end. It is shown that the motion of the singularity point at the output end is caused by the rotational Doppler effect.

On the Temperature Behaviour of Optical Transmission Spectra of <$Egamma>-Modified Vitreous <$Eroman bold {As sub 2 S sub 3 }>. - ISSN 1609-1833

Temperature behaviour of the optical transmission of (-irradiated vitreous v-<$Eroman {As sub 2 S sub 3 }> is studied for the first time in the absorption edge region. It is shown that temperature dependences of the main transmission characteristics are different for (-irradiated and non-irradiated glasses. The difference is associated with the existence of specific coordination topological defects appearing in the <$Eroman {As sub 2 S sub 3 }> network due to (-irradiation.