Band structure treatment of the influence of nonstoichiometric defects on optical properties in LiNbO3

We present a band structure approach in connection with a molecular dynamic s cluster optimization that accounts for various structural modifications r elated to the nonstoichiometry of LiNbO3 crystals. Variation of optical pro perties with the deviation from the stoichiometric composition can be under stood within this approach. The particular role of the electron-phonon cont ributions to the electro-optic coefficient is shown. Model calculations yie ld a large dependence of the electro-optic coefficient r(22) on the crystal composition, in agreement with the experimental data. The observed minimum of the r(22) coefficient versus nonstochiometry is explained within a micr oscopic approach. The r(33) tensor component shows substantially different behavior versus the stoichiometry. (C) 2001 American Institute of Physics.