• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.3
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• pp.401-406
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• 1998

For the applications in optical waveguides and devices, LiNbO_3$ single crystals need to overcome the weakness of optical damage due to the inhomogeneities of laser-induced refractive index. This problem can be solved by doping of Mg in LiNbO_3$ and proton exchange of LiNbO_3$. In this study, to understand the mechanism of optical damage resistance in LiNbO_3$, the changes of lattice defects in LiNbO_3$ caused by MgO doping and acid treatment were observed indirectly by $OH^-$ absorption bands using a FT-IR spectrophotometer. The effect of lattice defects on temperature, heat-treatment and polishing were also investigated. It is shown that MgO doping increases optical damage resistance by generating the defects of $Mg_{Nb}^{2+}$ in the lattice of LiNbO_3$, and that proton exchange by implantation of $H^+$ ion in the hexagonally closest packed oxygen layers on the surface of LiNbO_3$, makes lattice defects, which diffuse into the crystal after heat-treatment above $400^{\circ}C$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.1 no.1
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• pp.1-4
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• 1991

The applicability of $LiNbO_{3}$ as a substrate for fabrication of Ti-indiffused waveguide electro-optic devices is limited. Ti diffuses comparatively in congruently melting $LiNbO_{3}$; the Curie temperature of this material is too low to permit diffusion temperatures much above $1100^{\circ}C$ without the necessity of re-poling the crystal. Both of hese difficulties could be eliminated by incorporating certain dopants in $LiNbO_{3}$. Crystals of $LiNbO_{3}$ doped with Ti and Mg were grown and evaluated. The electroptic coefficients and birefringence of $LiNbO_{3}$ doped crystals were measured at ${\lambda}=.6328$ and $1.32\;$\mu{m}$. Curie temperatures were measured. The Curie temperature of both undoped and Ti-doped $LiNbO_{3}$ was $1130^{\circ}C$; that for Mg-doped $LiNbO_{3}$ was $30^{\circ}$ higher. From these data, a composition for the crystals was estimated. Thermogravimetric data confirmed this estimate and showed that the composition of Mg : $LiNbO_{3}$ was $49.3{\pm}0.2mole%\;Li_{2}O$ ; the composition of the undoped and Ti : $LiNbO_{3}$ samples was $48.6{\pm}0.2mole%$. Diffusion of Ti into both Mg-doped and Ti-doped $LiNbO_{3}$ crystals was studied as a function of $Li/NbO_{3}$ ratio and temperature.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.12 no.1
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• pp.27-30
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• 2002

ZnO co-doped Er:$LiNbO_3$ single crystal thin films have been grown on $LiNbO_3$ (001) substrate by liquid phase epitaxy (LPE) method. The melts of ZnO co-doped Er:$LiNbO_3$ was fixed $Er_2O_3$, concentration (1 mol%) and different ZnO concentrations 3 and 5 mol%. The crystallinity of ZnO co-doped Er :$LiNbO_3$ films became better than the $LiNbO_3$ substrate. At ZnO 5 mol% concentration, the surface of ZnO co-doped Er:$LiNbO_3$ film is affected by compressive stress along both the perpendicular and the parallel direction. Also the surface of ZnO 3 mol% co-doped Er:$LiNbO_3$film is smoother than the original $LiNbO_3$ substrate surface.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.3
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• pp.120-123
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• 2005

The 5 mol% ZnO doped $LiNbO_3$ film and the 2 mol% MgO doped $LiNbO_3$ film were grown on the $LiNbO_3$ (001) substrate by liquid phase epitaxy (LPE) method with $Li_2CO_3-V_2O_5$ flux system. The crytsallinity and the lattice mismatch between $Zn:LiNbO_3$, film and $Mg:LiNbO_3$, film were analyzed by x-ray rocking curve (XRC). In addition, the ZnO and MgO distribution in the cross-section of the multilayer thin films was observed using electron probe micro analyzer (EPMA).

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.5 no.2
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• pp.129-134
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• 1995

Bulk properties of single crystals $KMnCl_3$ undoped and Mg- doped $LiNbO_3$ were examined by using the neutron scattering technique. This study shows that the good -looking samples by polarized light have to be examined by the. neutron scattering to ensure the bulk properties of single crystal. Large mosaic spread in KMnCb indicated the crystal is not in a single domain. Many parts are relatively randomly directed against crystal axis with close angle each other. For the small mosaic spread of Li~ in the scattering pattern, it is found that some large domains have close orientations. Mg doped Li~ is turned out to be a well grown one.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.4
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• pp.532-542
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• 1996

The electrical and optical properties of the annealed $LiNbO_{3}$ single crystal with congruently melting composition and MgO or ZnO doped $LiNbO_{3}$ single crystal grown by the FZ method. The electrical and optical properties such as electrical conductivity, dielectric constant (Curie temperature), electro-mechanical coupling factor, optical transmittance and refractive indices of the grown crystals were measured and the nonlinear refractive indices of the grown crystals were calculated theoretically. The doping effects of MgO and ZnO were investigated by comparing the electrical and optical properties of the undoped $LiNbO_{3}$ single crystal and those of the $LiNbO_{3}$ single crystals doped with MgO or ZnO.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.1
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• pp.20-22
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• 1999

The effect of dopant and stoichiometry on the physical and optical properties of $LiNbO_{3}$ were studied. We prepared three samples, undoped, MgO doped $LiNbO_{3}$ with congruent composition and near-stoichiometric $LiNbO_{3}$. Dielectric constant and transmittance in UV/VIS/IR light range were measured. The results showed that the features for high [Li]/[Nb] were similar to those for low [Li]/[Nb] but with high [Mg].

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.1 no.2
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• pp.71-78
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• 1991

The congruent composition of $LiNbO_3$ was determined by measuring Curie temperature($T_c$) of crystals and residual melt grown from the range 48.45 to 48.60mole%$Li_2O$ melts. The $T_c$ of $LiNbO_3$ varied with compositon largely. The variation of $T_c$ with composition was found to follow $T_c=l0.4184c^2-962. 996C + 23342$, where C is mole % LizO. DSC-1500 was used to measure $T_c$. Distribution coefficients for $LiNbO_3$$ LiNbO_3$ contains 48.52mole$Li_2O$ and has a measured Tc of $1145{\pm}^{\circ}C$

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.1
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• pp.11-14
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• 2009

Yb and Zn co-doped $LiNbO_3$ single crystal rods which had a diameter of 2 mm and a length of $15{\sim}25 mm$ were grown by micro-pulling down (${\mu}-PD$) method. The single crystals were successfully grown and had a uniform diameter and a smooth surface without crack. We realized of $LiNbO_3$ single crystals were hexagonal structure to compare with peaks of $LiNbO_3$ powder by Raman spectra. The threshold level of Zn concentration which is effective for optical damage were observed as about 1 mol% with IR transmission spectra.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.5 no.1
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• pp.1-10
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• 1995

Congruent $LiNbO_3$ single crystals and $LiNbO_3$ : Mg single crystals, having high resistance to optical damage, doped with MgO to the levels of 2.0, 5.0 and 7.0 mol% were grown successfully by CZ method and optical damage of each crystal was measured by compen. sation method. With doping level reaching about 5 mol%, there was an abrupt change in the features of optical absorption edge and $OH^-$ absorption band. From these data, we confirmed indirectly the threshold in MgO doping level. When the MgO doping amount reaches about 5 mol% in the melt, $Mg^{2+}$ occupies Nb site and becomes $Mg_{Nb}^{2+}$, resulting in the sharp increase of optical damage resistance. The optical damage resistance of $LiNbO_3$ : Mg was improved more than three times when MgO amount in the melt reaches 5 mol%.