• Korean Journal of Optics and Photonics
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• v.15 no.5
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• pp.449-454
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• 2004

The optical limiter is an optical component which reduces laser beam intensity for the protection of eyes and light sensors. Carbon nanotube is now known as a highly efficient optical limiting material. Optical limiting effect of the multi-walled carbon nanotube suspensions, in several kinds of solvents such as distilled water, chloroform, ethanol and ethylene glycol, were measured in the range from room temperature to near to the boiling points of the solvents. The pulsed Nd:YAG laser whose wavelength is 1064 nm and pulse duration is 6 ns was used as a light source. The experimental result shows that the limiting efficiency was reduced as the temperature increased, and the suspension which has lower boiling point, viscosity and surface tension has highest efficiency.

• Korean Journal of Optics and Photonics
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• v.24 no.6
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• pp.297-310
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• 2013

With the explosive growth of internet data traffic due to the FTTH penetration, prevalence of smart devices and cloud network service, the demand for higher bandwidth is ever increasing with the pace of more than 40% annual growth. To accommodate ultra high bandwidth traffic, optical components in each hierarchy have progressed rapidly. WDM has begun to be deployed along with higher bandwidth service in the access network. Next-generation ROADM is under development for efficient network management in the metro network. For long-haul transmission, an advanced modulation scheme based on coherent transmission technology has been adopted to enhance spectral efficiency. In this paper, core components to meet the demands of high speed, high efficiency and low power consumption will be reviewed.

• Journal of the Optical Society of Korea
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• v.2 no.1
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• pp.13-21
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• 1998

Based on the escape cone concepts, high-brightness light-emitting diodes (LEDs) have been analyzed. In AlGaAs or InGaAlP LEDs, photon absorption in the ohmic region under the electrode is known to be significant. Thus, ins general, a thick window layer (WL) and a transparent substrate (TS) would minimize photon shielding by the electrodes and considerably improve photon output coupling efficiency. However, the schemes do not seem to be necessary in InGaN system. Photon absorption in ohmic contact to a wide bandgap semiconductor such as GaN may be negligible and, as a result, the significant photon shielding by the electrodes will not degrade the photon output coupling efficiency so much. The photon output coupling efficiency estimated in InGaN LEDs is about 2.5 - 2.8 times that of the conventional high-brightness LED structures based on both WL and TS schemes. As a result, the extenal quantum efficiency in InGaN LEDs is as high as 9% despite the presumably very low internal quantum efficiency.

• Korean Journal of Optics and Photonics
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• v.26 no.2
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• pp.98-102
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• 2015

The radiative quantum efficiency of a solid-state laser was measured by photoacoustic spectroscopy with a PZT as the detector. The radiative quantum efficiency was about 58.3 % for a laser-diode pumped Nd:S-VAP laser under lasing conditions. The measurement of radiative quantum efficiency was presented as an effective method for the optimization of a laser resonator.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.5
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• pp.325-330
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• 2017

We fabricated 1-D and 2-D diffraction gratings of SiOx anti-reflection (AR) film grown on a quartz substrate and integrated them into a c-Si photovoltaic (PV) submodule. The light-trapping effect of the resulting submodules was studied in terms of the oblique optical incident angle, ${\theta}_i$. As the ${\theta}_i$ increased, solar conversion efficiency, ${\eta}$, was improved as expected by the increased optical transmission caused by the grating. For ${\theta}_i{\leq}30^{\circ}$, the relative solar conversion efficiency, ${\Delta}{\eta}$, of a 1-D SiOx (t=300 nm) grating, compared to that of a flat SiOx AR-coated integrated PV submodule, was improved very little, with a small variation of within 2%, but increased markedly for ${\theta}_i{\geq}40^{\circ}$. We observed a change of ${\Delta}{\eta}$ as large as 10.7% and 9.5% for the SiOx grating of period t=800 nm and 1200 nm, respectively. For a 2-D SiOx (t=300 nm) grating integrated PV submodule, however, the optical trapping behavior was similar in terms of ${\theta}_i$ but its variation was small, within ${\pm}1.0%$.

• Proceedings of the Optical Society of Korea Conference
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• 2008.07a
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• pp.321-322
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• 2008

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.361-364
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• 2004

Polarizers with high polarizing efficiency and other advanced optical films based on Lyotropic Dichroic Dyes have been developed for LCD and other applications. The developed optical films reveal both rod-like chromophores structure in a case of positive, or O-films and disc-like one for negative, or E-film.

• ETRI Journal
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• v.45 no.6
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• pp.1056-1064
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• 2023

The optical properties of the materials composing organic light-emitting diodes (OLEDs) are considered when designing the optical structure of OLEDs. Optical design is related to the optical properties, such as the efficiency, emission spectra, and color coordinates of OLED devices because of the microcavity effect in top-emitting OLEDs. In this study, the properties of top-emitting blue OLEDs were optimized by adjusting the thicknesses of the thin metal layer and capping layer (CPL). Deep blue emission was achieved in an OLED structure with a second cavity length, even when the transmittance of the thin metal layer was high. The thin metal film thickness ranges applicable to OLEDs with a second microcavity structure are wide. Instead, the thickness of the thin metal layer determines the optimized thickness of the CPL for high efficiency. A thinner metal layer means that higher efficiency can be obtained in OLED devices with a second microcavity structure. In addition, OLEDs with a thinner metal layer showed less color change as a function of the viewing angle.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.663-665
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• 2004

Ethernet-based passive optical network(EPON) technology is being considered as a promising solution for next-generation broadband access network. It must have the property of high efficiency, low cost, and support quality of service(QoS). A major feature for this new architecture is the use of a shared transmission media between all connected optical network unit(ONU). Hence, medium access control(MAC) arbitration mechanisms are essential for the successful implementation of EPON. In this paper we propose a simple dynamic bandwidth allocation(DBA) algorithm that improves the performance of network and supports IP-based multimedia applications with the bursty data traffic. In addition, we introduce analytic models of proposed algorithms and prove the system based on our algorithm to be asymptotically stable. Simulation results show the new DBA algorithm provides high bandwidth efficiency and low queueing delay of ONU in EPON.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.840-843
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• 2004

UV molding is a process for integrating micro/nano polymeric optical components on optoelectronic modules. In the present study, a microlens array for vertical cavity surface emitting laser(VCSEL) to fiber coupling was designed, integrated and tested. At the design stage, design variables ware optimized to maximize the coupling efficiency, and tolerance analysis was carried out. At the integration stage, the UV transparent mold was fabricated and the microlens array on VCSEL array was integrated by UV molding process. Finally the coupling efficiency of VCSEL to fiber was measured and analyzed.