High Resolution XRD Studies on Mg, Cr and Nd Doped LiNbO3 Crystals
Undoped and doped LiNbO3 single crystals were grown by Czochralski technique. Comparative studies on these undoped, Cr doped, Mg doped, Mg:Cr codoped and Mg:Nd codoped LiNbO3 single crystals were carried out. Phase identification was done using powder XRD technique. The effect of doping and co-doping on crystalline perfection of these crystals was monitored using high resolution x-ray diffraction (HRXRD) technique. The diffraction curves (DCs) were recorded in symmetrical Bragg geometry for (006) diffracting planes using MoK￻ 1 radiation. tant is co-doping with Mg or Zn at a level above 4.5 mol%, which inhibits photorefractive properties of the material. Another potential application of LiNbO3 is in Nd 3+ based compact diode-pumped self-frequency doubled lasers that emit green radiation, useful for applications in optical data storage, and excitation sources to replace ion gas lasers and pumping of parametric oscillators and amplifiers (10). The
Influence of Non-Stoichiometric Defects on Optical Properties in LiNbO3
We present a band structure approach with a molecular dynamics cluster optimization which accounts for the various structural modifications related to the non-stoichiometry of LiNbO 3 crystals. The variation of the optical properties with the deviation from the stoichiometric composition can be understood within this approach. Particular role of the electron-phonon contributions to the electrooptics coefficient is shown. Model calculations yield a large dependence of the electrooptis coefficient r 22 on the crystal composition, in agreement with the experimental data. The observed minimum of the r 22 coefficient versus the non-stoichiometry is interpreted as originated from the non-centrosymmetry in the electrostatic potential distribution around Nb-O 6 clusters.
Structural distortion in TiSe2 and related materials-a possible Jahn-Teller effect?
A band Jahn-Teller type mechanism is proposed for the 2*2 superlattice distortion observed in TiSe2 below approximately 200K.