• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제53권8호
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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.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제52권12호
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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.

• 한국진공학회지
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• 제13권2호
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• pp.59-64
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• 2004

반도체 레이저를 광원으로 사용하는 원자흡수분광 방법으로 금속증기의 증착 공정을 감시하는 연구를 수행하였다. 전자빔 가열 방식을 이용하여 gadolinium (Gd) 금속을 대량으로 증발시켰다. 파장 영역이 770-794 nm (중심파장 780 nm)인 반도체 레이저빔과 388-396 nm 영역의 제 2 고조파 빔을 진공용기에 입사시켜 증발되는 금속증기의 원자흡수 스펙트럼을 실시간으로 기록하였다. 흡수 스펙트럼을 분석하여 증기의 원자밀도를 구했다. 전자빔 출력을 변화시키면서 측정한 원자밀도를 수정 결정 모니터 장치를 사용하여 측정한 증착률과 비교하였다. 산업적으로 많이 사용되는 Ti 등의 증착 공정 감시에 이 실험에서 구현한 레이저 분광장치를 적용할 수 있다는 것을 제시하였다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제54권5호
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• pp.190-197
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• 2005

A reliable and compact pulse power supply using a thyratron and a magnetic pulse compression (MPC) 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 conventional thyratron-discharge type pulse power supply. A thyratron generated a long pulse of its conduction pulse width 500 ns and then it was compressed to less than 80 ns of its output voltage rise time by a three stage MPC circuit. This pulse power supply was applied to a laser plasma tube of 30 mm inner diameter and 1.5 m discharge length. It was operated several hundreds hours without any troubles.

• 한국전기전자재료학회논문지
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• 제33권5호
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• pp.367-372
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• 2020

As packaging processes for atomic gyroscope vapor cells, the glass tube tip-off process, anodic bonding, and paste sealing have been widely studied. However, there are stability issues in the alkali metal which are caused by impurity elements and leakage during high-temperature processes. In this study, we investigated the applicability of a vapor cell low-temperature packaging process by depositing Au on a Pyrex cell in addition to forming an Au-Sn thin film on a cap to cover the cell, followed by laser irradiation of the Au/Au-Sn interface. The mechanism of the thin film bonding was evaluated by XRD, while the packaging reliability of an Ne gas-filled vapor cell was characterized by variation of plasma discharge behavior with time. Furthermore, we confirmed that the Rb alkaline metal inside the vapor cell showed no color change, indicating no oxidation occurred during the process.

• Journal of the Optical Society of Korea
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• 제16권3호
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• pp.313-317
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• 2012

We have evaluated a 1.3 ${\mu}m$ vertical-cavity surface-emitting laser (VCSEL), whose bottom mirror and central active layer were grown by metal organic chemical vapor deposition (MOCVD) and whose top mirror was covered with a dielectric coating, for 10 Gb/s data transmission over single-mode fibers (SMFs). Successful demonstration of error-free transmission of the directly modulated VCSEL signals at data rate of 10 Gb/s over a 10 km-long SMF was achieved for operating temperatures from $20^{\circ}C$ to $60^{\circ}C$ up to bit-error-rate (BER) of $10^{-12}$. The DC bias current and modulation currents are only 7 mA and 6 mA, respectively. The results indicate that the VCSEL is a good low-power consuming optical signal source for 10 GBASE Ethernet applications under controlled environments.

• Journal of Welding and Joining
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• 제35권2호
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• pp.13-22
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• 2017

In laser full penetration welding process, full penetration hole(FPH) is formed as a result of force balance between the vapor pressure and the surface tension of the surrounding molten metal. In this work, a three-dimensional numerical model based on a conserved-mass level-set method is developed to simulate the transport phenomena during laser full penetration welding process, including full penetration keyhole dynamics. Ray trancing model is applied to simulate multi-reflection phenomena in the keyhole wall. The ghost fluid method and continuum method are used to deal with liquid/vapor interface and solid/liquid interface. The effects of processing parameters including laser power and scanning speed on the resultant full penetration hole diameter, laser energy distribution and energy absorption efficiency are studied. The model is validated against experimental results. The diameter of full penetration hole calculated by the simulation model agrees well with the coaxial images captured during laser welding of thin stainless steel plates. Numerical simulation results show that increase of laser power and decrease of welding speed can enlarge the full penetration hole, which decreases laser energy efficiency.

• 한국정밀공학회지
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• 제22권8호
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• pp.165-173
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• 2005

This paper presents the results for deposition of micrometer-scale metal lines on glass for the development of TFT-LCD circuit repair-system. Although there had been a few studies in the late 1980's for the deposition of metallic interconnects by laser-induced chemical vapor deposition, those studies mostly used continuous wave lasers. In this work, a third harmonic Nd:YLF laser (351nm) of high repetition rates, up to 10 KHz, was used as the illumination source and W(CO)s was selected as the precursor. General characteristics of the metal deposit (tungsten) such as height, width, morphology as well as electrical properties were examined for various process conditions. Height of the deposited tungsten lines ranged from 35 to 500 m depending on laser power and scan speed while the width was controlled between 50um using a slit placed in the beam path. The resistivity of the deposited tungsten lines was measured to be below $1{\Omega}{\cdotu}um$, which is an acceptable value according to the manufacturing standard. The tungsten lines produced at high scan speed had good surface morphology with little particles around the patterns. Experimental results demonstrated that it is likely that the deposit forms through a hybrid process, namely through the combination of photolytic and pyrolytic mechanisms.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 C
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• pp.1210-1212
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• 1994

An amplitude modulation technique for increasing the laser penetration efficiency for metals has been studied. By chopping electro-optically Nd:YAG laser pulse, the threshold energy for reliable hole drilling was decreased significantly and the penetration depth was increased. It was observed that the effect of chopping was optimal at 8-12 kHz with 60% duty cycle. It is believed that this improvement is due to an increase in the vapor recoil pressure and reduced plasma screening.

• 한국광학회지
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• 제4권1호
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• pp.47-56
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• 1993

증기상태의 원자 Au, Ba, Cu, Fe, Mn, Pb, Tl을 모기체로 하는 펄스형 기체방전레이저에 관하여 30ns의 rise time, 펄스반복율 5kHz 방전에 대한 최적동작조건 및 최대효율이 각각 계산되었다. 최적작동온도는 각 원자의 증기압이 대략 1 Torr가 되는 온도이며, 실험에서 보고된 온도범위와 좋은 일치를 보여 주었다. 효율을 최대로 하는 충전전압은 특히 효율이 낮은 Tl을 제외하고는 대락 4kV 정도의 값에서 얻어졌다. 각 레이저의 실질적인 한계효율로서 검토될 수 있는 최대효율은 보고된 실험값 보다 상당히 높은 값으로 계산되었다. 특히, Ba 레이저와 Mn 레이저의 효율은 각각 6.8%, 15%로서 구리증기레이저의 효율 8.5%와 비교할 만한 값이며 실험적으로 보다 높은 효율이 얻어질 수 있음을 예측할 수 있다. 반면에, Tl레이저는 대단히 낮은 효율 0.058%와 예외적인 동작조건을 보여주었다.