• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.1
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• pp.6-17
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• 1997

Lithium niobate single crystals with various [Li]/[Nb] ratios were grown by the Czochralski method from melts having compositions varing between 48.6 ~ 58.0 mol % $Li_2O$. A vapor transport equilibration technique has been used to improve the homogeneity and adjust the [Li]/[Nb] ratio in small $LiNbO_3$ single crystals grown by the Czochralski method. When equilibrated with a Li-rich powder (65 mol%$Li_2O$), containing a mixture of $LiNbO_3$ and $Li_3NbO_4$, crystals of nearly stoichiometric composition can be obtained. This was established by studying the composition dependence of the following properties; lineshape, intensity and linewidth for the electron paramagnetic resonance (EPR) of $Fe^{3+}$ energy of the fundamental absorption edge and $OH^-$ absorption spectra.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.3
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• pp.301-308
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• 1996

Domain structure and properties of LiNbO3 single crystals grown by continuous method (Orr's method) were characterized. It was found that the growth striation of the grown crystals correspond with domain structure and the positive-negative domains were repeated with the perpendicular direction to the C axes. The formation of negative domains were related to the rapid crystal growth rate. The measured dielectric constant of the grown crystal was 140∼150 at 100 kHz at the room temperature and Curie point was 1153℃.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.5 no.4
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• pp.378-385
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• 1995

The growth processes of improved methods for MBE, LPE and $\mu$ - PD methods are discussed taking the oxide materials, especially those of Bi - Sr - Ca - Cu family $LiNbO_3$ and $K_3Li_2Nb_5O_{15}$ family as examples. It is suggested that the crystal growth far from equilibr iu m including composition homogeneity has been achieved to satisfy in understanding and controlling the atomic interfaces.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.12
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• pp.1051-1057
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• 2000

A traveling-wave CPW(coplanar waveguide) electrode with abruptly broken input/output-taper for LiNbO$_3$optical modulator was designed and fabricated. The electrical characteristics of traveling-wave electrode on z-cut LiNbO$_3$crystal with SiO$_2$buffer layers were measured by network analyzer. To confirm the possibility of the electro-optic modulator electrode, detailed calculations of the impedance, microwave effective index and attenuation constants are presented as a function of the microwave electrode thickness, but the buffer layer thickness is fixed as 1${\mu}{\textrm}{m}$. These characteristics are discussed from the viewpoint of the device optimization and are expected to be design guides for the LiNbO$_3$modulator’s electrodes.

• Journal of the Korean Institute of Telematics and Electronics
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• v.25 no.3
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• pp.343-351
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• 1988

Planar optical waveguides are fabricated on a Y-cut LiNbO3 single crystal substrate by Ti indiffusion method. From data measured by the bright M-line spectroscopy, refractive index profiles are reconstructed by WKB approximation method. Then, single strip, X-crossing strip, and Y-brinch strip optical waveguides are fabricated on X-cut LiNbO3 single crystal substrate, with waveguide patterns made by the laser beam direct writing method. And their near-field intensity profiles are observed after coupling the light to the waveguide edges.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.3B
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• pp.267-274
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• 2002

In this paper, the real-time color pattern recognition system is experimented by optical approach using the SLM(TH LCD) and a photorefractive material. In the implemented system, the character patterns to recognize are controlled of an SLM, and a 10mm thick LiNbO$_3$ crystal having high angular selectivity and photorefractive effect is used for recording materials. The shape and color informations of the red or green color patterns are excellently discriminated at independent positions by real-time processing, as the results obtained by proposed optical architecture.

• Journal of the Korean Ceramic Society
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• v.29 no.3
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• pp.189-194
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• 1992

In order to grow a 127.86$^{\circ}$rotated LiNbO3 single crystal with good characteristics of surface acoustic wave (SAW) up to 80 mm in diameter, the temperature gradient of furnace, the growth rate and the rotation rate of crystal were changed. We could grow a crystal which had few macro defects at the conditions of temperature gradient as 30~6$0^{\circ}C$/cm, growth rate as 5 mm/hr and rotation rate as 8 rpm. The experimental ranges of the growth conditions are as follows. Temperature gradient was varied from 20 to 20$0^{\circ}C$/cm, growth rate as 5~7 mm/hr and crystal rotation rate as 6~12rpm.

• Journal of the Optical Society of Korea
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• v.7 no.3
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• pp.197-201
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• 2003

We investigated recording dynamics of a holographic grating in the photorefractive LiNbO$_3$ crystal under the low-intensity condition of recording beams. New expressions for the space-charge field and the recording time constant were obtained by solving the Kukhtarev equations under the global space -charge field, which is induced in the previous process of recording and erasing. Their validity can be confirmed by considering the limit that the period of the grating goes to infinity both theoretically and experimentally. It was found that the new expression for the recording time constant allows us to determine acceptor concentration to be $1.2${\times}$10^{21}m^{-3}$ for pure LiNbO$_3$ crystal and 2.5${\times}$$10^{21}m^{-3}$ for the 0.1 mol% iron doped LiNbO$_3$ crystal from the measured ratio of the recording time constant under the extremely large grating condition, in which the diffusion effect can be neglected, to that under the small grating condition.

• Korean Journal of Crystallography
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• v.4 no.2
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• pp.74-85
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• 1993

Single crystals of LiNbO3 have found extensive application in electro-optic and nonlinear optic devices. However, laser-induced refartive index inhomogeneities, which have been labeled opical damage impose limits on device optical damage in LiNbO3 is imporved if more than 4.5 rml% MgO is added to the melt The laser damage thrueshold increased as much as 100 times better then that of undoped crystals. The MgO doped cystal has thus been urterlsiv81y studied since then. In the study, Mgo:LiNbOs(MLA) single crystals dopsd with 0, 2.5, 5.0, 7.5, 10.0 mol% MgO have been grown by the czocrualski technique. The metls were prepared in the platinum crluible and 15∼20mm diameter crystals were grown with a length of 20∼30mm in a resitance heater. The growth rate was 2.5mm/hr, the rotation speed 15rpn. Before sawing MLN single crystals were annealed for 24 hours under atmosphere at a temperature of 1080℃. After sawing, we have found an annual ring cross section of MNA crystals only in the direction of perpendicilar to the c-axis. Nonuniform dispusion of MgO was pointed out that the cuties of the state of oxide were strongly affected by oxygen partial pressure in.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1997.06a
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• pp.109-113
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• 1997