• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.9
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• pp.802-807
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• 2007

We have developed red phosphorescent top emission organic light-emitting diodes with transparent metal cathodes deposited by using thermal evaporation technique. Phosphorescent guest molecule, BtpIr(acac), was doped in host CBP for the red phosphorescent emission, Ca/Ag, Ba/Ag, and Mg/Ag double layers were used as cathode materials of top emission devices, which were composed of glass/Ni/2TNATA(15 nm)/${\alpha}$-NPD(35 nm)/CBP:BtpIr(acac)(40 nm, 10%)/BCP(5 nm)/$Alq_3$(5 nm)/cathodes. The optical transparencies of these metal cathodes strongly depend on underlying Ca, Ba, and Mg layers. These layers also strongly affect the electrical conduction and emission properties of the red phosphorescent top emission devices.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.769-772
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• 2008

For several years, many researchers have proposed LED backlight dimming technology for low power consumption and high contrast ratio. One of the major issues plaguing RGB LED with 2D dimming technology is color shift. This undesirable variation makes it difficult to use RGB LED as light sources in the backlight system. This paper describes the useful method of the optical feedback system for 2D dimming RGB LED backlight. The test results show that our proposed method is very suitable for the 2D dimming technology.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.521-522
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• 2006

In this paper, hybrid air-water discharges were used to develop an optimal condition for providing a high level of water decomposition for hydrogen yield. Electrical and optical phenomena accompanying the discharges were investigated along with feeding gases, flow rates, and point-to-plane electrode gap distance. The primary focus of this experiment was put on the optical emission of the near UV range, with the energy threshold sufficient for water dissociation and excitation. The $OH(A^{2+},'=0\;X^2,"=0$) band's optical emission intensity indicated the presence of plasma chemical reactions involving hydrogen formation. In the gaseous atmosphere saturated with water vapor the OH(A-X) band intensity was relatively high compared to the liquid and transient phases although the optical emission strongly depended on the flow rate and type of feeding gas. In the gaseous phase discharge phenomenon for Ar carrier gas transformed into a gliding arc via the flow rate growth. OH(A-X) band's intensity increased according to the flow rate or residence time of He feeding gas. Reciprocal tendency was acquired for $N_2$ and Ar carrier gases. The peak value of OH(A-X) intensity was observed in the proximity of the water surface, however in the cases of Ar and $N_2$ with 0.5 SLM flow rate peaks shifted to the region below the water surface. Rotational temperature ($T_{rot}$) was estimated to be in the range of 900-3600 K, according to the carrier gas and flow rate, which corresponds to the arc-like-streamer discharge.

• Korean Journal of Optics and Photonics
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• v.29 no.1
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• pp.32-39
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• 2018

The impact of the amplified spontaneous emission (ASE) on the gain recovery time of a bulk semiconductor optical amplifier (SOA) is investigated. The gain-recovery time is obtained by determining the time evolution of the gain, carrier density, and ASE in an SOA, after the propagation of a short pump pulse and continuous-wave (CW) probe of gain dynamics. In the simulation, a wide-band-semiconductor model, which can be characterized by the material gain coefficient over a wide wavelength range, is used, because the gain bandwidth of a practical SOA is very wide. The pump pulse and counterpropagating CW probe field are considered in the simulation, with the ASE noise spectrum equally divided.

• Proceedings of the Optical Society of Korea Conference
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• 1999.08a
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• pp.184-185
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• 1999

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.161-164
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• 2002

Optical fiber vibrations sensors (OFVSs) and extrinsic Fabry-Perot interferometer (EFPI) were used in damage monitoring of fiber-metal laminates(FML). The optical fiber vibration sensor and EFPI were applied in order to detect and evaluate the strain, damage and failure of FML. Damages in composites, such as matrix cracks, delamination and fiber breakage may occur as a result of excessive load, fatigue and low-velocity impacts. Tensile test was performed with the measurement of optical signal and acoustic emission (AE). The signals of the optical fiber vibration sensor due to damages were quantitatively evaluated by wavelet transform. EFPI was less sensible to the damage signals compared with the optical fiber vibration sensor. It was found that damage information of comparable in quality to acoustic emission data could be obtained from the optical fiber vibration sensor signals.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2009.10a
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• pp.235-236
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• 2009

본 연구에서는 Optical emission spectroscopy (OES)에 CUSUM과 전문가 시스템을 이용하여 플라즈마를 감시하는 기법을 개발하였다. CUSUM과 Dempster-Shafer를 이용하여 고장에 민감한 OES파장을 추출하였으며, 추출된 파장은 플라즈마 감시에 이용될 것으로 기대된다.

• Proceedings of the Optical Society of Korea Conference
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• 2002.11a
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• pp.152-153
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• 2002

• Journal of the Optical Society of Korea
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• v.15 no.4
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• pp.407-414
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• 2011

We analyze the cooperative spontaneous emission of optically excited nanocrystals into surface plasmon polaritons propagating on the surface of a cylindrical metallic nanowire. The spontaneous emission probability of the nanocrystals is obtained by perturbative expansions with and without dipole-dipole interaction among nanocrystals in order to see the cooperative effects. The spontaneous emission probability depends on the radial and axial distributions, as well as on the dipolar orientation of nanocrystals. It is shown that the spontaneous emission probability is strongly influenced by dipole-dipole interaction, axial distribution, and dipolar orientation of nanocrystals for closely spaced nanocrystals.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.171-174
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• 2000

This study uses neon and xenon gas mixture discharges to determine the effects of the neon plasma emission on the characteristics of visible emission from the stimulation of the red, green, blue(RGB) phosphor layers in a surface-type alternate current plasma display panel(AC PDP). With a mixture of less than 2% xenon to neon, it is found that the luminance changes in the visible emission of the phosphor layers are similar to those of the neon plasma emission. In the range of xenon mix ratio from 2 to 5%, the luminance of the red, green, blue(RGB) phosphor layers decreases with a decrease in the neon plasma emission intensity. However, with a mixture of above 5% xenon to neon, the luminance of the red, green, blue(RGB) phosphor layers increases regardless of a decrease in the neon plasma emission intensity. Furthermore, the color purity of the red, green, blue(RGB) phosphor layers improve as the neon plasma emission intensity decreases. Accordingly, it is concluded that the optical properties of the phosphor layers, including color purity and luminance, depend on the neon plasma discharge emission as well as the visible emission from the stimulation of the phosphor layers.