• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1995.11a
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• pp.244-247
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• 1995

Physical, electrical and optical properties of Aluminum(Al) thin films were investigated in order to establish the optimum sputtering parameters in mirror reflection films. Al. thin films deposited on corning glass substrate by DC magnetron sputtering were grown as a variation of the input power, operation pressure and deposition time. The properties of the Al thin films have been discussed by deposition rate, SEM, XRD, sheet resistivity, resistivity and reflectance. Al thin films were obtained at the deposition conditions as follows: operating pressure, 3 mtorr; DC input power desnsitiy, 3W/$\textrm{cm}^2$.

• Electrical & Electronic Materials
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• v.9 no.5
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• pp.498-505
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• 1996

In the present work, we have developed the simulator to optimize the process conditions of the AR(antireflection) and HR(high-reflection) coatings for the high power laser diode. The simulator can run on the PC. After making the simple optical model, we establish the Maxwell equations for the model by the operator conversion. By using the Mathematica, we derive a matrix for the multilayer system by applying the equations to the model and optimize the AR and HR coating process conditions by obtaining the reflection rate from the matrix. We also prove the validity of the simulator by comparing the simulation with the characteristics of the laser diode which is AR and HR coated according to the optimized conditions.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1995.11a
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• pp.183-186
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• 1995

The fabrication of dielectric multilayer mirror(DMM) optimized at the wavelength of 1.55$\mu\textrm{m}$ and its spectral properties were investigated. The materials used in the fabrication of DMM are TiO$_2$-SiO$_2$, which have the advantage of yielding high reflectance for relatively small numbers of layers. The optical constants of TiO$_2$single film were obtained by using a modified envelope method. The reflectances of DMMs with 3,7,11 and 23 layers were 58%, 89%, 97% and 99.9% at the wavelength of 1.55$\mu\textrm{m}$, respectively.

• Korean Journal of Optics and Photonics
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• v.14 no.5
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• pp.565-569
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• 2003

We designed a transflective-type LCD using a twisted VA mode. Generally, a VA mode had a blue shift due to intrinsic properties. We solved this problem using spectroscopic compensation film. We used the front scattering film and negative C-plate to improve characteristics of the viewing angle and contrast ratio. As a result, we found that proposed the transflective-type TVA mode had a contrast ratio of about 80:1, a response time of 22 ms, and a reflectance of 25% in comparison with the standard MgO reflector.

• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1346-1348
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• 1998

Tungsten oxide($WO_3$) thin films were prepared by reactive magnetron sputtering in an $Ar/O_2$ atmosphere from a compressed powder $WO_3$ target and their electrochromic(EC) phenomena were investigated. PEO-$LiClO_4$-PC polymer electrolyte can easely be formed into thin films and showed high transmittance. Such electrolyte have electrochromic properties suitable for large-scale electrochromic devices. For the devices using $WO_3$ thin films of 1500, 2500, $4000{\AA}$ thickness with glass/ITO/$WO_3$/PEO-$LiClO_4$-PC/ITO/glass structure, an optical modulation of $50{\sim}60%$ were obtained at a potential range of $1{\sim}2V$. It has shown that transmittance and reflectance of light could be electrically controlled by low applied voltage.

• Current Optics and Photonics
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• v.1 no.6
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• pp.626-630
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• 2017

GaN-based green light-emitting diode (LED) structures suffer from low internal quantum efficiency (IQE), known as the "green gap" problem. The IQE of LED structures is expected to be improved to some extent by exploiting the Purcell effect. In this study, the Purcell effect on the IQE of green LED structures is investigated numerically using a finite-difference time-domain simulation. The Purcell factor of flip-chip LED structures is found to be more than three times as high as that of epi-up LED structures, which is attributed to the high-reflectance mirror near the active region in the flip-chip LED structures. When the unmodified IQE is 20%, the relative enhancement of IQE can be greater than 50%, without utilizing the surface-plasmon coupling effect. Based on the simulation results, the "green gap" problem of GaN-based green LEDs is expected to be mitigated significantly by optimizing flip-chip LED structures to maximize the Purcell effect.

• Journal of Korean Society for Atmospheric Environment
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• v.31 no.6
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• pp.520-529
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• 2015

The ambient $PM_{2.5}$ samples were collected by $PM_{2.5}$ sampler from September 2010 to December 2012 at Daegu University, Gyeongsan. A total of 260 samples were collected and 27 species were analyzed by inductively coupled plasma, ion chromatography, and thermal optical reflectance methods. Factor analysis identified four sources such as biomass burning source/secondary aerosol source, soil source, industry source, and incinerator source/mobile source. Also, backward trajectories were calculated using HYSPLIT 4 (Hybrid single-particle lagrangian integrated trajectory) model and PSCF (Potential source contribution function) model was applied to identify the possible source locations of carbonaceous species and water soluble ions species. PSCF results showed that the possible source locations of most chemical constituents measured in Gyeongsan were the industrial areas in the eastern coast of China, northeast regions of China, the Gobi Desert, and east sea of Korea.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.3
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• pp.261-266
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• 1992

In this paper, we investigated the stability of TeS1100-xTGeS1xT( x = 15,33,50 at. %) thin films by observing the transmittance and reflectance changes with annealing and exposure of diode laser(780nm). As results of transmittance changes in constant tenperature and humidity atmosphere, it was shown that TeS150TGeS150T thin film has the smallest transmittance change. From the XRD patterns, it was confirmed that the transmittance changes in TeS150TGeS150T thin film before and after annealing are due to crystalization. The transmittance changes in TeS150TGeS150T thin film with annealing are largest at diode laser wavelength and the trasmittance changes with laser exposure are decreased fast.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1996.06c
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• pp.171-190
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• 1996

Quality evaluation of agricultural products has been a subject of interest to many researches for many years. As a results, several nondestructive techniques for quality evaluation of agricultural products have been developed. These methods are based on the detection of various physical properties that correlate well with certain quality factors of the products. This paper presents an overview of various quality evaluation techniques that are based on one of the following properties : density, firmness , vibration characteristic , X-ray and gamma ray transmission, optical reflectance and transmission , electrical properties, aromatic volatile emission, and nuclear magnetic resonance (NMR). The sophistication of nondestructive methods has evolved rapidly with modern technologies. The use of various modern image acquisition techniques, such as solid state TV camera, line-scan camera, X-ray scanning , ultrasonic scanning and NMR imaging, in conjunction with image-processing te hniques has provided new opportunities for researchers to develop many new and improved techniques for nondestructive quality evaluation of agricultural products.

• Proceedings of the KSRS Conference
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• 1998.09a
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• pp.89-94
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• 1998

Seasonal variation of attenuation coefficient spectra in Japan sea was extracted from underwater radiance/irradiance spectra observed by a moored buoy system developed by National Space Development Agency of Japan (NASDA). The buoy was deployed 9 months from August 31, 1996 to June 1, 1997. Throughout this period, it was collecting downward irradiance and upward radiance spectra under water at the depth of 1.5m and 6.5m everyday. The dairy averaged diffused attenuation coefficient spectra and underwater reflectance spectra were calculated. The results were compared with the absorption spectra of filtered samples obtained by validation cruises, which carried out 5 times during the moored period. Also, the natural fluorescence of chlorophyll a were extracted from the upward radiance spectra observed at 1.5m depth. The seasonal variation of the calculated attenuation coefficient spectra and the natural fluorescence were examined. The result shows a weak blooming of phytoplankton on November and a large blooming on April.