• Korean Journal of Optics and Photonics
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• v.8 no.2
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• pp.149-153
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• 1997

We demonstrate the operating characteristics(center wavelength, bandwidth, TE/TM polarization, tuning range) of grating-assisted co-directional coupler(GACC) filter fabricated with InGaAsP compound semiconductor. A design of waveguide structure has been focused on the narrow bandwidth characteristics of the filter. Reactive ion etching technique was employed for the uniform waveguide formation. The bandwidths(FWHM) and center wavelengths of the fabricated GACC filter were measured by 1.5 nm and 1530.6 nm for TE polarization and 1.3 nm and 1494.0 nm for TM polarization. This is the one of the narrowest bandwidth at 1530 nm region ever reported. The center wavelength shifted form 1530 nm to 1538 nm when the current of 100 mA was injected at 4.5 mm-long device. Good agreement between the designed and measured operating characteristics for some waveguide structures is demonstrated.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.3 s.357
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• pp.20-25
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• 2007

The periodic domain-inversion in the selective areas of $Ti:LiNbO_3$ Mach-Zender waveguides was performed and band-pass modulators and single sideband (SSB) modulators were fabricated by using domain-reversal. The domain wall velocity was precisely controlled by real-time analysis of a poling-induced response current under an applied voltage. The domain wall velocity was significantly affected by the crystal orientation of the domain wall propagation which influenced the final domain geometry. In a certain case, the decomposition of $LiNbO_3$ crystal was observed, for example, under the condition of too fast domain wall propagation. The fabricated band-pass modulator with a periodic domain-inversion structure showed the maximum modulation efficiency at 30.3 GHz with 5.1 GHz 3dB-bandwidth, and SSB modulator was measured to show 33 dB USB suppression over LSB at 5.8 GHz RF.

• Journal of the Microelectronics and Packaging Society
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• v.20 no.2
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• pp.23-28
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• 2013

Microlens array as basic element of the optical system have been fabricated with various focal length (mainly with long focal length) depending on the purpose of application. In this paper, the microlens arrays were fabricated for observing fluorescent images within sol-gel. Though the fluorescent signal is very low, the microlens array can help obtaining clear images through extracting the fluorescent light from sol-gel. We fabricated microlens arrays with short focal length, which can extract the light using photoresist thermal reflow method. In the experiment, the diameter of microlens decreased after thermal reflow because the solvent within the photoresist was vaporized. Therefore, to compensate the shape error by this reduction, microlens diameter in photomask was altered and spin-coat recipe of photoresist were modified.

• The Journal of Advanced Prosthodontics
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• v.3 no.4
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• pp.196-203
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• 2011

PURPOSE. This study evaluated marginal fit of glass infiltrated alumina cores fabricated using two techniques and their marginal stability after firing cycles of veneering porcelain. MATERIALS AND METHODS. Fifteen standardized all-ceramic crowns were fabricated on a metal die using each technique: slip cast technique of VITA In-Ceram sprint Alumina (Group A as control) and plastic foil matrix technique of Turkom-Cera fused alumina core system (Group B). Copings were compared between groups and within groups at coping stage and after firing each layer of veneering porcelain. A device was used to standardize seating of copings on the metal die and positioning of the specimens under the microscope after each stage of fabrication. The specimens were not cemented and marginal gap was measured using an image analyzing software (Imagepro Express) on the photographs captured under an optical microscope. Two tailed unpaired 't test' was used to compare marginal gaps in two groups and one way ANOVA was used to analyze marginal distortion within each group at 95% confidence interval. RESULTS. The marginal gap was smaller at the coping stage in group B ($60+30{\mu}M$) than group A ($81+21{\mu}M$) with statistical significance. After firing of veneering porcelain the difference was insignificant. At the final stage, both groups exhibited lower mean marginal gaps than at the initial coping stage with the difference of $11.75{\mu}M$ for group A and $11.94{\mu}M$ for group B, but it was statistically insignificant due to high value of standard deviation. CONCLUSION. Within the limitations of this study, it was concluded that both techniques produced copings with comparable and acceptable marginal fit and marginal stability on firing veneering porcelain.

• Korean Chemical Engineering Research
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• v.50 no.6
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• pp.1082-1085
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• 2012

CdTe nanoribbons feature their unique optical properties compared with CdTe nanoparticles. Slow oxidation of tellurium ions on CdTe nanoparticles resulted in the organization of individual nanoparticle into nanoribbons. The light-controlled self-assembly of CdTe nanoparticles led to twisted ribbons. It was found that irradiation improved the oxidation of tellurium ions. Transmission electron microscopy (TEM) were performed to characterize the synthesized nanostructures and showed nanowires were twisted after self-assembly. The photoluminescence was slightly blue-shifted from 550 to 544 nm. This synthetic procedure could potentially provide a key step toward the fabrication of nanowires.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.12B
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• pp.2335-2341
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• 1999

The $2\times32$ coupler consists of Mach-Zehnder interferometer and Y branch coupler. For the designs of this coupler, three dimensional rectangular core waveguide decomposed to two-dimensional structure by the effective index method. To optimize the waveguide structure, the confinement factor was investigated with two-dimensional finite difference Beam Propagation Method. The $2\times32$ coupler fabricated by simulation with height between Mach-Zehnder arms, H=$43.6\mu\textrm{m}$(path difference $0.668\mu\textrm{m}$) was showed best characteristics. In the results of dry etching of core layer, the etching rate of core layer was above 2600${\AA}$/min, the etching ratio of SiO2 to Al mask was 30:1 and the uniformity of etching was $\pm$5%. The maximum insertion loss and the uniformity of $2\times32$ coupler were below 19.2dB, 2dB respectively.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.5
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• pp.229-234
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• 2017

In this study, TiAl alloy was fabricated by a centrifugal casting method for turbo charge of automotive. Optimum conditions for defectless morphology using various ceramic mold were investigated. The crystal structure, microstructure, and chemical composition of the TiAl prepared by centrifugal casting were studied by X-ray diffractometer (XRD), optical microscopy (OM), field emission scanning electron microscopy (FE-SEM) and energy dispersive spectroscopy (EDS), microvickers hardness analyzer (HV). Two kinds of dendrite structures were observed with 4-fold and 6-fold symmetries. The FE-SEM, EDS and HV examinations of the as-cast TiAl showed that the thickness of the oxide layer (${\alpha}$-case) was typically less than $50{\mu}m$.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.1
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• pp.191-196
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• 2010

Aluminum doped zinc oxide (AZO) films have been prepared on Coming 7059 glass substrates by r.f. magnetron sputtering method. A powder target instead of a conventional sintered ceramic target was used in order to improve the utilization efficiency of the target and reduce the cost of the film deposition process. The influence of sputter pressure on the structural, electrical, and optical properties of AZO films were studied. The AZO films had hexagonal wurtzite structure with a preferred c-axis orientation, regardless of sputter pressure and target types. The crystallinity and degree of orientation was increased by increasing the sputter pressure. For higher sputtering pressures, a reduction of the resistivity was observed due to a increase on the mobility and the carrier concentration. The lowest resistivity of $6.5{\times}10^{-3}\;{\Omega}-cm$ and the average transmittance of 80% can be obtained for films deposited at 15 mTorr.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.67-67
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• 2008

Application of organic materials with low cost, easy fabrication and advantages of flexible device are increasing attention by research work. Recently, one of them, organic solar cells were rapidly increased efficiency with regioregular poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyricacidmethylester (PCBM) used typical material. To increased efficiency of organic solar cell has tried control of domain of PCBM and crystallite of P3HT by thermal annealing and solvent vapor annealing. [4-6] In those annealing effects, be made inefficiently efficiency, which is increased fill factor (FF), and current density by phase-separated morphology with blended P3HT and PCBM. In addition, increased conductivity by modified hole transfer layer (HTL) such as Poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS), increased both optical and conducting effect by titanium oxide (TiOx), and changed cathode material for control work function were increased efficiency of Organic solar cell. In this study, we had described effect of organic photovoltaics by conductivity of interlayer such as PEDOT:PSS and TCO (Transparent conducting oxide) such as ITO, which is used P3HT and PCBM. And, we have measured with exactly defined shadow mask to study effect of solar cell efficiency according to conductivity of hole transfer layer.

• Journal of IKEEE
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• v.23 no.4
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• pp.1128-1133
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• 2019

This paper proposed colored front panel glass for Building Integrated Photovoltaic (BIPV) systems using multi-layered thin films composed of transition metal oxide (TMO) layers. Molybdenum oxide (MoO₃) and tungsten oxide (WO₃) provided complementary and suitable materials in making effective interference of reflected light from interfaces with significant difference in refractive indices. A simple, fast, and cheap fabrication method was achieved by depositing the multi-layer films in a single thermal evaporator. Magenta colored glass with optical transmittance of more than 90% was achieved with MoO₃ (60nm)/WO₃(100nm) multi-layered film. This technology could play in a critical role in commercial BIPV system applications.