M. O. Zabezhailov

Russian Academy of Sciences, Moscow, Moscow, Russia

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Publications (9)5.54 Total impact

  • A. L. Tomashuk, M. O. Zabezhailov
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    ABSTRACT: Samples in the form of transverse slices of rods and optical fiber preforms made from the high-hydroxyl KU-1 and low-hydroxyl KS-4V silica by the plasma outside deposition (POD) method are γ-irradiated to a dose of ∼1 MGy (SiO2). Next, the radial dependences of the radiation-induced nonbridging oxygen hole center (NBOHC) and E′-center (three-coordinated silicon) in the samples are constructed by measuring the amplitudes of their 4.8 and 5.8 eV absorption bands, respectively. Based on the analysis of these radial dependences and considering the temperature and duration of the preirradiation heat treatment of the rods and preforms at the POD-installation, we determine the ratio of the oscillator strengths of the above bands and the microscopic thermoinduced processes occurring during preform fabrication and producing precursors of the radiation-induced NBOHC and E′-center. These processes are found to be associated with the escape of either H2 or H2O from neighboring hydroxyl groups, and, therefore, can occur in high-hydroxyl silica only. It is concluded that enhancement of the radiation resistance of high-hydroxyl silica optical fibers requires decreasing the temperature and duration of the preform fabrication process, in particular, changing from the POD-technology to the low-temperature plasmachemical vapor deposition (PCVD) or surface PCVD (SPCVD)-technology.
    Journal of Applied Physics 04/2011; 109(8):083103-083103-11. · 2.21 Impact Factor
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    ABSTRACT: The effect of the preform fabrication procedure on the radiation-induced absorption in KU-1 and KS-4V high-purity silica glasses was investigated (these glasses are used in fiber preform fabrication via outside fluorosilicate glass deposition on substrate rods and in the rod-in-tube process). The results demonstrate that the deposition of a reflective cladding onto KU-1 rods drastically increases the radiation-induced UV absorption of the rods. In particular, the concentrations of radiation-induced nonbridging oxygen hole centers and E centers in gamma-irradiated KU-1 rods with a fluorosilicate cladding are an order of magnitude higher than those in rods that were not heat-treated in plasma torch flames. At the same time, the deposition of a reflective cladding on KS-4V rods has little effect on the concentrations of these radiation-induced color centers. The radiation-induced absorption in KU-1 rods depends on the deposition temperature and duration but is insensitive to the composition of the gas mixture in the torch (in particular, to the presence of fluorination agents) and the presence of a fluorosilicate cladding. It is shown that, in preforms fabricated by the rod-in-tube process, the net concentration of radiation-induced color centers in the substrate rod is lower compared to the outside plasma deposition of fluorosilicate glass on the rod.
    Inorganic Materials 03/2005; 41(3):315-321. · 0.38 Impact Factor
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    ABSTRACT: The IR optical absorption spectra and the Raman spectra of rods made of high-purity quartz glass of the KU-1 and KS-4V grades have been studied in comparison to those measured for the blanks of optical fibers fabricated from this glass using the plasma outside deposition (POD) technology. Based on these data, a discussion is presented of the most probable mechanisms responsible for an increase in the γ-radiation-induced absorption in high-purity quartz glasses as a result of their processing in the course of optical fiber fabrication using the POD technology.
    Technical Physics Letters 01/2005; 31:498-499. · 0.56 Impact Factor
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    ABSTRACT: The optical loss spectra of as-prepared and gamma-irradiated microstructured multimode fibers with KU-1 silica cores are analyzed. Experimental evidence is presented that leakage losses in such fibers can be prevented by producing, in their cladding, two layers of channels separated by thin glass walls. The strong absorption at 630 nm in the radiation-induced loss spectra of the fibers is shown to arise from nonbridging oxygen. The mechanisms underlying the formation of precursors to this color center are discussed, and the possible approaches to suppressing the 630-nm absorption are outlined.
    Inorganic Materials 10/2004; 40(11):1229-1232. · 0.38 Impact Factor
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    ABSTRACT: This paper addresses the particular need to develop suitable fabrication techniques of glasses to improve the radiation-resistance and extend the lifetime of optical fibres in high radiation background. Two radiation hardening techniques based on hydrogen and fluorine doping of glass have been applied on step index pure silica core optical fibres. The radiation-induced optical absorption and luminescence have been measured in gamma and fission reactor irradiation conditions at SCKCEN, Mol Belgium. The experimental results show that the lowest optical absorption is achieved in the hydrogen-treated fibre sample. However, the luminescence effect remains significant in any type of fibre and cannot be reduced by the investigated radiation hardening techniques.
    Journal of Nuclear Materials 01/2004; · 2.02 Impact Factor
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    ABSTRACT: The light emission intensity at the wavelength of 400-750 nm in the KU-1 silica core (OH content 1000 ppm) fiber waveguide under irradiation at BARS-6 pulsed fission reactor (pulse duration 80 microsecond(s) , dose per pulse <5.5x10^12 n/cm^2 (9 Gy), dose rate <7x10^16 n/cm^2s (1.1x10^5 Gy/s) have been measured. The intensity of radiation-induced light emission has been found to depend on intensity of probing light. Lower intensity of the light emission has been observed for higher intensity of probing light (lasers, wavelength 532 and 632 nm). The light emission quenching occurs at the wavelengths shorter and longer than the wavelength of the probing light, and also at the equal wavelengths.
    Proc SPIE 01/2002; 4547:74-77.
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    ABSTRACT: Aluminum-coated optical fibers are loaded with molecular hydrogen by keeping the fibers in an H2 atmosphere at high pressure and temperature. A high H2 concentration in the fiber glass (up to 1 at. %) has been obtained by this technique. A drastic reduction of radiation-induced absorption in the visible spectral region in H2- containing Al-coated fibers is demonstrated. The formation mechanism is the H(I)-center is analyzed.
    Proc SPIE 01/2002;
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    M.O. Zabezhailov, A.L. Tomashuk, I.V. Nikolin, K.M. Golant
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    ABSTRACT: Loss spectra are compared in H<sub>2</sub>- and D<sub>2</sub>-loaded and gas-free N-doped fiber samples after γ-irradiation. It is found that D<sub>2</sub>-loading allows reduction of induced absorption at the wavelengths of 1.30 and 1.55 μm by a factor of ∼5 at a total dose of ∼1 MGy. H<sub>2</sub>-loading is shown to be less efficient, owing to H<sub>2</sub> and OH-group absorption bands increasing the total loss in the telecom spectral windows. Pretreatment of fibers via D<sub>2</sub>-loading and pre-irradiation appears to be a promising radiation-hardening technique.
    Radiation and Its Effects on Components and Systems, 2001. 6th European Conference on; 10/2001
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    M.O. Zabezhailov, A.L. Tomashuk, I.V. Nikolin, K.M. Golant
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    ABSTRACT: Radiation-induced absorption spectra and radial distribution of non-bridging oxygen over the fiber core are compared in fibers and preform slices fabricated under different technological regimes with KU-1 and KS-4V silicas in the core. The radiation-induced non-bridging oxygen concentration is found to peak at the core-cladding interface. Fiber perform fabrication and fiber drawing processes are found to have different influence on its value in fibers with low-OH (KS-4V) and high-OH (KU-1) silicas in the core. The precursors of non-bridging oxygen near the core-cladding interface are argued to arise at the stage of preform fabrication at least in the case of KU-1 fibers. Their concentration decreases with increasing the fluorine concentration in the cladding. In the case of KS-4V fibers the increase of the radiation-induced non-bridging oxygen concentration at the core periphery is argued to have a different nature as compared to KU-1 fibers.
    Radiation and Its Effects on Components and Systems, 2001. 6th European Conference on; 10/2001