Raman Scattering of Hydrogen-Ion-Exchanged LiNbO₃ Crystal

Raman spectra of LiNbO₃ crystals with different hydrogen-ion-exchanged time were examined. E(TO) and A₁ (TO) modes appear gradually in the transverse A₁- and E-symmetry spectra respectively with increasing the exchange time and the dependence of their intensities on the exchange time is also observed. We attribute these results to both the internal strains resulting from the ordering-disordering distribution of H ions in the sample and the enhanced photorefractive effect.