• Laser Solutions
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• v.8 no.2
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• pp.21-32
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• 2005

The excimer laser ablation of a polymer occurs by the excitation of chemical bonds to energy levels that are above the dissociation energy. In this process, however, fragmented debris is finally ejected explosively by the scission of bonds and accumulates on the material surface. In the present work, a process for eliminating surface debris contamination generated by the laser ablation of a polymer is developed. The proposed approach for removing surface debris utilizes an erasable ink pasted on a polymide. The ink pasted polyimide is ablated by KrF excimer laser. The surface debris ejected from the polyimide is then combined with the ink layer on the polymer. Finally, both the surface debris and the ink layer are removed using adhesive tape or alcohol solvent. The results suggest that the erasable ink method is a simple, low cost, and extremely effective debris eliminating process.

• Journal of the Korean Society of Safety
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• v.21 no.3 s.75
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• pp.8-15
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• 2006

It is no wonder that mechanical structures are accompanied by problems related to corrosion after being exposed to long hours of work. Corrosion of mechanical structures has been the most serious problem in the field of industry. The present study employed a laser beam irradiation test to improve the corrosion resistance of degraded Cr-Mo steel, which was used for more than 60,000 hours. To find the optimum irradiation test condition for the corrosion resistance of degraded Cr-Mo steel, hardness and residual stress measurements, micro-structural observation, and the electrochemical potentiokinetic reactivation (EPR) tests were performed with changes in laser beam test conditions including laser beam output, diameter, and velocity. Thus, the present study indicates that the optimum test condition and absorption energy for a laser beam test need to be determined to enhance corrosion resistance of degraded Cr-Mo steel.

• Current Optics and Photonics
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• v.3 no.3
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• pp.236-242
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• 2019

An Nd:YAG slab structure was designed for a high-power zigzag slab laser amplifier based on computational simulation of the wavefront distortion. For the simulation, the temperature distribution in the slab was calculated at first by thermal analysis. Then, the optical path length (OPL) was obtained by a ray tracing method for the corresponding refractive index variation inside the slab. After that, the OPL distribution of the double-pass amplified beam was calculated by summing the results obtained for the first and second passes. The amount of wavefront distortion was finally obtained as the peak-to-valley value of the OPL distribution. As a result of this study, the length and position of the gain medium were optimized by minimizing the transverse wavefront distortion. Under the optimized conditions, the transverse wavefront distortion of the double-pass amplified beam was less than $0.2{\mu}m$ for pump power of 14 kW.

• Journal of the Optical Society of Korea
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• v.12 no.4
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• pp.298-302
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• 2008

We have developed a 270-W 15-kHz MOPA system based on side-pumped rod-type Nd:YAG gain modules. The master oscillator is a 3-W 15-kHz $TEM_{00}$ $Nd:YVO_4$ laser with a pulse duration of 30 ns. To preserve the high beam quality during the amplification, we use image relay and polarization rotation which can simultaneously compensate for thermal lensing and thermal birefringence generated in the rod-type gain modules. After the amplification to 270 W with six rod-type gain modules, the beam quality factor ($M^2$) of the amplified laser beam is 5-10, and the pulse duration is maintained at 30 ns.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.1
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• pp.41-47
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• 2012

The LDS(Laser Direct Structuring) is one of the new direct writing methods to fabricate conductive patterns by energy beam. It uses thermoplastic polymers with an additive compound that serves as plating seed after the activation by laser. The advantages of LDS include the miniaturization of electrical components, design flexibility, and a reduced number of production steps. The purpose of this study is to investigate the fundamental mechanism for LDS and the characteristics of conductive patterns by laser parameters. These results were studied by SEM, EDX, and XPS analysis. We have used a 20W pulse-modulated fiber laser and copper electroless plating to fabricate conductive patterns on polymer. The result showed that electroless copper plating seed caused the laser cracking of additive compound. In particular, the additive compound contained in copper metal oxides atoms will be changed to copper metal elements. Also, the characteristics of conductive patterns were dependent on laser parameter, especially laser fluence.

• Korean Journal of Optics and Photonics
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• v.5 no.3
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• pp.386-393
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• 1994

We have investigated output characteristics of XeCI excimer laser excited by transeverse electronbeam. We used e-beam output of 880 kV, 21 kA (70 ns, FWHM) and controlled current density of e-beam by pulsed magnetic coil (4.7 kG) which was fabricated around an e-beam diode (A-K gap is 21 mm) and laser chamber. We have obtained 35 J (4 atm) of e-beam deposition energy injected into laser media. The deposition energy was converted from an exposure area of Radcolor film and rising pressure of gas media which is measured by pressure jump method. The excited volume of $320cm^{3}$ was calculated. The maximum efficiency of 1.7% was obtained with the mixing ratio of HCllXe/Ar==0.2/ 6.3/93.5% and total pressure of 3 atm. Also laser output energy and specific energy were obtained 0.52 J and 1.7 J/I, respectively. For the analysis of experimental results we have developed computer simulation code. From the good agreements with the results of experiment and simulation we could theoretically explain the XeCI* formation channel. relaxation channel, and absorption channel of 308 nm.308 nm.

• Journal of Institute of Convergence Technology
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• v.3 no.2
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• pp.39-43
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• 2013

Titanium has been used to satisfy various applications such as bio engineering, aerospace, electronics, automobile. Recently, micro fabrication technologies of metals such as titanium have been required to satisfy many conditions in various fields. To satisfy these demands, micro electrochemical process using laser marking can be an alternative method because it is one of the precision machining and efficient process. Micro electrochemical process using laser marking needs to accomplish form of the oxidized recast layer on metal surface by laser marking. The laser beam marking conditions such as average power, pulse repetition rate and marking speed should be properly selected to form oxidized recast layer. So, the characteristics of titanium surface according to laser marking conditions was investigated through SEM(scanning electron microscope), EDS(energy dispersive spectrometer) and surface roughness analysis.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1061-1064
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• 2007

Thin Beam Excimer Laser Annealing is investigated as one possible process enabled by the variable concept of Thin Beam LTPS processing. The structure of the resulting p-Si material is analyzed in terms of grain size distribution, scaling with energy density and overlap, as well as average surface roughness. This process provides similar control and latitude as conventional excimer laser annealing, but reduced average surface roughness and the potential to be scaled to significant productivity levels.

• Nuclear Engineering and Technology
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• v.43 no.2
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• pp.133-140
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• 2011

In this paper, a deformation measurement technology for nuclear fuel rods is proposed. The deformation measurement system includes a high-definition CMOS image sensor, a lens, a semiconductor laser line beam marker, and optical and mechanical accessories. The basic idea of the proposed deformation measurement system is to illuminate the outer surface of a fuel rod with a collimated laser line beam at an angle of 45 degrees or higher. For this method, it is assumed that a nuclear fuel rod and the optical axis of the image sensor for observing the rod are vertically composed. The relative motion of the fuel rod in the horizontal direction causes the illuminated laser line beam to move vertically along the surface of the fuel rod. The resulting change of the laser line beam position on the surface of the fuel rod is imaged as a parabolic beam in the high-definition CMOS image sensor. An ellipse model is then extracted from the parabolic beam pattern. The center coordinates of the ellipse model are taken as the feature of the deformed fuel rod. The vertical offset of the feature point of the nuclear fuel rod is derived based on the displacement of the offset in the horizontal direction. Based on the experimental results for a nuclear fuel rod sample with a formation of surface crud, an inspection resolution of 50 ${\mu}m$ is achieved using the proposed method. In terms of the degree of precision, this inspection resolution is an improvement of more than 300% from a 150 ${\mu}m$ resolution, which is the conventional measurement criteria required for the deformation of neutron irradiated fuel rods.

• Laser Solutions
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• v.16 no.4
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• pp.1-6
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• 2013

Femtosecond laser patterning of ITO on a touch screen panel with a shaped fs laser beam was investigated. A quasi flat-top beam was formed using a variable mask and a planoconvex lens. The spatial profile of the original Gaussian beam and the shaped beam were monitored by a CCD beam profiler. The laser patterned ITO film was examined using an optical microscope, Scanning Electron Microscope (SEM) with Energy Dispersive X-ray Spectroscopy (EDS), and Atomic Force Microscope (AFM). It turned out that the quality of the ITO pattern fabricated by a shaped beam is superior to that of the pattern without beam shaping in terms of debris generation, height of the craters, and homogeneity of the bottom. Optimum processing window was determined at the laser irradiance exhibiting 100% removal of Sn. The removal rate of In was measured to be 83%.