Thermal Fixing of Holographic Gratings in Nearly Stoichiometric LiNbO3 Crystals
MAGYAR TUDOMANYOS AKADEMIA BUDAPEST
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The thermal decay of holographic gratings recorded using the conventional two-wave mixing technique has been studied in congruent and nearly stoichiometric LiNbO3 crystals doped with Mn. The activation energies of this process have been determined in the 70-130 deg C range for congruent and 20-80 deg C range for nearly stoichiometric crystals, the obtained values being 1.06 - 0.03 and 1.10 - 0.03 eV, respectively. The kinetics of the OH- absorption spectrum has also been studied in undoped nearly stoichiometric LiNbO3 between 40-120 deg C. The time dependence of the band intensities can be characterized by exponential time constants obeying the Arrhenius-law. The average activation energy, Esub a approx. 1.1 - 0.1 eV is in good agreement with those obtained from the thermal decay indicating that the hologram fixing process in nearly stoichiometric LiNbO3 is governed by proton migration.
- Physical Chemistry