• Proceedings of the Korean Society of Laser Processing Conference
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• 1998.11a
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• pp.20-23
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• 1998

• Korean Journal of Optics and Photonics
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• v.1 no.2
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• pp.204-209
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• 1990

The temperature variation at a laser rod center induced by high repetetion rate pumping was measured by counting the number of inteference frigne shift and found to be consistent with the theoretical value obtained from heat diffusion equation. The spatial homogeneity and energy transfer rate of flashlamp pumping by the single elliptical reflector plated with gold were evaluated by measuring interference fringes oever the cross section of a Nd:YAG laser rod.

• Korean Journal of Optics and Photonics
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• v.9 no.3
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• pp.186-190
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• 1998

We fabricated a diode-side pumped high power Nd:YAG laser with a gold coated flow tube(diameter of 10mm) and three sets of 140W diode bar. The diameter of Nd:YAG rod was 6mm and its length was 130mm. We obtained 130W cw power from a linear resonator with an 11% output coupler, which corresponds to the slope efficiency of 43% and the optical efficiency of 31%. The measured beam quality factor(M$^2$) reached about 85 which is fairly large due to the large size of the rod. Thermal lensing of the rod was measured to be 5.3-7.4D/$kW_{pump}$ when the laser was operating.

• Korean Journal of Optics and Photonics
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• v.14 no.1
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• pp.44-50
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• 2003

This paper describes the thermal effect at Nd:YAG using a laser-diode side-pumping. To detect the depolarization loss and the retardation caused by the thermal effect, a λ/4 plate is inserted between the polarizer and the Nd:YAG laser material. Using a CCD has allowed detection of the variation of the beam pattern that could analyze the change of the refractive index of the Nd:YAG laser material by the thermal effect. Through the change of the probe beam power, we know that 21% of the pumping power was converted into heat in the material. The depolarization loss was 24.7% under a temperature of $25^{\circ}C$ of the laser material and a pumping power of 15 W. The inhomogeneous distribution showed that the retardation angle was 7$^{\circ}$ in the center of the material and 19$^{\circ}$ on the edge of it. It is confirmed that the thermal effect is analyzed at the each point of the laser material and it suggests an effective method to reduce the thermal effect on the LD side-pumped laser material.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.1
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• pp.137-146
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• 2008

Nd:YAG pulse laser welding of stainless steel plate was simulated to find welding condition by using commercial finite element code MARC. Due to geometric symmetry, a half model of AISI 304 stainless steel plate was considered and user subroutines were applied to boundary condition for the heat transfer. Material properties such as conductivity, specific heat, mass density and latent heat were given as a function of temperature. As results, Three dimensional heat source model for pulse laser beam conditions of butt welding has been designed by the comparison between the finite element analysis results and experimental data on AISI 304 stainless steel plate. Nd:YAG laser welding for AISI 304 stainless steel was successfully simulated and it should be useful to determine optimal welding condition.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1302-1308
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• 2003

Welding characteristics of austienite 304 stainless steel and SM45C using a continuous wave Nd:YAG laser are experimentally investigated. Laser beam welding is increasingly being used in welding of structural steels. The laser welding process is one of the most advanced manufacturing technologies owing to its high speed and deep penetration. This paper describes the weld ability of SM45C carbon steel and austienite 304 stainless steel for machine structural use by Nd:YAG laser.

• Proceedings of the Korean Society of Laser Processing Conference
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• 2003.05a
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• pp.35-38
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• 2003

• Journal of Oral Medicine and Pain
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• v.20 no.2
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• pp.283-289
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• 1995

레이저가 의학영역에서 사용된 후 구강내 연조직과 경조직 병소에 대한 임상적 적용에 관한 관심이 커져왔다. 레이저가 조사되는 부위에서는 대부분 연기가 발생한다. 이 경우 병원체가 존재하는 병소에 대한 레이저치료시 발생되는 연기속에 병원체가 포함되어 이Tekas 환자와 술자는 이의 흡입가능성이 크므로 균혈증 및 상기도나 호흡계의 의원성 감염이 유발될 수 있다. 저자는 레이저치료시 발생되는 연기속에 병원체가 포함되어 있는지의 여부를 규명하기위해 각각 10개의 실험군에 통기성 미생물인 Escherichia coli(E.coli)가 배양된 brain geart infusion (BHI) 배지와 E.coli 가 존재하는 치근단 병소를 실험적으로 만든 후 각각 pulsed Nd:YAG 레이저를 조사해 연기를 채취, 배양, 분석하여 다음과 같은 결과를 얻었다. 1. Pulsed Nd:YAG 레이저를 E. colir 배양된 agar substrate 와 실험적으로 만들어진 치근단부위의 E.coli 현탁액에 조사시 발생된 연기에서 처음 접종된 것과 같은 E.coli가 검출되었다. 2. 감염병소에 pulsed Nd:YAG 레이저를 조사시 발생되는 연기의 유해효과로부터 환자와 술자 및 보조자의 보호를 위해 효과적인 흡입기를 사용이 권장된다.

• Korean Journal of Optics and Photonics
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• v.18 no.3
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• pp.208-215
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• 2007

A fiber-coupled laser-diode pumped ceramic Nd:YAG laser for compensating the thermal tensing effect was developed. The thermal tensing effect was compensated using a convex lens, which was 25 mm away from the laser rod, with a focal length of 30 mm and an effective clear aperture of 22 mm. Without a compensator, the laser output power decreased suddenly above a pump power of 6 W. Using a compensator, the laser output power increased linearly according to the pump power. The beam propagation factor $M^{2}$ was 2.4 under a pump power of 12 W.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.176-177
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• 2005

PDMS는 생명공학 분야에서 중요한 기술적 폴리머이다. Nd:YAG레이저의 4고조파 ($\lambda$=266nm, pulse) 레이저를 사용하여 표면 처리를 하여 PDMS 표면의 습윤성과 접착성의 향상됨을 확인하였다. 식각한 PDMS는 샘물체의 미세회로에 사용될 수 있다. 본 논문은 레이저 빔의 주사속도를 변화시키며 PDMS를 레이저로 식각하며 PDMS의 식각 특성을 연구한다 식각 특성을 의존성이 가장 효과적인 주사 속도에 대한 의존성을 규명하고자 스테이지 컨트롤러의 속도를 변화시키며 실험하였다. 그리고 최적의 레이저 출력값을 알아내려고 레이저 출력값을 조절하며 실험 하였다. 단차측정기(알파스템)을 이용하여 식각형상과 식각 효율 등을 분석하였다.