• 한국분말재료학회지
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• 제15권1호
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• pp.46-52
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• 2008

The restrictor, which is a fluid channel from a reservoir to a chamber inside a thermal micro actuator, has been fabricated using ArF and KrF excimer lasers, Diode-Pumped Solid State Lasers (DPSSL) and femtosecond lasers for a feasibility study. A numerical model of fluid dynamics for the actuator chamber and restrictor is presented. The model includes bubble formation and growth, droplet ejection through nozzle, and dynamics of fluid refill through the restrictor from a reservoir. Since an optimized and well-fabricated restrictor is important for a high frequency actuator, some special beam delivery setups and post processing techniques have been researched and developed. The effects of variations of the restrictor length, diameter, and tapered shapes are simulated and the results are analyzed to determine the optimal design. The numerical results of droplet velocity and volume are compared with the experimental results of a cylindrical-shaped actuator. It is found that the micro actuators having tapered restrictors show better high frequency characteristics than those having a cylindrical shape without any notable decrease of droplet volume. The laser-fabricated restrictors demonstrate initial feasibility for the laser direct ablation technique although more development is required.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 1999년도 High Temperature Superconductivity Vol.IX
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• pp.43-47
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• 1999

Instead of using KrF excimer lasers( ${\lambda}$ = 248 nm) in depositing oxide thin films, as in the most of the laboratories in Korea, we have used an ArF excimer laser( ${\lambda}$ = 197 nm) which has a shorter wavelength. By using a beam which has a shorter wavelength, we could obtain higher quality and smoother surface YBCO thin films. We fabricated YBCO thin films with the various substrate temperature conditions and analyzed the characteristics of these films. We also studied the charateristics of the films fabricated under the various conditions of the power of laser and the oxygen pressure. The characterization tools used in this work were a transport measurement setup, an XRD , and a SEM. We also fabricated STO/YBCO multilayers to use in SFQ devices fabrication. XRD patterns of the multilayers showed that the multilayer films were grown epitaxially.

• 한국정밀공학회지
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• 제22권7호
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• pp.79-87
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• 2005

This paper summarizes the work on the development of a simulation program for modelling the process of machining quasi-three dimensional shape with the excimer laser beam on a constantly moving polymers. Relatively simple masks of rectangle, triangle and half circle shape are considered. The etching depth is calculated by considering the number of laser pulses irradiated on the specimen surface. It was found that similar shapes as experimental results can be obtained by choosing suitable parameters of moving velocity, moving distance and mask sizes.

• 한국레이저가공학회지
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• 제15권2호
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• pp.1-5
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• 2012

Gelatin is used as a model for soft biological tissues in studying laser interaction with the soft tissues. In this work, we analyze the interaction between gelatin and excimer and Ti:Sapphire femtosecond laser under various conditions, especially by varying the laser, laser fluence and pulse number. The results show that swelling of the surface and ablation depth can be controlled by adjusting the process parameters.

• 마이크로전자및패키징학회지
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• 제21권2호
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• pp.53-57
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• 2014

Thin glass (< 100 microns) is a promising material from which advanced interposers for high density electrical interconnects for 2.5D chip packaging can be produced. But thin glass is extremely brittle, so mechanical micromachining to create through glass vias (TGVs) is particularly challenging. In this article we show how laser processing using deep UV excimer lasers at a wavelength of 193 nm provides a viable solution capable of drilling dense patterns of TGVs with high hole counts. Based on mask illumination, this method supports parallel drilling of up over 1,000 through vias in 30 to $100{\mu}m$ thin glass sheets. (We also briefly discuss that ultrafast lasers are an excellent alternative for laser drilling of TGVs at lower pattern densities.) We present data showing that this process can deliver the requisite hole quality and can readily achieve future-proof TGV diameters as small $10{\mu}m$ together with a corresponding reduction in pitch size.

• 한국레이저가공학회지
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• 제6권1호
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• pp.9-16
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• 2003

Micromachining using the DPSS 3rd Harmonic Laser (355nm) has outstanding advantages as a UV source in comparison with Excimer lasers in various aspects such as maintenance cost, maskless machining, high repetition rate and so on. It also has the greater absorptivity of many materials in contrast to other IR sources. In this paper, the process for micro-drilling of blind hole in Cu/PI/Cu substrate with the DPSS UV laser and the scanning device is investigated by the experimental methods. It is known that there is a large gap between the ablation threshold of copper and that of PI. We use the Archimedes spiral path for the blind hole with different energy densities to ablate the different material. Finally, the blind via hole of diameter 100$\mu\textrm{m}$ and 50$\mu\textrm{m}$ was drilled.

• 한국광학회:학술대회논문집
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• 한국광학회 1991년도 제6회 파동 및 레이저 학술발표회 Prodeedings of 6th Conference on Waves and Lasers
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• pp.1-1
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• 1991

The fabrication of computer components requires a great variety of optical equipment. The patterning of integrated circuits is performed either on step-and-repeat cameras, scanning systems or step-and-repeat systems. The image forming optics used in these machines is quite difficult to design and fabricate. In addtion several layers of patterns must be precisely superposed, and also the illuminators have to provide the final irradiance in the image plane constant to within 1%. Other uses of specialized optical equipment are mass production of chip packages, inspection scanners and laser ablation cameras for polymers. The details of some of these systems will be described with particular ephasis on different optical structures and the use of excimer lasers as light sources.

• Journal of Yeungnam Medical Science
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• 제40권4호
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• pp.423-425
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• 2023

Porokeratosis ptychotropica is an uncommon form of porokeratosis, which was initially described in 1995. It is clinically characterized by symmetrical reddish to brown-colored hyperkeratotic, verrucous, or psoriasiform plaques on the perianal and gluteal regions. The lesions tend to integrate and expand centrally, with small peripheral satellite lesions. Early skin biopsy and appropriate diagnosis are essential because malignant change occurs in 7.5% of porokeratotic lesions. Conventional treatment options include topical steroid, retinoid, imiquimod, 5-fluorouracil, isotretinoin, excimer laser, photodynamic therapy, intralesional steroid or bleomycin injection, cryotherapy, carbon dioxide (CO₂) laser, and dermatome and excision, but none seem to achieve complete clearance. A 68-year-old woman presented with diffuse hyperkeratotic scaly lichenoid plaques on the buttocks that had persisted for several years. A skin biopsy of the buttocks revealed multiple cornoid lamellae and intense hyperkeratosis. There were some dyskeratotic cells beneath the cornoid lamellae and the granular layer was absent. Porokeratosis ptychotropica was diagnosed based on the characteristic clinical appearance and typical histopathological manifestations. She was treated with a CO₂ laser in one session and topical application of urea and imiquimod cream for 1 month. The lesions slightly improved at the 1-month follow-up. We herein present a rare case of porokeratosis ptychotropica.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.561-569
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• 2002

Laser has been called a "Quantum Machine" because of its mechanism of generation since the development on July 7,1960.by T.H.Maiman. We can now use this machine as a tool for manufacturing in industries. At present, 45kW CO2 laser, 10kW Nd:YAG laser, 6kW LD pumped YAG laser and 4kW direct diode laser facilities are available for welding a heavy steel plate of 40mm in thickness and for cutting metals at high speed of 140m/min. Laser Materials Processing is no longer a scientific curiosity but a modern tool in industries. Lasers in manufacturing sector are currently used in welding, cutting, drilling, cladding, marking, cleaning, micro-machining and forming. Recently, high power laser diode, 10kW LD pumped YAG laser, 700W fiber laser and excimer laser have been developed in the industrialized countries. As a result of large numbers of research and developments, the modem laser materials processing has been realized and used in all kinds of industries now. In the present paper, metallurgical studies on laser materials processing such as porosity formation, hot cracking and the joint performances of steels and aluminum alloys and dissimilar joint are discussed after the introduction of laser facilities and laser applications in industries such as automotive industry, electronics industry, and steel making industry. The wave towards the use of laser materials processing and its penetration into many industries has started in many countries now. Especially, development of high power/quality diode laser will be accelerate the introduction of this magnificent tool, because of the high efficiency of about 50%, long life time and compact.

• 한국자기학회지
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• 제15권1호
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• pp.21-24
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• 2005

강자성, 초거대자기저항체인 $La_{0.67}Sr_{0.33}MnO_{3}$ 타겟을 이용하여 248nm의 파장을 갖는 KrF 엑시머 레이저를 사용한 PLD법으로 박막으 제작하고, 강유전체 물질인 $PbZr_{0.52}Ti_{0.48}O_{3}$ 물질을 spin coating 방법으로 제조하였다. Pt 기관(111)위에 125 mtorr의 산소분압으로 증착한 rhombohedral 구조를 갖는 LSMO 박막을 증착하고 그 위에 PZT 물질을 증착한 결과 LSMO, PZT en 물질 모두 단일상으로 [111]방향으로서의 성장하였음을 알 수 있었다. AFM(atomic force micrscope) data 및 SEM(scanning electron microscope) data를 바탕으로 매우 균질한 박막을 얻었음을 알 수 있었으며, 이때의 자기적 성질 및 전기적 성질은 각각 강자성적인 성질 및 강유전체적인 성향을 나타내었다. 이러한 결과를 가지고 박막증착에 있어서 서로간의 결정구조가 미치는 영향과 다른 경향에 대한 조절이 가능함을 알 수 있었다.