• Korean Journal of Optics and Photonics
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• v.34 no.6
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• pp.225-234
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• 2023

Mode-locked pulse lasers have a temporal periodicity up over a short period of time. However, in the time-frequency domain, a pulsed laser with temporal periodicity is described as an optical frequency comb with constant frequency spacing. Each frequency component of the optical frequency comb in the frequency domain is then a continuous-wave (CW) laser with hundreds of thousands of single-frequency-component CW lasers in the time domain. This optical frequency comb was developed approximately 20 years ago, enabling the development of the world's most precise atomic clocks and precise transmission of highly stable optical frequency references. In this review, research on the selective extraction of the single-frequency components of optical frequency combs and the control of the frequency components of optical combs is introduced. By presenting the concepts and principles of these optical frequency combs in a tutorial format, we hope to help readers understand the properties of light in the time-frequency domain and develop various applications using optical frequency combs.

• Proceedings of the Optical Society of Korea Conference
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• 2002.07a
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• pp.254-255
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• 2002

Optical elements such as small glass lenses or optical fibers can be permanently bonded to substrates using Al inter-layer by applying Pressure and heating. As an example aspherical lens was bonded on a silicon V-groove. The bonding has high shear strength and good thermal cycling stability.

• Journal of the Optical Society of Korea
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• v.7 no.1
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• pp.13-19
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• 2003

The effects of strain distribution in quantum wire arrays have been analyzed using a finite-element method including both the hydrostatic and shear strain components. Their effects on the optical properties of the quantum wire arrays are assessed for various types of stress profiles by calculating the optical gain and the polarization dependence. The results show unique polarization dependency, which can be exploited either for the single polarization or the polarization-independent operation in quantum wire photonic devices.

• Journal of the Optical Society of Korea
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• v.15 no.1
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• pp.4-8
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• 2011

We have evaluated the performances of bidirectional optical amplifiers which were suited for the cost-effective implementation of amplified bidirectional passive optical networks (PONs). First, we measured the maximum gains of two simple bidirectional optical amplifiers implemented without using any optical components for the suppression of reflected signals. From the results, the maximum gains of two simple bidirectional amplifiers with a broadband light source (BLS) seeded optical source were limited to be 27 dB due to the reflection-induced in-band crosstalk, when the reflectance coefficients were measured to be -33 dB in both directions. Then, we have also implemented a bidirectional optical amplifier with two band splitters for the amplified bidirectional PON where the two different wavelength bands were allocated to the downstream and upstream signals transmission. In our measurement, we confirmed that the maximum gain of bidirectional optical amplifier with two band splitters could be increased to more than 30 dB owing to the efficient suppression of in-band crosstalk.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.995-997
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• 2005

A plastic substrate for flexible display is developed. The gas barrier and optical properties of the substrate is improved through depositing silicon oxide/nitride layer and coating polymer layer on plastic film by sputtering process and wet coating process. Roll to roll processes will guarantee the productivity in the whole production process of the plastic substrate.

• Journal of the Korean Vacuum Society
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• v.16 no.6
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• pp.424-432
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• 2007

Luminance properties of external electrode fluorescent lamps and optical components in backlight unit (BLU) and optical transmission rates of optical sheets, are investigated for LCD-TV of 32" in diagonal with WXGA level resolution (1366$\times$768). The luminance is measured in 12-lamps and 18-lamps of BLU. The luminance uniformity preserves about 85 % in the 12-lamps backlight, while the luminance of optical components and the efficiency of backlight in the 12-lamps are lower than those in the 18-lamps backlight. When the lamp luminance in BLU having 12-lamps and 18-lamps is normalized as 100 %, the relative luminance of a diffusion plate, a diffusion sheet, a prism sheet (BEF), a polarization sheet (DBEF), has a constant value without dependence on a lamp luminance. The relative luminance of optical components in 12-lamps BLU is lower than that in 18-lamps backlight. The light transmission rate, the relative luminance of liquid crystal display panel with the luminance 100 % of backlight, is 7.14 % in the use of DBEF and BEF, 6.12 % in the use of only DBEF, and 3.21 % in the use of only BEF. Those Data obtained in this experiment for the lamps and optical components, are the design parameters for the LCD backlight.

• Korean Journal of Materials Research
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• v.18 no.8
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• pp.422-426
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• 2008

The effects of an addition of $ZrO_2$ on the microstructure and electrical properties of MgO films as a protective layer for AC plasma display panels were investigated. MgO + a 200 ppm $ZrO_2$ protective layer prepared by e-beam evaporation exhibited a secondary electron emission coefficient ($\gamma$) that was improved by 21% compared to that of a pure MgO protective layer. The relative density and Vickers hardness increased with a further addition of $ZrO_2$. These results suggest that the discharge properties and optical properties of MgO protective layers are closely related to the relative density and Vickers hardness. The good optical and electrical properties of $\gamma$, at 0.080, a grain size of $19\;{\mu}m$ and an optical transmittance of 91.93 % were obtained for the MgO + 200 ppm $ZrO_2$ protective layer sintered at $1700^{\circ}C$ for 5 hrs.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.9
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• pp.1094-1102
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• 2011

Recent trends for the miniaturization and weight reduction of portable electronic parts is the use of subminiature components. Assembly of the miniaturized components requires subminiature screws of which pitch sizes are in a micrometer scale. To produce such a subminiature screw with high precision threads, not only a precision forming technology but also high-precision measurement technique is required. In the present work, a vision inspection system is developed to measure the thread profile of a subminiature screw. Optical simulation based on a ray tracing method is used to design and analyze the optical system of the vision inspection apparatus. Through this simulation, optical performance of the developed vision inspection system is optimized. The image processing algorithm for the precision screw inspection is also discussed.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.6
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• pp.8-14
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• 2006

The object transport system is used in many industry field such as the conveyor belt, which transports huge goods in container harbor, the magnetic levitation system, and the indexing system which transports precision components such as semiconductor and optical components. In conventional transport system, the magnetic field may damage semiconductor and the contact force may scratch on the optical lens. So ultrasonic wave transport system has been proposed to replace the previous transport system. In this paper, the good transport condition of optical lens is obtained according to the flexural beam shapes. The working frequency and transport speed are measured and the vibration characteristics of the flexural beams are investigated by Laser Scanning Vibrometer.

• Journal of Electrical Engineering and information Science
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• v.3 no.3
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• pp.336-341
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• 1998

We describe the architecture of an optical cross-connect (OXC) which is modular in structure and is able to be upgraded to a virtual wavelength path by adding wavelength converters. The additional feature of the OXC is the all-optical nature. It can be implemented with commercial components including mechanical optical switches. As a result of the test on the experimental OXC, it has been shown that 2.5 Gb/s signal can be transmitted via the OXC through 100 km length o an ordinary single mode fiber with 3 dB penalty.