Calculating and matching the spatial frequency spectrum for recording quasi-fourier holograms on photothermoplastic media

We propose a modification of the optics for recording Fourier holograms. We calculate the spatial frequency spectra of the interference field. We have studied the effect of the parameters of the objectives on the spectral matching, determined by the recording optics and the resonance type of transfer characteristic for the photothermoplastic recording medium. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 1, pp. 124–128, January–February, 2006.     

Holographic recording media based on oligomers and co-oligomers with organic dye additives

We have created holographic recording media based on films of carbazolyl-, fluorenyl-, naphthyl-, and anthracenyl-containing oligomers and co-oligomers in which an intraionic organic dye is used as the sensitizer. We have established that the photoconductivity of the films and the photosensitivity of the recording media are higher in the case of co-oligomers with different donor moieties. We conclude that in the films of co-oligomers with different donor moieties in the “end” groups of the polymer chain, there is reduced probability of formation of excimers, which are centers for capturing photogenerated charge carriers, and therefore the photoconductivity of the film increases. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 1, pp. 132–135, January–February, 2007.     

Multiple recording of rainbow holograms on the same section of a photosensitive material

Abstrac A technology is proposed for multiple recording of holograms on the same section of thin recording media using the technique for obtaining rainbow holograms. It is shown that in this case the individual holograms can be reconstructed and read independently of one another. Experimental results are presented. Zh. Tekh. Fiz. 68, 127–129 (February 1998)     

Electric conductivity of siliconorganic polyhomoconjugated polymer films upon adsorption of volatile organic compounds

The electrophysical parameters of polyhomoconjugated organosilicon polymer films are studied, and variation of their conductivity under the action of water, toluene, and ammonia vapors is measured. Films 1–2 μm thick are prepared by the casting method from a solution of poly[2,2-dimethyl-2-sila-1,3-propylene-(4, 4′-biphenylene)]a (polymer I) and poly[2-n -butyl-2-phenyl-2-sila-1,3-propylene-(4, 4′-biphenylene)]a (polymer II). In the course of conductivity measurement, organic volatiles and water are adsorbed due to a stepwise rise in the pressure over the sample from 10⁻³ to 10⁻¹ Torr. The initial values of the resistivity of polymers I and II are estimated as 4 × 10⁹ Θ cm. Exposure of the films to organic volatile vapors and water vapor causes a reversible change in the conductivity of the films. For polymer-I films, the conductivity upon adsorption of ammonia, toluene, and water vapors exceeds the initial value by 150, 10, and 600 times, respectively. The sensitivity of polymer-II films is lower by a factor of 1.5–2.0. The time of conductivity variation as the vapors are injected and evacuated is within 10 and 30 s, respectively. The mechanisms of organic volatile and water adsorption on the surface of polyhomoconjugated organosilicon polymer films are compared with adsorption mechanisms on the surface of π-polyconjugated organic films.     

Morphology and spectral properties of thin films of benzoxazole derivatives of biphenyl

We have studied the spectral properties and morphology of thin films (TVD films) formed by thermal vacuum deposition of 4,4′-bis[(E)-1-(1,3-benzoxazol-2-yl)-2-ethenyl]-1,1′-biphenyl and its substituted derivatives. We have shown that introducing bulky 2,2′-oxyhexyl substituents into the biphenyl units leads to a shift of the fluorescence maximum for the TVD films toward shorter wavelengths, a decrease in their photostability, and aggregation of the films during storage. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 3, pp. 300–303, May–June, 2007.     

Effect of substituents in benzoxazole derivatives of biphenyl on the optical properties and photostability of their thin films

We have studied the characteristic features of the luminescence of thin films, formed by deposition from solutions and thermal vacuum deposition (TVD), of 4,4′-bis[(E)-1-(1,3-benzoxazol-2-yl)-2-ethenyl]-2-fluorobiphenyl (BPh-1) and 4,4′-bis[(E)-1-(1,3-benzoxazol-2-yl)-2-ethenyl]-2,2′-difluorobiphenyl (BPh-2). We have established that fluorine atoms in the biphenyl moiety of the benzoxasole derivatives significantly improve the stability of the TVD films relative to oxidative aging compared with hexyloxy substituents. Irradiation with UV light stimulates quenching of luminescence and structuring of the TVD film of the difluoro-substituted derivative.     

Photopolymeric Material Based on an Organic-Inorganic Sol-Gel Matrix for Holography

The methods of formation and properties of a holographic photopolymeric material (PPM) of thickness 0.5–1.0 mm in a hybrid organic-inorganic matrix are investigated. The matrix is formed by synthesizing the cofspolymer N-vinylpyrrolidone with triethoxyvinylsilane with subsequent hydrolytic condensation of this copolymer with tetraethoxysilane pre-sol. It is shown that a solid hybrid matrix, stable against cracking, can be formed at a pre-sol-copolymer weight ratio of 1:4. Transmission and reflection holograms in a hybrid PPM of thickness 0.46 mm are recorded, and it is shown that the angular selectivity of the transmission hologram is 0.17° and that the material shrinkage measured from changes in the Bragg angle of the transmission hologram does not exceed 0.7%. The holographic characteristics obtained have been improved by an order of magnitude as against PPM in an organic polymeric matrix. Formation of a photopolymeric material for recording highly selective holograms in a hybrid organic-inorganic matrix is a promising approach in the development of photosensitive media for a three-dimensional holographic memory. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 4, pp. 551–556, July–August, 2005.     

Electro- and Magneto-Optical Properties of Films of Polycomplexes of 4-Methacryloyloxy-(4′-Carboxy-3′-Oxy)Azobenzene with Metals

The electrical conductivity, photoconductivity, and electrical and magneto-optical properties of the films of new polycomplexes of 4-methacryloyloxy-(4′-carboxy-3′-oxy)-azobenzene with nickel and cobalt have been investigated. The electrical conductivity and photoconductivity in the visible region of light are determined by the orientation effects of azobenzene groups as well as by generation and transfer of charge carriers between them. A change in the spatial orientation of photoinduced dipole moments of azobenzene groups in an external electric or magnetic field is attributed to the appearance of forces acting on electrically charged magnetic ions of a metal and that are rigidly connected with these groups. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 4, pp 499–503, July–August, 2005.     

Influence of atomic ordering on the magnetic properties of FePd,FePt, and Fe<Subscript>50</Subscript>Pd<Subscript>50−<Emphasis Type="Italic">x</Emphasis></Subscript>Pt<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> alloy films

The phase composition, crystal structure, and magnetic properties of films of the ordered alloys FePd, FePt, and Fe₅₀Pd_{50 − x} Pt _x , where x = 1–10 at %, were analyzed. The spectral dependences of the magnetic rotation and optical absorption were taken. The effect of heat treatment on the crystal structure, magnetization, and coercive field strength of the ordered alloy films was studied. The influence of the degree of atomic ordering on the perpendicular magnetic anisotropy was investigated. It was shown that films of ordered FePd and FePt alloys of equiatomic composition and films of Fe₅₀Pd_{50 − x} Pt _x , where x = 1–10 at %, can serve as media for magnetic and thermomagnetic data recording and storage.     

Effect of solvation on polarization characteristics of fluorescence for 1,3,4-oxadiazole derivatives in binary solvents

We have studied the degree of fluorescence polarization for 1,3,4-oxadiazole derivatives in the binary solvents hexane-ethanol, toluene-ethanol, toluene-acetonitrile, 2-propanol-water, dioxane-water, 2-propanol-glycerol, glycerol-water vs. the composition of the solvent. We have shown that in systems with predominant universal interactions, the characteristic changes in the degree of polarization reflect the change in the viscosity of the mixture, while in systems with pronounced specific interactions they reflect the characteristic structural features of the fluorescent centers. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 5, pp. 677–683, September–October, 2008.     

New azo-dye-doped polymer systems as dynamic holographic recording media

Polymer materials show their impact on optical storage technology for developing high information density and fast access-type memories with a high read-out efficiency. New azo-dye-doped polymer materials have been developed and used for recording dynamic holograms. Dynamic holograms with reasonably high diffraction efficiency have been recorded at 468 nm, and the efficiency of the Write, Read and Erase (WRE) cycle in these azo-dye-doped polymer materials was determined. Significant observations in these materials are: (i) there is no need to change the polarization of the writing beam to erase the recorded holograms, (ii) the whole WRE cycle is very fast (3–6 s) and (iii) recording of more than 250 WRE cycles without any fatigue of the recording materials is possible.     

Structure of polyethylene films containing copper nanoparticles

We have used IR spectroscopy to study the effect of Cu nanoparticles on the degree of crystallinity in nanostructured high-pressure polyethylene (PE) films. We have shown that for ∼1 mass % Cu in the polyethylene films, we observe the maximum degree of crystallinity. This is connected with commensurability between the nanoparticle sizes and the periodicity of the three-dimensional structure of the straightened polyethylene chains in its transitional phase. Dielectric measurements on the nanostructured polyethylene films are support for the features observed in the IR spectra for the systems under study. From the data obtained, we hypothesize that we can control degree of crystallinity of the polymer by varying the sizes of the nanoparticles and the type of polymer. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 3, pp. 408–410, May–June, 2006.     

Recording volume holograms on color centers in a CaF2 crystal

The conditions for preparing photochromic CaF₂ crystals, recording holograms with 532-nm radiation in them, and postexposure photothermal treatment of samples with holograms that provide the formation of holographic elements of significant thickness (about 1 cm) are considered. It is shown that the diffraction efficiency of volume holograms in such crystals in the case of reading out by radiation with wave-lengths of 532 and 632.8 nm can be as high as 10–15%. The role of the recording mechanism and the Borrmann effect in the fabrication of these holograms is demonstrated.     

Production of SiO2 films from alkoxides and their optical properties

The specific features of spectrochemical properties of active silica-gel films in air media with various pH have been studied. SiO₂ films were obtained by acid hydrolysis of tetraethoxysilane. The optical properties were controlled by immobilization of indicators (bromocresol purple, phenol red). The possibility of using them as optical-fiber sensors is shown. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 4, pp. 503–506, July–August, 2000.     

Solvent effects on the electrical and optical properties of composite carbon nanotube/MEH-PPV films

Optical signals were used to modulate the resistance of single-walled carbon nanotube–polymer composite films for development of optical switching devices. Films were fabricated from nanotubes dispersed in poly(2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) solutions in either tetrahydrofuran (THF) or toluene. MEH-PPV was affected by the solvent choice, with THF causing an absorbance shift to shorter wavelengths. Composite films formed from THF dispersions showed 1–4% resistance decreases when illuminated with a green diode laser. Illumination of toluene-based films showed up to 5.4% resistance decreases, smaller than expected based on the polymer solution absorbance. Fluorescent emission from the polymer in toluene appears to inhibit charge transfer from the polymer to the nanotubes. THF films were unaffected by illumination with a red diode laser, while toluene dispersion films showed resistance decreases up to 1%. Nanotube dispersion and film formation reproducibility, evaluated for both the solvents, showed that the solvent affected film resistance and dispersion stability.     

Self-deflection of laser beams during holographic recording in photorefractive crystals

We have observed dynamic deflection of laser beams reflected from a crystal surface during recording of dynamic holograms in a photorefractive crystal. A theory describing the principal experimental facts is presented. The model takes into account the nonlinear interaction of space-charge waves. Pis’ma Zh. éksp. Teor. Fiz. 70, No. 4, 253–256 (25 August 1999)     

Impact of ethylene carbonate on electrical properties of PVA/(NH4)2SO4/H2SO4 proton-conductive membrane

A new proton-conductive membrane (PCM) based on poly (vinyl alcohol) and ammonium sulfate (NH₄)₂SO₄ complexed with sulfuric acid and plasticized with ethylene carbonate (EC) at different weight percent were prepared by casting technique. The structural properties of these electrolyte films were examined by XRD studies. The XRD patterns of all the prepared polymer electrolytes reveal the amorphous nature of the films. ac conductivity and dielectric spectra of the electrolyte were studied with changing EC content from weight 0.00 to 0.75 g. A maximum conductivity of 7.3 × 10⁻⁵ S cm⁻¹ has been achieved at ambient temperature for PCM containing 0.25 g of ethylene carbonate. The electrical conductivity σ, dielectric constant ε′ and dielectric loss ε″ of PCM in frequency range (100 Hz to 100 KHz), and temperature range (300–400 K) were carried out. Measurement of transference number was carried out to investigate the nature of charge transport in these polymer electrolyte films using Wagner’s polarization technique. Transport number data showed that the charge transport in these polymer electrolyte systems was predominantly due to ions. The electrolyte with the highest electrical conductivity was used in the fabrication of a solid-state electrochemical cell with the configuration (Mg/PCM/PbO₂). Various cell parameters ldensity, and current density were determined. The fabricated cells gave capacity of 650 μAh and have an internal resistance of 11.6 kΩ.     

Perpendicular magnetic anisotropy in Co50Pt50 and Co50Pt50 ? x Pd x films

Atomic ordering and its effect on the perpendicular magnetic anisotropy and coercive force in Co₅₀Pt₅₀ and Co₅₀Pt_{50 − x} Pd _x (x = 3–10 at %) alloy films are investigated. The dependence of the coercive force on the film thickness is studied. It is shown that thin films of the ordered alloys become magnetically uniaxial with the easy magnetic axis normal to the plane of the film. Such films can be used for magnetic and thermomagnetic data recording and storage.     

AC conductivity and relaxation behavior in ion conducting polymer nanocomposite

We report the ac conductivity and relaxation behavior analysis for a heterogeneous polymer–clay nanocomposite (PNC) having composition (polyacrylonitrile)₈LiCF₃SO₃ + x wt.% dodecylamine modified montmorillonite. Charge transport behavior in an ionically conducting PNC has been analyzed systematically and correlated with the macroscopic parameters like polymer glass transition temperature and available free mobile charge carriers. Intercalation of cation coordinated polymer into the nanometric clay channels has been confirmed by high-resolution transmission electron microscopy. The electrical properties of the intercalated PNC films have been studied using complex impedance/admittance spectroscopy. Excellent correlation of relaxation behavior with polymer glass transition temperature (T _g) confirmed the objectives of the work. An analysis of dielectric relaxation indicates that PNC films are lossy when compared with polymer–salt film. This result is a direct outcome of faster ion dynamics leading to strong electrode polarization effect due to the accumulation of charge carriers at the interface.     

Effect of annealing on structure and magnetic properties of Fe-N and Fe-Ti-N thin films

The structure and magnetic properties of Fe-N and Fe-Ti-N films have been studied as a function of annealing temperature T_a with a transmission electron microscope and a vibrating sample magnetometer. The as-prepared Fe-N films consist of the γ^′-Fe₄N and α^′′-Fe₁₆N₂ phases, and the Fe-Ti-N films are composed of the γ^′-Fe₄N, α^′′-Fe₁₆N₂, and TiN phases. The structural changes with annealing temperature in the Fe-N films are distinct. The α^′′-Fe₁₆N₂ decomposes into α+γ^′ phases in the Fe-N film annealed at about 300 °C, and it disappears in the film annealed at 350 °C. Annealing of the Fe-Ti-N films shows no structural changes between room temperature (RT) and 500 °C. The saturation magnetization 4πM_S and coercivity H_c of the Fe-N films change drastically with the annealing temperature T_a, whereas those of the Fe-Ti-N films do not change with T_a up to 500 °C. These results indicate that the additon of Ti may improve the thermal stability of Fe-N films. Recieved: 6 Juli 1998 / Accepted: 19 Oktober 1998 / Published online: 10 March 1999