• Journal of the Korean Ceramic Society
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• v.35 no.1
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• pp.41-47
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• 1998

Cutting and planarization of diamond films have been performed using copper vapor laser under air at-mosphere. Diamond films of about 350${\mu}{\textrm}{m}$ and 800 ${\mu}{\textrm}{m}$ thick have been synthesized with DC plasma assisted chemical vapor deposition. The position of a specimen has been controlled by computer-driven stage. With copper vapor laser beam of 7W cutting depth increases rapidly and saturates with increasing scan number and decreasing scan speed. 8 repetitive scans at scan speed 0.5 mm/sec produce the maximum cutting depth without focus shifting Rod-shape copper vapor laser beam can be made and used effectively in planar-ization of rough diamond surface.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.12
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• pp.568-572
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• 2003

A longitudinal discharge heated copper vapor laser with internal diameter 28 mm and discharge length 1.3 m has been constructed and tested. At the discharging voltage 15.2 kV, pulse repetition rate 10 kHz, buffer gas pressure 40 mbar, and internal temperature of the laser plasma tube $1520^{\circ}C$, it delivers more than 30 W average laser outputs.

• Journal of the Korean Ceramic Society
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• v.36 no.4
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• pp.417-424
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• 1999

Laser lapping of diamond films is performed with focused beam of copper vapor laser. Both spherical and rod-shape laser beam are used. Diamond surface is scanned at various scan speeds(0,125, 0.5, 0.75 mm/sec) and baem shifts (5, 10, 20, 40, 100$\mu\textrm{m}$) At 0.125 mm/sec 10$\mu\textrm{m}$ scan condition the level difference of di-amond surface of about 700$\mu\textrm{m}$ over 20 mm is reduced to 200$\mu\textrm{m}$ In addition surface roughness is also im-proved from 3.53$\mu\textrm{m}$ to 2.47$\mu\textrm{m}$ at 5$\mu\textrm{m}$ beam shift. But at higher beam shift than 10$\mu\textrm{m}$ laser scan makes the surface rougher which is considered to be due to the non uniform spatial distribution of laser en-ergy. It is concluded that homogenized laser beam with high average power is needed for large area laser lapping of diamond films at appreciable rates.

• Journal of the Korean Ceramic Society
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• v.37 no.2
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• pp.140-144
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• 2000

Laser cutting of thick diamond films is studied using a low-power(10 W) copper vapor laser. Due to the existence of the saturation depth in laser cutting, thick diamond films are not easily cut by low-power lasers. In this study, we have adopted a low thermalconductivity underlayer of alumina and a heating stage (up to 500$^{\circ}C$ in air) to prevent the laser energy from consuming-out and, in turn, enhance the cutting efficiency. Aspect ratio increases twice fromm 3.5 to 7 when the alumina underlayer used. Adopting a heating stage also increases aspect ratio and more than 10 is obtained at higher temperatures than 400$^{\circ}C$. These results show that thick diamond films can be cut, with low-power lasers, simply by modifying the thermal property of underlayer.

• Korean Journal of Optics and Photonics
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• v.10 no.3
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• pp.221-225
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• 1999

The positive branch confocal unstable resonator equipped with an intra-cavity beam splitter has been studied experimentally to achieve low beam divergence in the copper vapor laser. Output laser beams of 0.15 mrad divergence was achieved from the laser system with a 10 cm curvature convex mirror (M=30), and laser beams of 0.1 mrad was achieved for a 5 cm curvature convex mirror (M=60). The power density of the far-field beam from the M=60 resonator laser was 130 times higher than the case of the 2 mrad-operation with the plane-parallel resonator. We also observed the self-mode-locking from the unstable resonator laser pulses.

• Korean Journal of Optics and Photonics
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• v.1 no.1
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• pp.28-32
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• 1990

We have constructed and operated a discharge heated copper vapor laser which generated green (510.6 nm) and yellow (578.2 nm) light. The plasma tube was made of high purity (99.8%) alumina tube which has an inner diameter 25 mm and a length 106 cm. The electrodes, made of molybdenum sheet, were separated 108 cm apart. The laser gave an average power of 10 W at repetition rate of 5 kHz, charging voltage of 10 kV, Ne buffer gas pressure of 40 mbar, and the laser tube temperature of $1500^{\circ}C$..

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.8
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• pp.415-419
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• 2004

A pulse power supply using IGBTs and MPC (magnetic pulse compression) circuit was developed for a metal vapor laser. The life time of the pulse power supply is expected to be much longer than that of a vacuum tube or thyratron type pulse power supply. A series-connected IGBT array generated a long pulse of its pulse width 2 ${\mu}\textrm{s}$ md then it was compressed to less than 100 ns by a three stage MPC circuit. This pulse power supply was applied to a laser plasma tube of 10 mm inner diameter and 0.5 m discharge length. and successfully operated.

• Proceedings of the Optical Society of Korea Conference
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• 1990.02a
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• pp.20-25
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• 1990

• Journal of ILASS-Korea
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• v.5 no.1
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• pp.49-57
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• 2000

This study presents the flow visualization results, velocity and turbulence intensity measurements made within an air filter cover and entry region of a mass air flow sensor (MAFS) which is used in an induction system of 3.8L engine. Flow structure in two air filter cover assemblies were examined. The first was a clear plastic replica of the production cover while the second was a modified clear plastic cover with a geometry configured to reduce fluctuations. High speed flow visualization and laser doppler velocimetry (LDV) systems were used to reveal and analyze the flow field characteristics encountered in the sensor design process under steady flow conditions. A 40-watt copper vapor laser was used as a light source. Its beam is focused down to a sheet of light approximately 1.5mm thick. The light scattered off the particles was recorded by a 16mm high speed rotating prism camera at 5000 frames per second. A comparison of the flow patterns and LDV measurements in the original and modified air filter covers is presented to illustrate the controlling effect of the cover design on the turbulence structure formation near the bypass and on the sensor output signal. In both axial and radial planes of the main passage it was found that the turbulence flow pattern is remarkably influenced by the air filter cover and main passage configuration.

• Korean Journal of Optics and Photonics
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• v.4 no.1
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• pp.47-56
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• 1993

Practical efficiencies of pulsed gas discharge lasers utilizing vaporized Au, Ba, Cu, Fe, Mn, Pb, TI atoms are numerically optimized for a discharge pulse of 30 ns rise time at 5 kHz pulse repetition rate. Calculated optimum operating temperatures are close to the values at which the vapor pressure of each atom is about 1 Torr and are in good agreement with experimental values reported elasewhere. The optimum charging voltage was about 4 kV for all atomic vapor lasers except the TI laser. The calculated maximum efficiencies that have been discussed for possible limiting efficiencies for each laser were considerably higher than the reported experimental values. Especially, they were as high as 6.8% for Mn laser and 15% for Ba laser that were comparable to the 8.5% of copper vapor laser, from which considerably higher efficiencies can be expected for these two lasers experimentally. But, the present calculation shows a very low efficiency of 0.058% and requires an exceptional operating condition for the TI laser.