• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.6
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• pp.1369-1375
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• 2007

The recent, a large capacity of telecommunication networks is required in order to it is in proportion to capacity of information communication increase and to satisfy a demand because of the demand about Internet, a multimedia service of internet, Video of internet protocol(VoIP), Audio/Video streaming. As a result, DWDM(Dense Wavelength Division Multiplexing)technologies are emerging to be a prevailing the method of solving it without additional optical fiber network building and high-speed equipment. Therefore this thesis proposed the optical filter of fiber/multilayer slab coupled structure combining it to multilayer slab waveguide by polishing the cladding of one side of fiber to design the optical filter having these functions. When a separation distance of fiber and slab was $3{\mu}m$, The optical filter proposed as the simulation result was satisfied with a DWDM filter characteristic with FWHM of 0.1nm on TM mode and TE mode as 32nm polarization independence in a communication window of $1.3{\mu}m$ when center wavelength was each ${\lambda}_0=1.274755{\mu}m$ and ${\lambda}_0=1.30591{\mu}m$.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.7
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• pp.1359-1366
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• 2007

The recent, a large capacity of communication is required in order to it is in proportion to capacity of information communication increase and to satisfy a demand because of the demand about Internet, a multimedia service of Video of internet protocol(VoIP), Audio/Video steaming. DWDM(Dense Wavelength Division Multiplexing) technique has been emerged as the method of solving it without additional optical fiber network building and hish-speed equipment. Therefore this thesis proposed the optical filter of fiber/multilayer slab coupled structure combining it to multilayer slab waveguide by polishing the cladding of one side of fiber to design the optical filter having these functions. The optical filter proposed as the simulation result satisfies DWDM filter characteristic; 1) when the separation distance between fiber and slab is $4.15{\mu}m$ at the communication window of $1.5{\mu}m$, the polarization independence is 65nm, 2) when the center wavelengths about TM mode and TE mode are each ${\lambda}_0=1.54946\;{\mu}m$ and ${\lambda}_0=1.6144\;{\mu}m$ and, FWHM(Full at Half Maximun) is 0.1nm.

• Applied Chemistry for Engineering
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• v.33 no.1
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• pp.50-57
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• 2022

Ti-In-Zn-O (TIZO)/Ag/TIZO multilayer transparent electrodes were prepared on glass substrates at room temperature using RF/DC magnetron sputtering. Obtained multilayer structure comprising TIZO/Ag/TIZO (10 nm/10 nm/40 nm) with the total thickness of 60 nm showed a transmittance of 86.5% at 650 nm and a sheet resistance of 8.1 Ω/□. The multilayer films were expected to be applicable for use in energy-saving smart window based on polymer-dispersed liquid crystal (PDLC) because of their transmittance properties to effectively block infrared rays (heat rays). We investigated the effects of the content ratio of prepolymer, the thickness of the PDLC coating layer, and the ultraviolet (UV) light intensity on electro-optical properties, and the surface morphology of polyester acrylate-based PDLC systems using new TIZO/Ag/TIZO transparent conducting electrodes. A PDLC cell with a thickness of 15 ㎛ PDLC layer photocured at an UV intensity of 1.5 mW/cm² exhibited good driving voltage, favorable on-state transmittance, and excellent off-haze. The LC droplets formed on the surface of the polymer matrix of the PDLC composite had a size range of 1 to 3 ㎛ capable of efficiently scattering incident light. Also, the PDLC-based smart window manufactured using TIZO/Ag/TIZO multi-layered transparent electrodes in this study exhibited a light brown, which will have an advantage in terms of aesthetics.

• Bulletin of the Korean Chemical Society
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• v.33 no.5
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• pp.1647-1652
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• 2012

With the objective to design and synthesis of Schiff's base symmetrical liquid crystal dimmers and to study the effect of molecular structure variation ($o-ortho$, $m-meta$, $p-para$) and change in alkoxy terminal chain length on mesomorphic properties of liquid crystals, We have synthesized Schiff base dimers from dialdehyde derivative containing 2-hydroxy-1,3-dioxypropylene as short spacer with aniline derivatives having different lengths of terminal alkoxy chains ($n$ = 5, 7, 9). The chemical structure of the final products was characterized by proton nuclear magnetic resonance ($^1H$ NMR) spectroscopy and fourier transform infrared (FT-IR) spectroscopy. The mesomorphic properties and optical textures of the resultant dimers were characterized by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The existence of smectic A phase transition was confirmed by the observation of batonnets and fan shaped textures in optical microscopy when compound were heated from crystalline phase. All of the dimers of this series, with the exception of $\mathbf{2S_5}$ -ortho, -meta, -para, were thermotropic liquid crystal. The compound $\mathbf{2S_9}$ -meta was monotropic, while the rest were enantiotropic. It was found that the change in terminal alkoxy chain length has pronounced effect on the mesomorphic properties. The temperature range of smectic A phase window widens with increasing alkoxy chain length.

• Journal of Sensor Science and Technology
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• v.6 no.2
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• pp.163-171
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• 1997

CdS thin films for window material of solar cell were prepared by close spaced vapor transport deposition system and annealed at different temperatures. The structural, electrical, and optical properties of as-deposited and annealed CdS films were investigated as functions of substrate and annealing temperatures. The CdS thin films were grown perpendicularly to the substrate along the (002)plane with hexagonal structure regardless of the preparation conditions The resistivity of the CdS film deposited was increased gradually from $60{\Omega}cm$ for $25^{\circ}C$ to $2{\times}10^{4}{\Omega}cm$ for $300^{\circ}C$. The optical transmittance at the substrate temperature of $25^{\circ}C$ was about 80% in the the visible spectrum. The resistivity increased monotonically, and the optical transmittance was decreased substantially with annealing temperature due to the increased defect density in the CdS film.

• Publications of The Korean Astronomical Society
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• v.20 no.1 s.24
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• pp.151-161
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• 2005

The reimaging optics of the KASINICS (KASI Near Infrared Camera System) includes many transparent components like an entrance window, band-pass filters, and blocking filters. As observational targets or in-field background objects, bright stars may cause optical ghosts that can significantly degrade the system performance of the KASINICS. We estimated analytically the relative brightness of ghost components with respect to a point source and examined the effects of tilting optical components as a method of suppressing ghosts. We also performed numerical ray tracings including all the optical components and found the results are consistent with those of the analytic estimations. We conclude that the KASINICS will not suffer from significant ghost effects with appropriate anti-reflection coatings and fittings for the optical components.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.109-109
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• 2010

$Er^{3+}$ ion shows a stable and efficient luminescence at 1.54mm due to its $^4I_{13/2}\;{\rightarrow}\;^4I_{15/2}$ intra-4f transition. As this corresponds to the low-loss window of silica-based optical fibers, Er-based light sources have become a mainstay of the long-distance telecom. In most telecom applications, $Er^{3+}$ ions are excited via resonant optical pumping. However, if nanocluster-Si (nc-Si) are co-doped with $Er^{3+}$, $Er^{3+}$ can be excited via energy transfer from excited electrical carriers in the nc-Si as well. This combines the broad, strong absorption band of nc-Si with narrow, stable emission spectra of $Er^{3+}$ to allow top-pumping with off-resonant, low-cost broadband light sources as well as electrical pumping. A widely used method to achieve nc-Si sensitization of $Er^{3+}$ is high-temperature annealing of Er-doped, non-stoichiometric amorphous thin film with excess Si (e.g.,silicon-rich silicon oxide(SRSO)) to precipitate nc-Si and optically activate $Er^{3+}$ at the same time. Unfortunately, such precipitation and growth of nc-Si into Er-doped oxide matrix can lead to $Er^{3+}$ clustering away from nc-Si at anneal temperatures much lower than ${\sim}1000^{\circ}C$ that is necessary for full optical activation of $Er^{3+}$ in $SiO_2$. Recently, silicon-rich silicon nitride (SRSN) was reported to be a promising alternative to SRSO that can overcome this problem of Er clustering. But as nc-Si formation and optical activation $Er^{3+}$ remain linked in Er-doped SRSN, it is not clear which mechanism is responsible for the observed improvement. In this paper, we report on investigating the effect of separating the nc-Si formation and $Er^{3+}$ activation by using hetero-multilayers that consist of nm-thin SRSO or SRSN sensitizing layers with Er-doped $SiO_2$ or $Si_3N_4$ luminescing layers.

• Korean Journal of Materials Research
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• v.21 no.12
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• pp.697-702
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• 2011

Two-dimensional (2D) nano patterns including a two-dimensional Bravais lattice were fabricated by laser interference lithography using a two step exposure process. After the first exposure, the substrate itself was rotated by a certain angle, $90^{\circ}$ for a square or rectangular lattice, $75^{\circ}$ for an oblique lattice, and $60^{\circ}$ for a hexagonal lattice, and the $90^{\circ}$ and laser incident angle changed for rectangular and the $45^{\circ}$ and laser incident angle changed for a centered rectangular; we then carried out a second exposure process to form 2D bravais lattices. The band structure of five different 2D nano patterns was simulated by a beam propagation program. The presence of the band-gap effect was shown in an oblique and hexagonal structure. The oblique latticed ZnO nano-photonic crystal array had a pseudo-bandgap at a frequency of 0.337-0.375, 0.575-0.596 and 0.858-0.870. The hexagonal latticed ZnO nano-crystallite array had a pseudo-bandgap at a frequency of 0.335-0.384 and 0.585-0.645. The ZnO nano structure with an oblique and hexagonal structure was grown through the patterned opening window area by a hydrothermal method. The morphology of 2D nano patterns and ZnO nano structures were investigated by atomic force microscopy and scanning electron microscopy. The diameter of the opening window was approximately 250 nm. The height and width of ZnO nano-photonic crystals were 380 nm and 250 nm, respectively.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.8
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• pp.563-569
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• 1999

Boron doped CdS films were prepared by chemical bath deposition using boric acid$(H_3BO_3)$ as donor dopant source, and their electrical, optical properties were investigated as a function of doping concentration. In addition, effects of boron doping of CdS films on characteristics of CdS/CdTe solar cells were investigated. Boron doping highly decreased the resistivity and slightly increased optical band gap of CdS films. The lowest value of resistivity was $2 \Omega-cm \;at\; H_3BO_3/Cd(Ac)_2$ molar ratio of 0.1. For the molar ratio more than 0.1, however, the resistivity increased because of decreasing carrier concentration and mobility and showed similar value for undoped films. The photovoltaic characteristics of CdS/CdTe solar cells with boron doped CdS film improved due to the decrease of the conduction band-Fermi level energy gap of CdS films and the series resistance of solar cell.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.410.1-410.1
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• 2016

Vanadium dioxide ($VO_2$) is a well-known material that exhibits a metal-semiconductor transition at 340 K, with drastic change of transmittance at NIR region. However, $VO_2$ based thermochromics accompany with low visible transmittance value and unfavorable color (brownish yellow). Herein, we demonstrate the adjustment of visible transmittance of $VO_2$ thin film by nanosphere template assisted patterning process using sol-gel method. 2-Dimenstional honeycomb shape was varied as function of diameter of nanosphere and coating conditions. The morphological geometry of the films was investigated by FE-SEM and AFM. Result shows that inversed shape of nanosphere was formed clearly and pattern width was altered according to the bead size. This structure creates the geometrical blank area from the position of nanosphere which improves the optical transmittance at the visible region. Moreover, such patterned $VO_2$ thin film not only maintains the optical switching efficiency, but also generate the gorgeous scattering effect which presumably support the glazing application.