• Proceedings of the Korea Association of Crystal Growth Conference
• /
• 1998.06a
• /
• pp.165-167
• /
• 1998

Nd:YAG crystals were grown by Horizontal Bridgman method. The effects of sliding rate (growth rate) of Molydbenum container, growth atmosphere and concentration of Neodymium ions on crystal qualities were investigated. The size of the crystals grown was up to 150-200 mm in length, 70 mm in width and 25-35 mm in thickness. Crystals grown under the optimum conditions were violet, transparent and could not be observed any macroscopic defects. Under the polarizing microscopoc observations with crossed polar, striations, {211} facets and inclusions were detected. With the grown crystals, prototypes of laser rods for 1.06$\mu$m laser application were manufactured and then characterized. As a result, we can get high quality of Nd:YAG laser rods with <111> and <110> axis, 63 mm in length and6.3 mm in diameter.

• Proceedings of the KIEE Conference
• /
• 1989.07a
• /
• pp.633-636
• /
• 1989

The simulation results of the third harmonic conversion with 1.064 um Nd :YAG laser using polarization mismatch method are reported. The third harmonic conversion efficiency was over 65% for the Gaussian incident pulse of $300{\sim}400MW/cm^2$ peak intensity, and over 80% for $3{\sim}4GW/cm^2$ peak intensity pulse. The dependence of the third harmonic conversion efficiency' on the variation of incident polarization angle ${\theta}_p$ and angular discrepancy ${\Delta}{\theta}$ of phase matched angle ${\theta}_m$ is discussed.

• Journal of the Korean Society for Precision Engineering
• /
• v.22 no.8 s.173
• /
• pp.17-26
• /
• 2005

Dissimilar-metal welds(DHWs) are used widely in various industrial applications due to the pratical importance from the technical and economic aspect. However, DMWs have several fabricative and metallurgical drawbacks that can often lead to in-service failures. For example, the most pronounced fabrication faults are hot cracks. Recently, DMWs have used the various of heat source to decrease such as faults. In this paper, the weldability on dissimilar metal welds of Austenite stainless steel and Low carbon steel using a continuous wave Nd:YAG laser was experimentally investigated. Experiments were conducted to determine effects of welding parameters, on eliminating or reducing the extent welding zone formation at dissimilar metal welds and to optimize those parameters that have the most influence parameters such as focus length, power, beam speed, shielding gas, and wave length of laser.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.13 no.6
• /
• pp.119-126
• /
• 2004

The welding characteristics of Inconel 600 Alloy using a continuous wave Nd:YAG laser are experimentally investigated. The major process parameters studied in the present laser welding experiment were the positions of focus, laser power and travel speed of laser bean We measured the fusion zone size and its shape using an optical microscope for the observation of cross-sectional area. We performed two tests regarding the tension and the micro hardness for welding quality estimation. Then we measured residual stress in welds by electronic speckle pattern interferometry(ESPI). In conclusion the optimum butt welding process parameters were 0.5mm focus position, 1.6kW laser power, 1m/min travel speed and 5.5$\ell$/min assist gas discharge.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.17 no.1
• /
• pp.120-125
• /
• 2008

A flip-chip bonding system using DPSS(Diode Pumped Solid State) Nd:YAG laser(wavelength : 1064nm) which shows a good quality in fine pitch bonding is developed. This laser bonder can transfer beam energy to the solder directly and melt it without any physical contact by scanning a bare chip. By using a laser source to heat up the solder balls directly, it can reduce heat loss and any defects such as bridge with adjacent solder, overheating problems, and chip breakage. Comparing to conventional flip-chip bonders, the bonding time can be shortened drastically. This laser precision micro bonder can be applied to flip-chip bonding with many advantage in comparison with conventional ones.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.21 no.5
• /
• pp.814-823
• /
• 2012

Fluctuation of light intensity from the keyhole becomes more significant in full penetration welding than partial penetration welding, since the plasma produced in the keyhole can escape from the rear side of the keyhole. The plasma optical radiation emitted during Nd:YAG laser welding of S45C steel samples has been detected with a Photodiode and analyzed under different process conditions. As the results, the BOP was performed for welding, behavior of plasma, spatter or plume was monitored to determine the reference signal. Then, random combination was made for comparison with the reference signal, which aimed at verifying reliability of the welding monitoring system that this study intended to develop.

• Laser Solutions
• /
• v.3 no.2
• /
• pp.45-51
• /
• 2000

In this paper, the possibilities and the limits of the laser seam welding were studied to utilize the advantageous properties of amorphous metal foils. For the conventional welding method, the high heat transfer makes the crystallized zone of the work material unavoidable. The laser is able to weld the amorphous metal without a crystallized zone, because heat transfer is limited within a very small restricted volume. The crystallized zone is restricted in the neighbor of welding spot and not in the melting area. This can be proved directly by the etching and indirectly by the tensile shear test, micro hardness test and bending test. The overlapping of welding bead could form the formation of wider and thicker amorphous zone.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.13 no.3
• /
• pp.7-10
• /
• 1976

To eliminate some difficulties encountered in the operation of $LiNbO_3$ crystal as a Q-switch for generating a single pulse Nd-YAG laser, the operational characteristics of the crystal, was investigated. Also a simple method for solving the difficulties was presented.

• Proceedings of the Optical Society of Korea Conference
• /
• 2000.02a
• /
• pp.46-47
• /
• 2000

고출력, 고효율, 그리고 고품질의 빔특성을 갖는 DPSSL을 개발하기 위해서는 출력빔을 저하시키는 원인인 비균일한 여기빔 분포에 의한 레이저 결정내의 열렌즈, stress 복굴절 등의 효과를 최소화하여야 한다. 지금까지 열효과를 줄여, 고출력이나 TE $M_{00}$ 모드의 레이저 빔을 얻기위한 방법으로 zigzag 슬랩 디자인$^{1)}$ , VPS 여기 시스템$^{2)}$ , Cusp 형 반사체$^{(3)}$ , 광섬유 결합$^{(4)}$ 등의 방법이 연구되어 왔다. 본 연구에서는 고출력, 고효율, 그리고 고품질의 레이저 빔특성을 동시에 만족하는 레이저를 개발할 목적으로 산란된 여기빔을 이용하는 여기구조를 고안하고 열효과가 감소된 Nd:YAG 레이저 시스템을 최적설계하였다. (중략)략)

• Laser Solutions
• /
• v.11 no.3
• /
• pp.16-20
• /
• 2008

The lap Joint welding of 6K21 aluminum sheets by Nd:YAG laser were performed with an aluminum 5183 filler wire or without a filler wire. The porosity of laser welding beads were observed through an optical microscope and X-ray photography with various levels of welding speed and gap size. The porosity was observed in the gap between upper and lower sheet near a heat affected zone when autogenous welding. Decrease of welding speed and use of AA5183 filler wire reduced porosity significantly.