• Korean Journal of Optics and Photonics
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• v.17 no.5
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• pp.455-460
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• 2006

The output characteristics of a ceramic Nd:YAC laser pumped by a fiber-coupled laser diode was investigated. An efficiency and a slope efficiency of 33.8 % and 39.3 % respectively were obtained, under an output coupler reflectance of 90.4 %. The laser power has decreased suddenly due to the thermal tensing effect more than 6 W pumping powers.

• Laser Solutions
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• v.6 no.2
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• pp.19-26
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• 2003

6061 aluminum alloy sheets were I-square butt welded using a continuous wave Nd:YAC laser. Heat inputs were varied from 54.6 to 80 J/mm for butt welding using different sets of the laser power and the weld speed. I-square butt welds were also made with and without Ar shielding gas. The effect of Ar shielding gas and heat input on the mechanical properties and formability was investigated using Vickers hardness, transverse-weld tensile and bulge test. Porosity on the weld beads and sections and hot crack on the fracture surfaces of transverse-weld tensile test specimens were investigated using optical and scanning electron microscopy The experimental results showed that mechanical properties and formability of 6061 aluminum alloy laser welds were degraded compared to those of base metal. Mechanical properties and formability of 6061 aluminum alloy laser welds were not substantially changed when Ar shielding gas was supplied or heat inputs were varied.

• International Journal of Korean Welding Society
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• v.2 no.1
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• pp.15-20
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• 2002

This paper describes the weldability and mechanical behavior of JIS S45C medium carbon steel (corresponding to KS SM45C and SAE 1045) for machine structures in CW Nd:YAG laser welding. In general, medium carbon steels have a limited application to the industrial fields in spite of good mechanical characteristics. This is due to welding difficulty because of the high carbon contents and impurities in this material. Therefore, in this study the laser weldability of medium carbon steel with adjusted contents of S and P has been investigated in order to extend the application to medium carbon steels. Several experiments and numerical simulations have been conducted to determine the characteristics of mechanical behavior in CW Nd:YAC laser welds. The results of the simulations concur with the experiment results. From the result of this study, the application possibility of CW Nd:YAG laser welding to medium carbon steel has been confirmed. Also, the appropriateness of mechanical behavior simulation has been verified to analyze and predict the welding phenomena.

• Proceedings of the Korean Nuclear Society Conference
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• 2001.05a
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• pp.313.2-313
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• 2001

• Proceedings of the KWS Conference
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• 2003.05a
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• pp.90-92
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• 2003

• Proceedings of the Optical Society of Korea Conference
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• 2005.07a
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• pp.228-229
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• 2005

• Laser Solutions
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• v.7 no.2
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• pp.1-10
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• 2004

This work was attempted to join SCP sheet and STS304 sheet by using Nd:YAC laser beam. SCP sheet has good formability and low cost, while STS304 has excellent corrosion resistance and mechanical properties in high temp. In this experiment, butt joint type was used to develop the tailored blank welding for dissimilar steel. Sheets which have different thermal properties. Computer simulation was conducted to obtain the off-set position for efficient welding by considering laser power, scanning speed, focal length and basic properties. The result showed that the optimum thermal distribution was obtained when the laser beam was irradiated at $0.05{\sim}0.1$ mm off-set toward the SCP sheet side. The experiment was conducted based on the result of computer simulation to show the same optimum conditions. Optimum conditions were 3KW in laser beam power, 6m/min in scanning speed, -0.5mm in focal position, 0.1mm off-set toward SCP. Microhardness test, tensile test, bulge test, optical microscopy, EDS, and XRD were performed to observe the microstructure around fusion zone and to evaluate the mechanical properties of optimum conditions, The weld zone had high microhardness values by the formation of the martensitic structure. Tensile test measured the strength of welded region by vertical to strain direction and the elongation of welded region by parallel to strain direction. Bulge test showed $52\%$ formability of the original materials. Bead shape, grain size, and martensitic structure were observed by the optical microscopy in the weld zone. Detailed results of EDS, XRD confirmed that the welded region was connected of martensitic structure.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.7 s.172
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• pp.19-26
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• 2005

The objective of this study is to investigate the influence of process parameters, such as power of laser, cutting speed of laser and material thickness, on the practical cutting region and the kerfwidth fer the case of cutting of CSP IN sheet using high power Nd:YAC laser in continuous wave(CW) mode. In order to obtain the practical cutting region and the relationship between process parameters on the kerfwidth, several laser cutting experiments are carried out. The effective heat input is introduced to consider the influence of power and cutting speed of laser on the kerfwidth together. From the results of experiments, the allowable cutting region and the relationship between the effective heat input and kerfwidth fur the case of cutting of CSP 1N sheet using high power CW Nd:YAG laser have been obtained to improve the dimensionalaccuracyofthecutarea.

• Laser Solutions
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• v.11 no.3
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• pp.1-4
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• 2008

A selective laser micro bonding process using liquid glass (methylsilsesquioxane) was developed and the results are analysed. The liquid glass can be solidified with Nd:YAG laser irradiation and it can be applied for joining two glass substrates. A bonding thickness of a few micrometers can be achieved. The appropriate laser power density (or this process is around 40-60 $kW/cm^2$ and its bonding force is 1000-1200 $gf/mm^2$. This process can be applied for bonding micro devices such as micro bio-sensors or display products. Its advantages and limitations are presented and discussed.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05b
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• pp.330-334
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• 2004

본 논문에서는 Nd:YAC 레이저의 제 2고조파에 의해 펌핑되는 고체레이저의 다중통과 증폭기의 이론적 고찰에 대하여 논하였다. 다중통과 증폭기의 입력레이저는 Ti:sapphire 레이저이며, 펌핑광원의 주입 후 입력 빔의 통과 회수에 따른 추출효율, 소신호 이득계수에 대한 변화 등을 조사하여 다중통과 증폭을 위한 최적조건을 구하였다. 또한, 실험에서 2단 다중통과 증폭기에서 790 nm의 입력 파장을 주입하였을 때, 42 mJ의 최대 출력에너지, 21 ㏈의 증폭이득, 25%의 출력효율을 얻었다.