• ETRI Journal
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• v.35 no.3
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• pp.459-468
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• 2013

A novel integrated laser, that is, a distributed reflector laser diode integrated with an electroabsorption modulator, is proposed to improve the output efficiency, single-mode stability, and chirp. The proposed laser can be realized using the selective metalorganic vapor phase epitaxy technique (that is, control of the width of the insulating mask), and its fabrication process is almost the same as the conventional electroabsorption modulated laser (EML) process except for the asymmetric coupling coefficient structure along the cavity. For our analysis, an accurate time-domain transfer-matrix-based laser model is developed. Based on this model, we perform steady-state and large-signal analyses. The performances of the proposed laser, such as the output power, extinction ratio, and chirp, are compared with those of the EML. Under 10-Gbps NRZ modulation, we can obtain a 30% higher output power and about 50% lower chirp than the conventional EML. In particular, the simulation results show that the chirp provided by the proposed laser can appear to have a longer wavelength side at the leading edge of the pulse and a shorter wavelength side at the falling edge.

• Journal of Welding and Joining
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• v.32 no.2
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• pp.63-69
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• 2014

Dual laser heat sources were used for polymer based material joining. An infrared camera and thermocouple DAQ system were used to correlate the temperature distribution to computer simulation. A 50 degree tilted pre-heating laser source was acting as a heating source to promote the temperature to minimize thermal shock by the following a welding heat source. Based on the experimental result, the skin depth was empirically estimated for computer simulation. The offsets of 3mm, 5mm and 10mm split by weld and preheat were effectively used to control the temperature distribution for the optimal laser joining process. The closer offset resulted in an excessive melting or burning caused by sudden temperature rising. The laser power was split by 50%, 75% and 100% of the weld power, and the best results were found at 50% of preheating. To accurately simulate the physical laser beam absorption and joining optical properties were experimentally measured for the computer FEM simulation. The simulation results showed close correlation between theoretical and experimental results. The developed dual laser process is expected to increase productivity and minimize the cost for the final products.

• Journal of the Korean Wood Science and Technology
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• v.25 no.4
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• pp.75-91
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• 1997

Laser cutting tests were conducted to investigate the laser cutting characteristics of solid woods such as 25mm-thick white oak(Quercus acutissima) and maple(Acer mono), and wood-based panels such as 15mm-thick medium density fiberboard and particleboard. Test variables were laser power, cutting speed, grain direction, and moisture content. Cutting depths, kerf widths and the maximum cutting speed were measured. Cutting depths were increased as focus of laser beam was moving from above the workpiece to on the surface of workpiece, and also to below the workpiece. Kerf widths were decreased as focus of laser beam was moving from above the workpiece to on the surface of workpiece, but were increased as focus of laser beam was moving from on the surface of workpiece to below the workpiece. Minimum kerf widths were obtained when focus of laser beam was positioned on the surface of workpiece. Cutting depths and kerf widths were decreased with increase in moisture content, and cutting depths and kerf widths of more dense white oak were smaller than those of maple. And also cutting depths and kerf widths of particleboard were smaller than those of medium density fiberboard.

• The Research Journal of the Costume Culture
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• v.28 no.6
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• pp.738-754
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• 2020

As a cultural feature of, the relics of the Royal Tomb of King Muryeong are suitable design content for applying with sophisticated production and delicate molding laser cutting techniques. The purpose of this study is to develop modern bag designs using relics of the Royal Tomb of King Muryeong of Baekje using laser-cutting techniques. First, the historical background and meaning of Baekje's cultural content were explored. Second, the principle of laser-cutting techniques were explored, laser-cutting techniques applied to modern fashion and bag design were examined, and bag design characteristics were analyzed. Third, based on prior research, the criteria for the development of bag design, from which eight bag design were developed that combine modern popularity and functionality utilizing Baekje cultural content and using laser-cutting techniques to apply the textile design developed by researchers in 2013 (modified to match laser-cutting techniques). The research results show that bag were clutch, tote, shoulder, and mini. Gold, silver, brown, beige, and navy colors were arranged, based on black/white contrast. Cow, lambskin, washed snakeskin, mesh, and Saffiano leather were used. For the pattern-applying technique, this study showed that a new digital technique, which is laser-cutting techniques could be combined with contemporary bag designs. Moreover, a bag design was developed that has a modern sense and functionality as well as Korean formativeness, which is significant.

• Journal of Electrical Engineering and Technology
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• v.12 no.6
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• pp.2353-2358
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• 2017

A femtosecond laser pre-annealing process based on indium zinc oxide (IZO) thin-film transistors (TFTs) is fabricated. We demonstrate a stable pre-annealing process to analyze surface structure change of thin films, and we maintain electrical stability and improve electrical performance. Furthermore, dynamic electrical characteristics of the IZO TFTs were investigated. Femtosecond laser pre-annealing process-based IZO TFTs exhibit a field-effect mobility of $3.75cm^2/Vs$, an $I_{on}/I_{off}$ ratio of $1.77{\times}10^5$, a threshold voltage of 1.13 V, and a subthreshold swing of 1.21 V/dec. And the IZO-based inverter shows a fast switching behavior response. From this study, IZO TFTs from using the femtosecond laser annealing technique were found to strongly affect the electrical performance and charge transport dynamics in electronic devices.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.521-522
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• 2006

Laser additive direct deposition of metals is a new rapid manufacturing technology, which combines with computer aided design, laser cladding and rapid prototyping. The advanced technology can build fully-dense metal components directly from CAD files with neither mould nor tool. Based on the theory of this technology, a promising rapid manufacturing system called "Laser Metal Deposition Shaping (LMDS)" is being developed significantly. The microstructure and mechanical properties of the LMDS-formed samples are tested and analyzed synthetically. As a result, significant processing flexibility with the LMDS system over conventional processing capabilities is recognized, with potentially lower production cost, higher quality components, and shorter lead time.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.25-31
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• 2018

Selective Laser Melting is one of the representative 3D printing techniques for handling metal materials. The main factors influencing the characteristics of structures fabricated by the SLM method include the build-up angle of structures, laser power, laser scan speed, and scan spacing. In this study, the tensile properties of AlSi10Mg alloys were investigated by considering the build-up angle of tensile test specimens, laser scanning speed and scan spacing as variables. The yield stress, tensile strength, and elongation were considered as tensile properties. From the test results, it was confirmed that the yield stress values were lowered in the order of 0, 45, and 90 based on the manufacturing direction of the tensile specimen. The maximum yield stress value was obtained at 1870 mm / min based on the laser scan speed. The yield stress size decreased with decreasing scan speed. Based on the laser scan spacing, as the value increases, the yield stress increases, but the variation is smaller than the other test criteria. The tendency of the tensile strength and elongation variation depending on the test conditions was difficult to understand.

• Mass Spectrometry Letters
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• v.15 no.1
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• pp.26-39
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• 2024

Gold nanostructures (Au NSs) are useful and interesting matrices for mass spectrometric analysis of various biomolecules based on organic matrix-free laser desorption/ionization time-of-flight mass spectrometry (LDI-TOF-MS). Au NSs provide high efficiency and versatility in LDI-TOF-MS analysis based on their well-established synthesis and surface functionalization, large surface area, high laser absorption capacity, and photothermal conversion efficiency. Therefore, Au NSs based LDI-TOF-MS can be a facile, functional, and efficient analytical method for important small biomolecules owing to its simple preparation, rapid analysis, salt-tolerance, signal reproducibility, and quantitative analysis. This review chronologically summarizes the important advance of Au NSs-based LDI-TOF-MS platforms in terms of in-depth mechanism, signal enhancement, quantitative analysis, and disease diagnosis.

• Transactions of Materials Processing
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• v.15 no.4 s.85
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• pp.319-325
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• 2006

The laser forming process is a new flexible forming process without forming tools and external force, which is applied to various fields of industry. Especially, applications of the laser forming process focused on cutting, welding and marking process. In this paper, the laser bending process of sheet metal which is heated by laser beam and formed by internal stress is simulated by using thermo elastic-plastic analysis model. Based on the result of FE-analysis, the laser bending machine is made to obtain reliable data for sheet bending. Under the same condition as FE-analysis, the laser bending experiment has been performed to ver 펴 the result of FE-analysis and good agreement has been obtained between FE-analysis and experiments. Additional laser bending experiments have been performed to evaluate the laser bending machine.

• Laser Solutions
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• v.6 no.3
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• pp.37-45
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• 2003

Pulsed laser ablation is important in a variety of engineering applications involving precise removal of materials in laser micromachining and laser treatment of bio-materials. Particularly, detailed numerical simulation of complex laser ablation phenomena in air, taking the interaction between ablation plume and air into account, is required for many practical applications. In this paper, high-power pulsed laser ablation under atmospheric pressure is studied with emphasis on the vaporization model, especially recondensation ratio over the Knudsen layer. Furthermore, parametric studies are carried out to analyze the effect of laser fluence and background pressure on surface ablation and the dynamics of ablation plume. In the numerical calculation, the temperature, pressure, density, and vaporization flux on a solid substrate are obtained by a heat-transfer computation code based on the enthalpy method. The plume dynamics is calculated considering the effect of mass diffusion into the ambient air and plasma shielding. To verify the computation results, experiments for measuring the propagation of a laser induced shock wave are conducted as well.