• Korean Journal of Optics and Photonics
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• v.17 no.2
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• pp.198-202
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• 2006

Resonator stability condition, $M^2$ beam quality factor, and laser output power are analyzed for two types of two-rod Nd:YAC lasers with rod-end curvatures. Two laser rods with rod-end curvatures are positioned closely to each other or placed separately near each resonator mirror. Experimentally, the output powers and $M^2$ beam quality factors of those lasers are measured with and without thermal birefringence compensation, and compared to numerical analyses.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.6
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• pp.885-890
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• 2015

LLC resonant converter has been widely used because of its high efficiency and high energy density. In this paper, we designed a LLC resonant converter as the main power supply of the Nd:YAG pulse laser. First harmonic approximation (FHA) is used to model the LLC resonant converter. FHA equivalent circuit model and the transfer function of the LLC resonant converter is proposed. Soft start technology is also used to suppress the surge current. The laser output simulation test result is identical with the practical test, the laser energy of every pulse can reach up to 2.5J, and the pulse per second (PPS) can be adjusted from 6 to 18. The power system is verified stable and reliable by both of the simulation and experiment results.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2005.11a
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• pp.177-183
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• 2005

In this work, Inconel 600, Inconel 625 and Haynes 230 are welding using Nd:YAG laser and electron bear. These heat-resistant alloys are typically used for the liquid thruster. To examine, the affects of experimental parameters on weld ability, the plate welding of these materials were carried out using both Nd:YAG laser and electron bear. Also, the micro-structure, micro-hardness, and tensile strength of the specimens were analyzed. from the analysis of the experimental results of laser and electron beam welding, we have obtained the optimal welding conditions.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.6
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• pp.988-997
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• 2012

Laser surface hardening is one of core technologies to enhance various characteristics such as the strength, hardness, toughness, abrasion resistance, and fatigue resistance for the mold material. This paper focuses on testing characteristics of the laser heat treatment according to the preheating parameters in case of the SM45C medium carbon steel. In this paper, we assume that the power and travel speed of the laser are 1,800W and 0.5m/min, respectively, and the range of the preheating temperature is $50^{\circ}C{\sim}300^{\circ}C$. From the result of the test, we observed that the hardness width and depth are enhanced as the temperature is increased. Also, the best average hardness was 751.7Hv for the temperature of $100^{\circ}C$.

• Applied Science and Convergence Technology
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• v.26 no.4
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• pp.66-69
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• 2017

Physically implanted surface islands of Nano Carbon Tube (NCT) and ${\alpha}-F_2O_3$ particles have been produced on Al-doped ZnO (AZO)/glass surfaces by simple and direct ND:YAG laser beam irradiation. Sheet resistance of the reconstructed surface increased by about 3.6% of over AZO. Minimal surface damage can be repaired by ND:YAG laser beam irradiation in conjunction with proper impurities. Implanted islands of NCT, which are considered to be a good conductive impurity, on AZO increased the sheet resistance by about 1.8%, while implanted islands of ${\alpha}-F_2O_3$, an insulating impurity, on AZO increased sheet resistance by about 129% compared with a laser beam treated AZO. This study provides insight regarding surface implantations of nanowires and micro-circuits, doping effects for semiconductors and optical devices, surface area and impurity effects for catalysis.

• Journal of Welding and Joining
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• v.26 no.5
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• pp.90-96
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• 2008

The objective of this paper is to investigate the effects of the laser power, the material thickness, comer angles, and the loop size on the formation of the comer in the cutting of Inconel 718 super-alloy sheet using high-power CW Nd: YAG laser. In order to investigate the influence of comer angles and loop sizes on the melted area and the formation of comer in the sharp comer, angular cutting tests and loop cutting tests were carried out. The results of the angular cutting tests were shown that the melted area is minimized and the melting mode is changed from nose melting in the thickness direction to the secondary melting induced by the attached dross when the comer angle is $90^{\circ}$. Through the results of loop cutting tests, the variation of the melted area and the comer shape in the sharp comer according to the loop size were examined. In addition, it was shown that a proper loop size is approximately 3 mm. The results of above experiments will be reflected on the knowledge base to generate optimal cutting path of the laser.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.6
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• pp.538-544
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• 2000

The laser patterning of sputter-deposited CoNdZr/Cu/CoNbZr multi-layered films had been tried using Nd:YAG laser. However generally it is very difficult to remove metal films because of their high reflectance of the laser on the surfaces. As a counterproposal for this problem authors for the first time tried to deposit energy-absorbing layers on the metal films and then irradiated the laser on the surfaces of energy-absorbing layers. Here the energy-absorbing layers consisted of laser energy-absorbing fine powders and binding polymers. Three kinds of powders for the energy-absorbing layers had been used to see the difference in the pattern formation with the degree of laser energy absorption. They were electrically conductive silver powders insulating BaTiO$_3$powder and semiconducting carbon powder. Remarkable difference in width of the formed pattern and the roughness of pattern edge were observed with the characteristic of the powder for the energy-absorbing layer. The pattern width using carbon paste was about three times larger than that using BaTiO$_3$paste. It was observed that the energy-absorbing layer with carbon was the most effective on this micro-patterning.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.331-331
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• 2011

We investigated the surface roughness and surface morphology changes for the laser irradiated alumina plates by a Q-switched Nd:YAG laser. For the laser irradiation on the alumina plates with ${\lambda}$ = 1064 nm, the surface roughness decreases with the increasing energy density. The surface morphology shows that the edges of alumina grains become dull with the increasing energy density. For ${\lambda}$ = 532 nm, increasing scan time at the same energy density causes a rough surface. We discuss the physical reason of the surface roughness and surface morphology changes.

• Laser Solutions
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• v.3 no.3
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• pp.31-37
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• 2000

In this paper, the possibilities of the laser overlap spot welding were studied to utilize the advantageous properties of amorphous metal foils. In order to estimate the usage of amorphous metals foils as structural members, the tensile shear strength and the fracture features were investigated. Although the crystalline zone on the surface was formed, it was not the direct cause of the fracture of the weld. The fracture of the weld resulted from the geometry discontinuity between the workpiece and the protrusion zone, which was formed during the weld process. The vein pattern - the typical feature of the fracture of the amorphous metal - was formed on the fracture surface. The tensile shear stress was reached to 1200 N/㎟ (2-foils overlap welding) and 900 N/㎟ (10-foils overlap welding), whereas the tensile strength of the workpiece was 1500-2000 N/㎟.

• Tuberculosis and Respiratory Diseases
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• v.41 no.5
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• pp.494-503
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• 1994

Background: Fibrostenosis of large airway due to tuberculosis is one of the most perplexing clinical problems not only because it can lead to respiratory failure but also because of difficulty in the management. No one technique, such as balloon dilatation or insertion of self expandable metallic stent, has proved totally satisfactory in the management of fibrostenosis. We evaluated the effect of laser therapy in patient with severe fibrostenosis due to tuberculosis. Method: We classified the fibrostenosis to three types by bronchoscopic finding - the diaphragm type: stenosed by fibrous diaphragm, sparing the tracheobronchial wall, the collapse type: stenosed by collapse of the wall due to destruction of the cartilage, and the combined type: stenosed by nonspecific inflammatory scar tissue within internal lumen with collapse of the wall. We have treated 10 patients complaining dyspnea due to with severe fibrostenosis of the diaphargm or the combined type using a neodymiumyttrium aluminum garnet(Nd-Y AG) laser through a flexible bronchoscopy. Results: Eight of the 10 cases improved after laser therapy and maintained during a follow up period of average 31.9 months. All of the cases undergoing laser therapy showed no serious complication to need the therapy. Conclusion: The results of our present study indicate that the Nd-YAG laser therapy is an effective and safe method for the management of selective tuberculous fibrostenosis.