• Journal of the Korean Ceramic Society
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• v.54 no.3
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• pp.167-183
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• 2017

Zinc oxide (ZnO) is one of the most versatile semiconductors, and one-dimensional (1D) ZnO nanostructures have attracted significant interest for use in ultraviolet (UV) lasers, photochemical sensors, and photocatalysts, among other applications. It is known that 1D ZnO nanowires can be fabricated readily owing to the anisotropic growth of ZnO along the [0001] direction. However, this type of growth results in a decrease in the surface area of the (0001) plane, which plays a vital role not only in UV lasing but also in the photocatalytic process. Thus, we attempted to synthesize ZnO crystals with an increased polar surface area by controlling the crystal growth process. The purpose of this review is to propose a simple route for the synthesis of plate-like ZnO crystals with highly enhanced polar surfaces and to explore their feasibility for use in UV lasers as well as as a photocatalyst and antibacterial agent. In addition, we highlight the recent progress made in the pilot-scale synthesis of plate-like ZnO crystals for industrial applications.

• Korean Journal of Optics and Photonics
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• v.32 no.5
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• pp.209-214
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• 2021

High-power continuous-wave operation of a Yb-doped double-clad fiber laser at 1018 nm, pumped by high-power diode lasers at 976 nm, is reported. Based on numerical calculation of the gain and laser signal power along the length of the Yb fiber, it is found that robust operation at 1018 nm can be achieved for a high Yb³⁺-ion excitation density greater than 11.5%, accompanied by high suppression of the feedback from the fiber's end facet. The Yb fiber laser constructed in house yields 626 W of continuous-wave output at 1018 nm for 729 W of incident pump power, corresponding to a slope efficiency of 86.6%. The prospect for power scaling is considered.

• Korean Journal of Optics and Photonics
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• v.27 no.3
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• pp.95-100
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• 2016

High-power quasi-continuous-wave (qcw) operation in Yb-doped double-clad fiber lasers with near-diffraction-limited quality of the output beam is reported. Based on numerical simulation, we built a simple, all-fiberized Yb fiber laser, and a fiber-based master-oscillator power amplifier (MOPA). Both laser systems have successfully produced qcw output with average power greater than 150 W at 1080 nm and 10 ms pulse duration at 10 Hz repetition rate, corresponding to a peak power greater than 1.5 kW for 205 W of pump power at 976 nm. Laser performance, including beam quality and slope efficiency, was characterized in both configurations. Prospects for power scaling and applications are discussed.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2009.01a
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• pp.566-571
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• 2009

A calibration method for multiple sets of stereo vision cameras is proposed. To measure the three-dimensional shape of a very long object, measuring the object at different viewpoints and registration of the data are necessary. In this study, two lasers beams generate two strings of calibration targets, which form straight lines in the world coordinate system. An evaluation function is defined to calculate the sum of the squares of the distances between each transformed target and the fitted line representing the laser beam to each target, and the distances between points appearing in the data sets of two adjacent viewpoints. The calculation process for the approximation method based on data linearity is presented. The experimental results show the effectiveness of the method.

• Design & Manufacturing
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• v.15 no.4
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• pp.65-71
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• 2021

In the early days of laser invention, it was simply used as a measuring tool, but as lasers became more common, they became an indispensable processing tool in the industry. Short-wavelength lasers are used to make patterns on wafers used in semiconductors depending on the wavelength, such as CO2 laser, YAG laser, green laser, and UV laser. At first, the hole of the PCB board mainly used for electronic parts was not thin and the hole size was large, so a mechanical drill was used. However, in order to realize product miniaturization and high integration, small hole processing lasers have become essential, and pattern exposure for small hole sizes has become essential. This paper intends to analyze the characteristics through patterns by exposing the PCB substrate through DMD and polygon scanner, which are different optical systems. Since the optical systems are different, the size of the patterns was made the same, and exposure was performed under the optimal conditions for each system. Pattern characteristics were analyzed through a 3D profiler. As a result of the analysis, there was no significant difference in line width between the two systems. However, it was confirmed that dmd had better pattern precision and polygon scanner had better productivity.

• Proceedings of the Optical Society of Korea Conference
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• 2003.07a
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• pp.2-3
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• 2003

오늘날 레이저는 수많은 종류가 등장하였으며 출력개선은 물론 장치의 규모도 나날이 Compact하게 발전하였다. 또한 그 활용성도 대단히 증가하여 의료, 과학, 군사분야를 시작으로 1990년에 이르면서 산업 전 분야에 파급되어 원자력, 전기／전자, 자동차, 반도체 등 주요산업의 제품수준을 향상시키는 핵심기술로 이용되고 있다. 레이저는 이와 같이 새로운 생산도구로서 위치를 확립 시키면서 산업분야의 다양성과 함께 가공산업에서 요구되는 레이저 관련 기술도 다양하게 진보하고 있는 추세이다. (중략)

• Journal of the Korean Vacuum Society
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• v.15 no.5
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• pp.435-450
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• 2006

Free electron lasers (FELs) are promising sources of coherent radiation that can provide users with radiations having a wide-range frequency-tunability and good spectral characteristics for basic science and industrial applications. Especially in Terahertz or X-ray ranges of spectrum, FELs can generate much stronger radiations than conventional light sources. In this paper, we introduce the working principles and key technologies of FELs, the status and the prospects of FEL developments.

• Tribology and Lubricants
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• v.35 no.5
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• pp.294-299
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• 2019

Most previous studies on water repellent surfaces using lasers rely on the use of pico- or femtosecond lasers. However, in industrial application, these methods have the disadvantages of high cost and low efficiency. In this study, we implement a hydrophobic surface using a high-power general-purpose diode laser. We have fabricated the microsurface using laser groove processing technology, and we present the correlation of wettability characteristics with space and width. The metal material is stainless steel (SUS 304), and the groove height during laser processing is set to $30{\mu}m$ to evaluate the wettability based on the gap and width of various grooves. Results show that the contact angle of the groove-shaped surface is increased by $40^{\circ}$ or more as compared with the surface without patterning, and the contact angle in the parallel direction is greater than that in the perpendicular direction. Results from contact angle hysteresis measurement experiments show that the groove width has a greater influence on the contact angle history than does the gap between grooves. In addition, the coating reveals that the contact angle can be increased using a chemical method and that the laser grooving process can further improve the wetting properties of the surface.

• Electronics and Telecommunications Trends
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• v.33 no.3
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• pp.59-69
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• 2018

Terahertz (THz) imaging and spectroscopy have been developed as non-destructive testing methods for various industrial applications. However, they have not been widely adopted in real applications owing to a high system price and the large size of conventional THz time-domain spectroscopy systems, which are based on ultrashort optical pulse lasers. Recently, various types of compact THz emitters and detectors have become available. As a result, THz non-destructive test (NDT) systems have become viable solutions. Herein, we briefly review the recent advances in THz NDT techniques adopting continuous-wave THz systems, including our recent results of a THz-based waterproof test system and an electrical connection inspection system for car manufacturing.

• Journal of Industrial Technology
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• v.16
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• pp.147-155
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• 1996

There is a considerable interest in tunable DFB-LD for their use in OFDM and coherent optical communications. In this paper, A modeling of ${\lambda}/4$-shifted tunable wavelength three electrode DFB-LD was performed considering the spatial hole burning within a laser diode cavity. The modeling will show design paramenters' requirement for high-speed and broad bandwidth lasers. The simulations of modeling prove that the continuous tuning range is about 3nm and the SMSR is about several dB. We showed that the optical power and carrier density distribution along z for several dc current with SHB. It was shown that prove that optical power and carrier density along cavity are changed and thismeans that modeling is correct.