• Korean Journal of Optics and Photonics
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• v.30 no.5
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• pp.187-192
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• 2019

In this paper a pump combiner, a key component of a high-power fiber laser, was fabricated, and its output characteristics measured using a high-power performance measuring instrument. The $(18+1){\times}1$ pump combiner consists of an optical-fiber bundle of one signal fiber and 18 pump fibers, an output optical fiber, and housing. The signal and output fibers were fabricated using polarization-maintaining optical fiber. By measuring the loss of signal light along the tapering length of the optical-fiber bundle, the tapering length was optimized to 18 mm. Signal-light insertion loss, pump-light transmittance, and polarization extinction ratio of the fabricated $(18+1){\times}1$ pump combiner were measured as 6.5%, 98.07%, and 18.0 dB respectively. The temperature distribution of the pump combiner, at a high power of 2 kW using 18 pump laser diodes, was measured and analyzed using a thermal-imaging camera.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.6
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• pp.80-85
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• 2019

Vanadium dioxide is a well-known metal-insulator phase transition material. Lots of researches of vanadium redox flow batteries have been researched as large scale energy storage system. In this study, vanadium oxide($VO_x$) thin films were applied to cathode for lithium ion battery. The $VO_x$ thin films were deposited on Si substrate($SiO_2$ layer of 300 nm thickness was formed on Si wafer via thermal oxidation process), quartz substrate by RF magnetron sputter system for 60 minutes at $500^{\circ}C$ with different RF powers. The surface morphology of as-deposited $VO_x$ thin films was characterized by field-emission scanning electron microscopy. The crystallographic property was confirmed by Raman spectroscopy. The optical properties were characterized by UV-visible spectrophotometer. The coin cell lithium-ion battery of CR2032 was fabricated with cathode material of $VO_x$ thin films on Cu foil. Electrochemical property of the coin cell was investigated by electrochemical analyzer. As the results, as increased of RF power, grain size of as-deposited $VO_x$ thin films was increased. As-deposited thin films exhibit $VO_2$ phase with RF power of 200 W above. The transmittance of as-deposited $VO_x$ films exhibits different values for different crystalline phase. The cyclic performance of $VO_x$ films exhibits higher values for large surface area and mixed crystalline phase.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.3
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• pp.443-450
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• 2021

After selecting a PES substrate with excellent thermal stability and optical properties among plastic substrates, a SiO₂ thin film was deposited as a buffer layer to a thickness of 20nm by plasma-enhanced chemical vapor deposition to compensate for the high moisture absorption. Then, the ITZO thin film was deposited by a RF magnetron sputtering method to investigate electrical and optical properties according to RF power. The ITZO thin film deposited at 50W showed the best electrical properties such as a resistivity of 8.02×10^-4 Ω-cm and a sheet resistance of 50.13Ω/sq.. The average transmittance of the ITZO thin film in the visible light region(400-800nm) was relatively high as 80% or more when the RF power was 40 and 50W. Figure of Merits (Φ_TC and FOM) showed the largest values of 23.90×10^-4 Ω^-1 and 5883 Ω^-1cm^-1, respectively, in the ITZO thin film deposited at 50W.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.6
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• pp.250-254
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• 2023

In this study, Li₂O-BaO-Ga₂O₃-TeO₂-TiO₂-GeO₂ glasses with high transmittance in mid-infrared region and high refractive indices were successfully synthesized. The relationship between glass properties and glass composition was analyzed. In Li₂O-BaO-Ga₂O₃-TeO₂-TiO₂-GeO₂ glass system, as increasing TeO₂ concentration, the refractive index increases and the glass transition temperature decreases. In addition, as increasing BaO concentration, the refractive index increases without decrease of Abbe number. The IR-cut off wavelength shifted to the longer wavelength with increasing TeO₂ and BaO contents due to their large molecular weight. The glass transition temperature significantly decreases when BaO was replaced with Li₂O.

• Journal of the Korean Institute of Landscape Architecture
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• v.43 no.5
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• pp.65-73
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• 2015

The purpose of this study was to compare the Mean Radiant Temperature(MRT) under two landscaping shade membranes, white and black, with those of natural outdoor spaces at summer midday. An additional perforated black shading net was applied and compared for the consideration of the practical application. The average MRT at the height of 2.4m, 10cm below the membranes of black, white, and perforated black were $49.1^{\circ}C$, $41.6^{\circ}C$ and $36.8^{\circ}C$ respectively, while that of open sky was $41.8^{\circ}C$. This indicates that a closer position to the darker membrane caused a higher MRT. At the height of 1.1m and 1.7m, the difference of MRT between the black and the white membranes was slight, while the value of white was unexpectedly higher than the black. The MRT of black perforated net showed the lowest value at every height. The black membrane absorbed more solar radiation than the white, which caused the greater release of long wave radiation and higher temperature near the membrane itself. In spite of the higher albedo of the white membrane, the higher solar radiation transmittance rate of which seemed to cause the slightly higher MRT than the black at the hight of 1.1m and 1.7m. In summary, the performance of the black membrane was slightly better than the white in terms of the air conditioning of the human related space around the height of 1.1m and 1.7m, when the shading membranes were at 2.5m height.