• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1850-1852
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• 2000

In this paper, new Partial Discharge (PD) detection technique using Pockels cell was proposed and considerable apparent chaotic characteristics were discussed. For this purpose, PD was generated from needle-plane electrode in air and detected by optical measuring system using Pockels cell, based on Mach-Zehnder interferometer, consisting of He-Ne laser, single mode optical fiber, 50/50 beam splitter and photo detector. A qualitative analysis was carried out by drawing Return map for the normalized time series of the detected PD signals. The results are as follows:(a) Fixed points, between 0.7 and 1.0, are appeared clearly in the right upper area of the return map as the increase in the number of obtained data.(b) Considerable periodicity have been remarked even though exact period and length can not be determined.(c) The self-similarity can be also observed inasmuch as the late paths do not follow the previous ones. Accordingly, exact quantitative analysis such as embedding dimension, fractal dimension, and Lyapunov exponents should be carried out for deducing the quantitative properties regarding PD phenomena.

• ETRI Journal
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• v.34 no.3
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• pp.361-368
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• 2012

A complete high-frequency small-signal circuit model of a 40 Gb/s butterfly electroabsorption modulator integrated laser module is presented for the first time to analyze and optimize its electro-optic (E/O) response and reflection characteristics. An agreement between measured and simulated results demonstrates the accuracy and validity of the procedures. By optimizing the bonding wire length and the impedance of the coplanar waveguide transmission lines, the E/O response increases approximately 5% to 15% from 20 GHz to 33 GHz, while the signal injection efficiency increases from approximately 15% to 25% over 18 GHz to 35 GHz.

• Korean Journal of Optics and Photonics
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• v.8 no.3
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• pp.245-249
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• 1997

An electro-optic polymer digital optical switch with a coupling region modified for optimum coupling is designed and demonstrated. Its branch waveguide is fabricated by reactive ion etching. Then, the modified coupling region is adiabatically introduced along the propagation direction from the branching point of the two waveguides, and it is implemented by photobleaching after the device fabrication. The structure of the modified coupling region and its refractive index profiles are designed to optimize and mode coupling in the Y-branch waveguide. Therefore, the switching performance of the device was shown to be enhanced with a fixed device length. The measured drive voltage is reduced by more than 30 percents, and the crosstalk is also improved by about 4~6 dB.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.7
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• pp.1225-1230
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• 2016

Since a flash light produces enormous amount of photon energy in short time, not only electro-optic and infrared(EO/IR) systems utilized for Intelligence Surveillance Target Acquisition and reconnaissance(ISTAR) activities but also the people of a combat field can be severely influenced by a high flash light bursting in front of them. The people who bumped into a flash could not escape such enormous amount of photon energy, resulting in being blind temporarily or even permanently. In order to investigate the effect of a high flash source on a human eye, it is essential to know how much photon energy be incident into an eye from the flash source. In this paper, the model of irradiated photon energy to individuals from some flashes is proposed. The proposed irradiated photon energy per unit area of retina is based on taking the situation to be modeled as a simple EO system in front of a flash light. The validity of proposed model was proved by the application of the model to human on the surface of the earth with the well known light source, the Sun. The model of this study can be utilized to simulate the retinal intensity and energy of a flash for various conditions such as the illumination levels, the distance from a flash busting site, luminous intensity and time of a flash.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.1406-1408
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• 2003

KOMPSAT-1 (KOrea Multi-Purpose SATellite ? 1) EOC (Electro Optic Camera) raw images are radiometrically corrected on ground based on the characteristics of EOC. They consist of each CCD (Charge?Coupled Device) pixel’s calibration slope which was measured on ground, electrical gains which are applied to amplify for increasing output pixel counts. Currently, radio-metrically corrected EOC images with calibration slope have still shown defective features by residual stripes. So, it should be compensated by adjusting the calibration slope. In this paper, the adjustment of current calibration slope for de-striping EOC images is addressed and test results are shown.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.04a
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• pp.41-42
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• 2006

Carbon nanotubes (CNTs) effects on physical properties of the liquid crystal and twisted nematic (TN) liquid crystal (LC) cells have been investigated. The minute doping of CNTs reduces rotational viscosity of the LC, and thus switching time of the TN cells is improved, especially in grey scale response time. In addition, the dielectric anisotropy and birefringence are not affected by such a small amount of CNT-doping and thus voltage-dependent transmittance remains the same.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.366-367
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• 2006

Different orientated SBN thin films were deposited by Ion Beam Sputtering, and electric properties were measured on each orientation. Ferroelectric $Sr_xBa_{1-x}Nb_2O_6$(SBN) has excellent electro-optic, photo-refractive, piezoelectric, pyroelectric properties. SBN thin film has been deposited by various method, of sol-gel, PLD, CVD, sputtering, etc.. To avoid lead pollution of Pb-system perovskite ferroelectric materials. SBN thin films were fabricated for pyroelectric IR sensor. Using the ceramic target of the same composition and Pt(100)/$TiO_2/SiO-2$/Si(100) substrate, crystallization and orientation behavior as well as electric properties of the films were examined. Seed layer and thin films thickness was controlled to observe the effect on preferred orientation. We measured I-V, C-V, P-E hysteresis to characterize electric-properties on each orientations.

• Korean Journal of Optics and Photonics
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• v.19 no.4
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• pp.320-326
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• 2008

The output characteristics of a laser-diode pumped electrooptic Q-switched Nd:YAG ceramic laser were investigated. The output energy of a Q-switched Nd:YAG ceramic laser was optimized under an output coupler reflectivity of 77%, a laser-diode pulse width of $1,000\;{\mu}s$, and a delay time of $985\;{\mu}s$. The output energy of the Q-switched pulse was measured to be 0.35 mJ with a pulse width of 4 ns under a pump energy of 17.9 mJ. The output efficiency and the peak power were 1.9% and 87.5 kW, respectively.

• Applied Chemistry for Engineering
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• v.18 no.1
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• pp.77-83
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• 2007

It is essential that second order nonlinear optical materials have low optical propagation losses in the wavelengths of second harmonic generation for practical applications in waveguides. Three dipolar chromophores substituted with nitro, cyano, and alkyl sulfone as an electron withdrawing group were prepared. The UV-Vis absorption spectra of the cyano and alkylsulfone chromophores showed a blue-shift compared to the nitro chromophore. The introduction of oxadiazole segment in the chromophore structure led to similar spectral shift. The blue-shift can produce low optical loses at second harmonics. The chromophores were successfully attached to a polyimide, yielding side chain polymers. The nonlinear optical property of the prepared optical polymers was determined by measuring electro-optic coefficient at 1.55 mm. The polymers exhibited high glass transition temperature of over $185^{\circ}C$ and thermal stability to $300^{\circ}C$ through differential scanning calorimeter analysis and thermal gravimetric analysis.

• 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.