Browsing by Author "Shah, Rajiv R."

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    Characterization of Iron Doped Lithium Niobate for Holographic Storage Applications
    (1976-06-20) Shah, Rajiv R.; Kim, Dae M.; Rabson, Thomas A.; Tittel, Frank K.
    A detailed study of eight systematically chosen Fe:LiNb03 crystals is presented. Correlation between the photorefractive sensitivity and various chemical properties of Fe:LiNb03 is investigated in order to ascertain optimum performance of Fe:LiNb03 crystals in holographic storage and display applications. Concentrations of Fe2+ and Fe3+ ions have been determined from optical and EPR spectra while impurities have been detected from x-ray emission and infrared spectra. Particular emphasis is placed on investigating the dependence on Fe3+ ion concentrations of the photorefractive sensitivity. The photorefractive sensitivity is shown to depend primarily on the concentration of Fe2+ ions in Fe:LiNb03. This fact seems to suggest that Fe2+ ions are the impurity centers responsible for the photorefractive effect in Fe:LiNb03. Spectral dependence of the photorefractive sensitivity and its modification due to oxygen annealing are also reported. Our results indicate that an unannealed Fe:LiNb03 crystal containing 0.05 mole % Fe with 20-25% of the ions in the Fe2+ state and the remainder in the Fe3+ state possesses the most favorable photorefractive sensitivity.
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    Interferometric Studies of Mode Locked Nd3+: Glass Lasers
    (1975-03-20) Shah, Rajiv R.; Rabson, Thomas A.; Kim, Dae M.
    A general technique for measuring the electric field vector of the ultrashort pulses from mode locked laser systems is described. The technique is applied to perhaps the most difficult laser to analyze, the dye mode locked, Nd3+:glass laser whose pulses change rapidly in bandwidth and amplitude, are chirped, and can occur in quite short pulse trains. The results of these measurements indicate a rather rapid change in the phases between modes and a plot of the phase change as a function of mode frequency has been obtained.
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    Nonlinear Dynamic Theory for Photorefractive Phase Hologram Formation
    (1976-01-20) Kim, Dae M.; Shah, Rajiv R.; Rabson, Thomas A.; Tittel, Frank K.
    A nonlinar dynamic theory is developed for the formation of photorefractive volume phase holograms. A feedback mechanism existing between the photo-generated field and free electron density, treated explicitly yields the growth and saturation of the space charge field in a time scale characterized by the coupling strength between them. The expression for the field reduces in the short time limit to previous theories and approaches in the long time limit the internal or photovoltaic field. Additionally, the phase of the space charge field is shown to be time dependent.
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    Study of the Equivalent Electron Drift Field Characteristics in LiNb03 by Phase Holography
    (1976-06-20) Kim, Dae M.; Shah, Rajiv R.; Rabson, Thomas A.; Tittel, Frank K.
    An analysis of the diffraction efficiency of photorefractive holograms in ferroelectric crystals is shown to provide a novel technique for determining the nature and magnitude of the equivalent electron drift field. For a Fe doped lithium niobate crystal (0.05% per mole) we find that the total field consists of an intensity independent internal field of 8.5 KV/cm and a photo-generated field given by the conversion factor 1.4Ã 106 V-cm/W.