• 한국레이저가공학회:학술대회논문집
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• 한국레이저가공학회 2006년도 추계학술발표대회 논문집
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• pp.41-45
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• 2006

Auto focusing system to find optimized focal position of laser beam used for material process has been investigated by using fiber confocal method. Wavelength of laser diode (LD) and diameter of single-mode fiber we 780nm and $5.3{\mu}m$, respectively. Intensity distributions of beam reflected from the surface of mirror and silicon bare wafer have been observed in a gaussian form. Experimental results show that focal position obtained by LD is shifted from one observed from surface scribed by laser about $80{\mu}m$. It is due to the difference of wavelength and each divergence of between LD and laser used for material process. It is confirmed that auto focusing control system through position calibration has operated steadily.

• Transactions on Electrical and Electronic Materials
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• 제14권2호
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• pp.59-62
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• 2013

At an infra-red (IR) wavelength of 1,064 nm, a diode-pumped Q-switched $Nd:YVO_4$ laser was used for the direct patterning of various transparent conductive oxide (TCO) thin films on glass substrate. With various laser beam conditions, the laser ablation results showed that the indium tin oxide (ITO) film was removed completely. In contrast, zinc oxide (ZnO) film was not etched for any laser beam conditions and indium gallium zinc oxide (IGZO) was only ablated with a low scanning speed. The difference in laser ablation is thought to be due to the crystal structures and the coefficient of thermal expansion (CTE) of ITO, IGZO, and ZnO. The width of the laser-patterned grooves was dependent on the film materials, the repetition rate, and the scanning speed of the laser beam.

• 한국레이저가공학회지
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• 제8권2호
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• pp.21-32
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• 2005

The excimer laser ablation of a polymer occurs by the excitation of chemical bonds to energy levels that are above the dissociation energy. In this process, however, fragmented debris is finally ejected explosively by the scission of bonds and accumulates on the material surface. In the present work, a process for eliminating surface debris contamination generated by the laser ablation of a polymer is developed. The proposed approach for removing surface debris utilizes an erasable ink pasted on a polymide. The ink pasted polyimide is ablated by KrF excimer laser. The surface debris ejected from the polyimide is then combined with the ink layer on the polymer. Finally, both the surface debris and the ink layer are removed using adhesive tape or alcohol solvent. The results suggest that the erasable ink method is a simple, low cost, and extremely effective debris eliminating process.

• 센서학회지
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• 제22권1호
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• pp.49-53
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• 2013

In this paper, we proposed a laser-based non-contact temperature measuring method for high speed rotating polycarbonate (PC) disk using transparency change of thermocolor. The thermocolor has abilities to change color and transparency due to a change in temperature. The thermocolor is applied on one side of polyvinylidene fluoride (PVDF) membrane. The thermocolor applied membrane is attached to inside of reaction chamber in disk. An optical system consisted of a laser beam radiator and a laser photometer is installed. Laser is irradiated at the bottom side of disk and the transmitted laser beam is detected by the laser photometer at the opposite side of disk. During the disk is rotating, laser is irradiated and detected simultaneously. The laser photometer senses the transmitted laser power and generates voltage as output. The temperature of disk can be detected during the disk is rotating up to 3000 RPM.

• 한국레이저가공학회지
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• 제6권2호
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• pp.27-33
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• 2003

A laser shock cleaning technology is a new dry cleaning methodology for the effective removal of small particles from the surface. This technique uses a plasma shock wave produced by a breakdown of air due to an intense laser pulse. In order to optimize the laser shock cleaning process, it needs to evaluate the cleaning performance quantitatively by using a monitoring technique. In this paper, an acoustic monitoring technique was attempted to investigate the laser shock cleaning process with an aim to optimize the cleaning process. A wide-band microphone with high sensitivity was utilized to detect acoustic signals during the cleaning process. It was found that the intensity of the shock wave was strongly dependent on the power density of laser beam and the gas species at the laser beam focus. As a power density was larger, the shock wave became stronger. It was also seen that the shock wave became stronger in the case of Ar gas compared with air and N$_2$ gas.

• Design & Manufacturing
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• 제15권3호
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• pp.26-31
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• 2021

In this study, laser-induced periodic surface structure (LIPSS) was fabricated on Ni, Si, and GaAs samples using a flat-top beam with a uniform energy distribution that was fabricated using a Gaussian femtosecond laser with a mechanical slit and tube lens. Unlike the Gaussian beam, the flat-top beam has a uniform beam profile, therefore the center and the periphery of the fabricated LIPSS have similar line periodicity. In addition, LIPSS was obtained not only in metals but also in metalloids and metals and metalloid compounds by using the narrow pulse width characteristic of a femtosecond laser.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1984년도 하계학술회의논문집
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• pp.299-301
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• 1984

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2009년도 춘계학술대회 논문집
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• pp.761-762
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• 2009

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1998년도 추계학술대회 논문집
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• pp.66-71
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• 1998

• 한국통신학회논문지
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• 제19권1호
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• pp.100-110
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• 1994

본 연구에서는 효율적인 광원과 광도파로간의 결합방법으로서 많은 연구가 진행중인 monolithic laser-waveguide coupler 특성해석에 beam propagation method를 도입하여 기존의 방법과 비교검토 한 결과 타당성을 입증할 수 있었으며, 또한 결합효율을 향상시키기 위하여 taper 구조를 가진 monlithic laser-waveguide coupler를 제시하였다. monolithic laser-waveguide coupler는 능동소자인 laser의 특성과 수동소자인 waveguide의 특성을 동시에 가지고 있으므로 고려하여야할 요소가 매우 많고, 또 각 요소들의 변화에 따라 결합기의 성능이 크게 좌우되므로 그 특성 연구가 많은 어려움이 있었다. 때문에 본 연구에서는 방향성 결합기를 사용한 모델을 해석하는 방법으로 기존의 coupled mode 이론을 사용할 수도 있겠으나, 본 연구에서와 같이 많은 변수를 가지는 경우의 해석에는 적용하기 어렵다는 단점 때문에 beam propagation method를 사용한 해석을 시도하였다. 또한 해석에 있어서 가장 기본이 되는 초기전개의 계산에서도 종래의 연구에서와 달리 근사식을 이용해 전계를 계산하지 않고, 주어진 구조에 대하여 직접 finite difference method를 적용하여 초기전계를 구하였다. 이러한 새로운 시도들이 가지는 잇점을 방법과 비교하여 알아 보았으며, 새로운 방법의 적용을 통하여 보다 많은 변수를 고려하여 monolithic laser-waveguide coupler의 특성을 연구할 수 있었다. 이러한 과정을 통하여 결합기의 특성을 파악하고 그 결과로 monolothic laser-waveguide coupler의 특성중 가장 중요한 결합특성을 향상 시키기 위해서 taper영역을 가지는 monolothic laser-waveguide coupler를 제안하였다. 본 연구에서 제안한 구조에 대하여 특성을 조사해본 결과 79%정도의 좋은 결합효율을 얻을 수 있었다.