• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1454-1456
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• 2007

The electrical and the optical properties of blue organic light-emitting devices (OLEDs) with a multiple emitting layer (EML) acting as electron and hole trapping layers were investigated. While the luminance efficiency of the OLEDs with a multiple EML was very stable, regardless of variations in the applied voltage.

• Proceedings of the Optical Society of Korea Conference
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• 2003.02a
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• pp.224-225
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• 2003

Since group velocity (GV) mismatch significantly limits the efficiency of nonlinear interactions such as second harmonic generation (SHG), several techniques have been developed to compensate GV mismatch. The simplest way to avoid the GV mismatch problem is to reduce the device length. However, it results in a poor trade-off between the SHG spectral bandwidth and the conversion efficiency. (omitted)

• ETRI Journal
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• v.30 no.6
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• pp.833-843
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• 2008

The effect of forward and reverse electrostatic discharge (ESD) on the electro-optical characteristics of oxide vertical-cavity surface-emitting lasers is investigated using a human body model for the purpose of understanding degradation behavior. Forward ESD-induced degradation is complicated, showing three degradation phases depending on ESD voltage, while reverse ESD-induced degradation is relatively simple, exhibiting two phases of degradation divided by a sudden distinctive change in electro-optical characteristics. We demonstrate that the increase in the threshold current is mainly due to the increase in leakage current, nonradiative recombination current, and optical loss. The decrease in the slope efficiency is mainly due to the increase in optical loss.

• Current Optics and Photonics
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• v.1 no.3
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• pp.239-246
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• 2017

A compact plasmonic switching scheme, based on the phase change of a thin-film chalcogenide material ($Ge_2Sb_2Te_5$), is proposed and numerically investigated at optical-communication wavelengths. Surface plasmon polariton modal analysis is conducted for various thicknesses of dielectric and phase-change material layers, and the optimized condition is induced by finding the region of interest that shows a high extinction ratio of surface plasmon polariton modes before and after the phase transition. Full electromagnetic simulations show that multiple reflections inside the active region may conditionally increase the overall efficiency of the on/off ratio at a specific length of the active region. However, it is shown that the optimized geometrical condition, which shows generally large on/off ratio for any length of active region, can be distinguished by observing the multiple-reflection characteristic inside the active region. The proposed scheme shows an on/off switching ratio greater than 30 dB for a length of a few micrometers, which can be potentially applied to integrated active plasmonic systems.

• Journal of the Optical Society of Korea
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• v.16 no.3
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• pp.270-276
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• 2012

An off-axis integral floating system using a concave mirror is analyzed to resolve the image distortion incurred by the off-axis optical arrangement. The concave mirror can be adopted as the floating device to improve the optical efficiency. The image distortion due to the tilting axis of the concave mirror needs to be analyzed precisely to generate the pre-distortion image. In this paper, we calculate the image deformation in the off-axis structure of the concave mirror using the geometrical optics. Using the calculation results, the compensated elemental image can be generated for the pre-distortion integrated image, which can be projected to the floating 3D image without image distortion. The basic experiments of the off-axis integral floating are presented to prove and verify the proposal.

• Korean Journal of Optics and Photonics
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• v.30 no.4
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• pp.146-153
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• 2019

The exposure system is a device that transfers a circuit pattern to a desired location. To display patterns on a substrate without deforming the optical characteristics, the characteristics of the optical exposure system are very important. Therefore, to form a microcircuit pattern, a small divergence angle should impinge on the irradiation area. Also, since the light from the source must react uniformly with the photosensitizer, it must have high luminance efficiency and uniformity of illumination. In this paper a parabolic reflector and an aspherical lens were designed to solve the problem of narrow-angle implementation, and it was confirmed by simulation analysis after their arrangement that the beam angle, uniformity, and maximum illuminance satisfied the target performance.

• Journal of the Microelectronics and Packaging Society
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• v.10 no.2
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• pp.33-37
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• 2003

The new textured surface epitaxial base(TSEB) cell as a high efficiency Si solar cell was fabricated and its eletro-optical characteristics were investigated. The fabricated device showed the open circuit voltage of 0.62 V, the short circuit current of 40 mA, the fill factor of 0.7, and the efficiency of 16% under the incident light of AM-1 100 mW/$cm^2$. The TSEB cell proposed in this paper has the structural superiority in the fabrication of high efficiency solar cell due to the carrier drift transport in the optical absorption region and the formation of back surface field by $P^-/P^+$ epitaxial base, and the low emitter series resistance by insertion of $n^+$ buried contact.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1575-1577
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• 2002

In this study, multi layer type OLED(Organic Light Emitting Diode) has been fabricated using $Snq_2$, $Snq_4$, and $Alq_3$ for development of high efficiency, electrical and optical properties of multi layer type OLED investigated. The HTL(Hole Transfer Layer) and EML(Emitting Material Layer) were fabricated by using vacuum evaporation on ITO electrode, and its thickness controlled using thickness monitor. Al was used as a cathode. The electrical and optical properties such as J-V, brightness-V and EL spectrum of OLED device was measured using I.V.L.T system. The result, brightness of $Alq_3$, $Snq_2$ and $Snq_4$ were $3900cd/m^2$, $63cd/m^2$ and $23cd/m^2$ respectively.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.186-186
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• 2006

We report a new architecture for high efficiency polymer solar cells introducing a new concept of 'optical spacer' with new material. By implementing a novel solution-based titanium oxide ($TiO_{x}$) layer between the active layer and the electron collecting Al electrode, we invented a way to increase ${\sim}50\;%$ in power conversion efficiency compared to conventional polymer solar cells. Now the new devices exhibit ${\sim}6\;%$ power conversion efficiency, which is the highest value reported to date for a polymer based photovoltaic cell. The $TiO_{x}$ layer increases the efficiency by modifying the spatial distribution of the light intensity inside the device, thereby creating more photogenerated charge carriers in the bulk heterojunction layer.

• Journal of the Korean Vacuum Society
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• v.16 no.5
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• pp.371-376
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• 2007

We have investigated the lasing characteristics of the InGaAs quantum dot laser diode (QD-LD) and InGaAs quantum well laser diode (QW-LD) operated at the 980 nm wavelength range. The 980-nm lasers are used as a pumping source for a erbium-doped fiber amplifier (EDFA) and it shows high efficiency in long-haul optical fiber network. We have compared the threshold current density, the characteristic temperature, the optical power and the internal efficiency of QD-LD and QW-LD under a pulsed current condition. The QD-LD shows superior performances to the QW-LD. Further optimization of a LD structure is expected to the superior performances of a QD-LD.