• 한국자기학회:학술대회 개요집
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• 한국자기학회 1999년도 추계연구발표회 논문개요집
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• pp.68-69
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• 1999

• 한국레이저가공학회지
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• 제6권3호
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• pp.11-17
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• 2003

Recoil force exerted on the substrate during a nanosecond laser ablation of silicon is measured. The ablation sample is placed at the end of a 400 $\mu\textrm{m}$ thick and 13 mm long silicon cantilever. The vibration amplitude of the cantilever induced by the recoil force is measured in real time with a probe beam. By comparing the deflection amplitude of the cantilever with a theoretical model, the recoil momentum is estimated. For laser irradiance in the order of 10$\^$11/ W/$\textrm{cm}^2$, the recoil pressure reached a value over 40${\times}$10$\^$9/ Pa.

• 대한소아치과학회지
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• 제23권4호
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• pp.954-967
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• 1996

Laser application to modify healthy permanent dentin to improve microhardness and caries resistence has been previously reported but the physical modification and ablation thresholds of carious and sclerotic dentin has yet to be identified. This study determined the energy density required by modify (physical modification threshold, PMT) and remove (ablation threshold, AT) infected carious, affected and selerotic dentin compared to healthy permanent dentin. $1{\pm}0.25mm$ thick dentin sections(n=272) from extracted human teeth were used. Smear layer was removed 0.5M EDTA for 2 minutes. Utilizing three pulsed fiberopitc delivered contact lasers with different emission wavelengths($1.06{\mu}m$=Nd : YAG, $2.10{\mu}m$=Ho : YAG and $2.94{\mu}mEr$ : YAG). The energy density($J/cm^2$) was incrementally increased and the resulting tissue interaction classified on a scale from 0-6. A minimum of 5 repetitions/energy density were completed. Light microscopy(10-25X) was used to verify the physical modification(scale=3) and ablation thresholds(scale=4) of the various forms of dentin and the data were analyzed by logistic regression at the 95 % confidence interval. PMT and AT by the laser and the dentin types were: PMT and AT was lower in infected dentin than in sound dentin for all lasers. PMT and AT induced by Nd : YAG>Ho : YAG>Er : YAG for all forms of dentin. Microhardness was increased in sound dentin at PMT. Morphology of crater examined by light microscopy showed Nd : YAG was safe and effective for removing carious dentin and Er: YAG was effective for removing sound dentin. The PMT and AT for YAG lasers are different as a function of dentin type which may be utilized for selective modification and removal of dentin.

• 대한기계학회논문집B
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• 제27권9호
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• pp.1335-1341
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• 2003

This paper describes the process of nanoparticle synthesis by laser ablation of microparticles and consolidated sample. We have generated nanoparticles by high-power pulsed laser ablation of AI, Cu and Ag microparticles using a Q-switched Nd:YAG laser (wavelength 355nm, FWHM 6ns, fluence $0.8{\sim}2.0J/cm^2$). Microparticles of mean diameter $18{\sim}80{\mu}m$ are ablated in the ambient air. The generated nanoparticles are collected on a glass substrate and the size distribution and morphology are examined using a scanning electron microscope and a transmission electron microscope. The effect of laser fluence, collector position and compacting pressure on the distribution of particle size is investigated. To better understand the process of laser ablation of microparticle(LAM), we investigated the Nd: YAG laser-induced breakdown of Cu microparticle using time-resolved optical shadow images. Nanosecond time-resolved images of the ablation process are also obtained by laser flash shadowgraphy. Based on the experimental results, discussions are made on the dynamics of ablation plume.

• 한국레이저가공학회:학술대회논문집
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• 한국레이저가공학회 2006년도 춘계학술발표대회 논문집
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• pp.9-15
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• 2006

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 추계학술대회 논문집
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• pp.511-514
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• 2000

This work aimed to develop ITO (Indium Tin Oxide) thin films ablation with a KrF Eximer laser required for the application in flat panel display, especially patterning into small geometry on a large substrate area. The threshold fluence for ablating ITO on glass substrate is about 0.1 J/cm$^2$. And its value is much smaller than using third harmonic Nd:YAG laser. Through the optical microscope measurement the surface color of the damaged ITO is changed into dark brown and irradiated spot is completely isolated form the undamaged surroundings by laser light. The XPS analysis showed that the relative surface concentration of Sn and In were essentially unchanged (In :Sn=5:1) after irradiating Eximer laser. Using aluminium mask made by second harmonic Nd:YAG laser the ITO patterning is carried out.

• 방사성폐기물학회지
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• 제8권3호
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• pp.181-188
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• 2010

레이저 용발법에 의한 금속 표면 제염특성을 평가하였다. 레이저로는 파장 532 nm, 펄스에너지 150 mJ, 펄스폭 5 ns의 큐스위치 Nd:YAG를 적용하였고, 금속 표면에 $CsNO_3$, $Co(NH_4)_2(SO_4)_2$, $Eu_2O_3$ 그리고 $CeO_2$를 오염시켜 이들의 제염 특성을 평가하였다. 제염 변수로는 레이저 적용횟수, 레이저 에너지 밀도 및 레이저 조사 각도 특성을 평가하였으며 각각 8, 13.3 J/$cm^2$ 및 $30^{\circ}$의 최적 조건을 확인하였다. 제염 효율은 오염성분의 비점과 관련이 있었으며 $CsNO_3>Co(NH_4)_2(SO_4)_2>Eu_2O_3>CeO_2$ 순이었다. 또한 여러 에너지 밀도 조건에서 스테인레스 스틸 재질의 식각 깊이 제어 특성을 규명하였다.

• 반도체디스플레이기술학회지
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• 제8권4호
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• pp.31-36
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• 2009

In this paper, the laser cutting characteristics of the flexible PCB using high power Nd:YAG UV laser were investigated. A specific FPCB model was selected for the experiment. Test sheets were made, which had equal materials and layer structure to those of the outline (OL) region and the contact pad (CP) region in the FPCB. The experiment is made up of two stages. In the first stage of the experiment, the laser cutting fluence was found, which is the threshold fluence to cut the test sheets completely. The laser cutting fluence of the OL sheet is $1781.26{\sim}1970.16\;J/cm^2$ and that of the CP sheet is $2109.34{\sim}2134.34\;J/cm^2$. In the second stage, cutting performance and its qualities were analyzed by the experiment. The laser cutting performance remained almost unchanged for all laser and process parameter sets. The average cutting width (top side/bottom side) of the OL sheet was $40.45\;{\mu}m/11.52\;{\mu}m$ and that of the CP sheet was $22.14\;{\mu}m/10.93\;{\mu}m$. However, the laser cutting qualities were different according to the parameters. The adjacent region of the cutting line on the OL sheet was carbonized as the beam speed was low and the overlap coefficient was high. The surface quality around the cutting line of the CP sheet was about the same. Carbonization and debris occurred on the surface of the cutting line. As a result of the experiment, the cutting qualities were better as the overlap coefficient was made low and beam speed high. Therefore, the overlap coefficient 2 or 3 is proper for the FPCB laser cutting.

• 한국레이저가공학회지
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• 제5권2호
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• pp.31-38
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• 2002

This paper describes the process of nanoparticle synthesis by laser ablation of consolidated microparticles. We have generated nanoparticles by high-power pulsed laser ablation of Al, Cu and Ag microparticles using a Q-switched Nd:YAG laser (wavelength 355 nm, FWHM 5 ㎱, fluence 0.8∼2.0 J/㎠). Microparticles of mean diameter 18∼80 ㎛ are ablated in the ambient air The generated nanoparticles are collected on a glass substrate and the size distribution and morphology are examined using a scanning electron microscope and a transmission electron microscope. The effect of laser fluence and collector position on the distribution of particle size is investigated. The dynamics of ablation plume and shock wave is analyzed by monitoring the photoacoustic probe-beam deflection signal. Nanosecond time-resolved images of the ablation process are also obtained by laser flash shadowgraphy. Based on the experimental results, discussions are made on the dynamics of ablation plume.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2012년도 제38회 춘계학술대회논문집
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• pp.429-434
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• 2012

금속 연료로 사용되는 마이크로/나노 알루미늄 입자를 산화피막에 의한 점화 지연을 최소화 하는 점화 방법을 제시 하였다. 알루미늄 입자를 생성시킴과 동시에 가열하여 입자가 생성된 직후 산소와 접촉시 격렬한 산화 반응을 유도하여 점화를 시키는 방법이다. 1064 nm 파장의 Nd:YAG 펄스 레이저를 이용한 레이저 삭마(laser ablation)를 알루미늄 시편에 발생시켜 입자를 생성하였으며, 산란 기법(scattering method)을 이용하여 입자를 가시화하여 생성을 확인하였다. 10.6 ${\mu}m$ 파장의 $CO_2$ 연속 레이저를 사용하여 알루미늄 시편을 가열하고 생성된 입자의 점화 열원으로 사용하여 알루미늄 입자가 점화되고 연소되어 이동하는 궤적을 확인하였다.