• 전기의세계
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• 제31권5호
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• pp.383-390
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• 1982

The high power glass laser system was designed and constracted which consisted of a TEM$\_$00/ mode Q-switching oscillator, a pulse shaping, system, two-stage pre-amplifiers, five-stage main amplifiers, a Faraday rotator, and a uni-guide slit. The laser output of 3OGW with the pulsewidth of 2 nsec was obtained by performing the amplifiing experiment in this system. When the laser light with the pulsewidth of 10 nsec was amplified, the large factor of amplification was obtained in the beginning of pulse, but the factor of amplification decreased gradually in the later part of pulse. Therefore, the laser light which has short pulsewidth of-2nsec must be amplified in order to obtain the larger factor of amplification. When the laser beam from the high power glass laser system was irradiated to plasma, the reflected laser light from plasma which occured inevitably could be attenuated to the order of 10$\^$-4/ by using the Faraday rotator and the uni-guide slit.

• Journal of the Optical Society of Korea
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• 제12권3호
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• pp.178-185
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• 2008

Recent progress in high power lasers enables us to access a regime of high-energy-density and/or ultra-strong fields that was not accessible before, opening up a fundamentally new physical domain which includes laboratory astrophysics and laser nuclear physics. In this article, new applications of high-energy and ultra-intense laser will be reviewed.

• 한국광학회지
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• 제21권6호
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• pp.254-258
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• 2010

타원형 모양의 모드 형태를 갖는 펄스형 레이저 다이오드 (laser diode)의 펄스 형태를 유지하면서 단일 모드 및 Gaussian 형태로 광 모드 변환을 유도하고 광출력을 증폭할 수 있는 기술에 대해서 연구하였다. 실험에서 사용한 펼스형 레이저 다이오드의 구경이 가로는 $300{\mu}m$이며, 세로는 $2{\mu}m$이고 출력은 $1.1mW/cm^2$이다. 렌즈형 광섬유를 사용하여 광결합을 유도하여 단일 모드 및 Gaussian 형태의 출력으로 변환시켰다. 그러나, 다중모드의 펄스형 레이저 다이오드의 출력을 단일모드 렌즈형 광섬유에 결합시키면 출력이 급격하게 감소한다. 따라서 master oscillator power amplifier (MOPA) 기반의 광증폭 기술을 이용하여 레이저 다이오드의 광출력을 증폭시켰다. 증폭 후에도 펄스 성질은 그대로 유지되었고, MOPA구조를 지나 증폭된 광 출력은 $29mW/cm^2$로 측정되었다.

• 한국군사과학기술학회지
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• 제7권4호
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• pp.100-106
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• 2004

The effects of adiabatic flame temperature and mass flux on deuterium fluoride(DF) chemical laser performance were investigated. The power flux and specific power, which are important parameters containing the information of scaling effects of laser device magnitude, and chemical efficiency were selected as a judging parameter of DF laser performance. For the specific power, it was decreased by the increase of power flux of DF laser. Higher the adiabatic flame temperature of atomic fluorine generator, higher the chemical efficiency of DF laser was changed. It seems that the mass flux effect on the chemical efficiency is not remarkable.

• 전기학회논문지
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• 제63권7호
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• pp.924-928
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• 2014

LLC resonant converter is used to control laser power density in ruby laser power supply. Zero voltage switching(ZVS) is implemented to minimize the switching loss by the LLC resonant converter. Laser output power is investigated and experimented by changing the output current. That current is controled by the charging voltage of capacitor. From those results, we obtained the maximum laser output of 1.94J at the discharge current of 860A and the pulse repetition rate of 1Hz.

• 한국레이저가공학회지
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• 제2권2호
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• pp.42-51
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• 1999

This study has been performed to investigate into some effects of the output power and traverse speed of laser beam on the microstructures, hardness and fatigue resistance of the ductile iron surface-hardened by $CO_2$ laser defocussed beam. Optical micrographs have shown that with increasing the output power and decreasing the traverse speed, the martensite was coarsened and some retained austenite were appeared in ductile iron. The microstructures of hardening zone were composed of bull's eye and some nodular graphite dissolved structures by the effect of self quenching. Fatigue fracture characteristics of ductile iron have appeared in the high stress and low stress ranges. The fracture initiated at nodular graphites in the surface hardened layer due to the stress concentration caused by a notch effect. The interior graphite nodules were broken away or popped out during crack propagation. Fatigue test has shown that values of fatigue strength considerably increased with increasing output power at a given traverse speed.

• 대한물리치료과학회지
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• 제7권2호
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• pp.533-543
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• 2000

This study was designed to evaluate the analgesic effect of low power GaAsAl laser on the pain threshold of mechanical stimulation using different treatment points, acupuncture point (zusanli) and non-acupuncture points(back). Furthermore, we investigated the analgesic effect of low power GaAsAl laser using the different duration and intensity of laser in mechanical stimulation induced pain behavior. The results were summarized as follows: 1. The threshold of mechanical stimulation was significantly increased by GaAsAl laser stimulation into zusanli point after 15 and 30 min after laser stimulation(P<05). However, the laser stimulation into non-acupoint did not affect the pain threshold of mechanical stimulation. with dose dependent manner. 2. In order to investigate the analgesic effects of BV depending upon different intensities of laser stimulation, the experimental animals were divided into three groups: 3 mW treated group, 6 mW treated group and 10 mW treated group. The low power GaAsAl laser stimulation was applied into zusanli acupoint for 30 min with different intensity of laser stimulation. Six and ten mW of laser stimulation significantly increased the pain threshold of mechanical stimulation at 15 min after laser stimulation as compared to that of control group(P<.05). Moreover, the analgesic effect of 10 mW laser stimulation was maintained for 30 min after laser stimulation (P<.05). 3. Finally, we tested the analgesic effect of 10 mW laser stimulation using different duration such as 10 min, 30 min or 1 hr after application of mechanical stimulation. In 30 min treatment group, the pain threshold of mechanical stimulation was increased at 15min and 30min after laser stimulation(P<.05). However, laser stimulation for 60 min dramatically increased the pain threshold of mechanical stimulation at 0 min after laser stimulation and the analgesic effect of laser stimulation was observed until 1 hr after laser stimulation. In conclusion, these data apparently demonstrate that low power GaAsAl laser has analgesic effect on mechanical induced pain model in rats. In addition, the treated point, intensity and duration of laser stimulation should be concerned before clinical application for pain management purpose.

• Journal of Welding and Joining
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• 제33권4호
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• pp.1-6
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• 2015

Advances in laser technology have yielded a multitude of innovative processes and applications in various industries. Laser peening is a typical example invented in the mid-1990s as a surface technology, which converted residual stress from tension to compression by just irradiating successive laser pulses to metallic materials under aqueous environment without any surface preparation. The effects of laser peening have been experimentally studied on residual stress, stress corrosion cracking(SCC) susceptibility and fatigue properties with water-penetrable frequency-doubled Nd:YAG laser. In addition, laser peening has been widely used in aviation and aerospace industries, automobile manufacturing and nuclear plant. One of the most important causes to improve the above-mentioned properties is the deeper compressive residual stress induced by laser peening. Taking advantage of the process without reacting force against laser irradiation, a remote operating system was developed to apply laser peening to nuclear power reactors as a preventive maintenance measure against SCC.

• Journal of Welding and Joining
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• 제33권4호
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• pp.17-23
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• 2015

Laser-gas metal arc hybrid welding has been considered as an alternative process of gas metal arc welding for offshore pipe laying. Fiber delivered high power lasers which enable deep penetration welding were recently developed but high power welding characteristics were not fully understood yet. In this study, the influence of shielding gas composition on welding phenomena in high power laser welding was investigated. Bead shapes, melt ejection and dropping were observed after autogenous laser welding with 100% Ar, Ar-20% $CO_2$, Ar-50% $CO_2$, and 100% $CO_2$ shielding gas. Process parameter window was widest with Ar-50% $CO_2$ shielding gas and the penetration was deepest with 100% $CO_2$ shielding gas. The melt dropping was not observed when Ar-50% $CO_2$ or 100% $CO_2$ shielding gas was supplied.

• 한국광학회지
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• 제8권4호
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• pp.291-296
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• 1997

Slot형의 구리 이온 레이저를 제작하여, 780 nm 레이저 동작을 위한 장치구조의 안정성과 특성을 조사했다. 구리 이온 레이저의 최대 출력을 다양한 동작조건 범위에서 측정했다. IR-레이저의 출력은 음극의 기하학적 구조, 방전전압, 그리고 기체압력에 주로 의존했다. 네온의 부분압력이 60%에 이르면 출력이 감소하였으며, 그 이유 중에 하나는 높은 레이저 준위의 Population이 감소했기 때문이다. 파장 780 nm는 레이저 전이가 구리 이온의 5p 준위에서 일어난다. 통형음극을 사용하는 본 실험의 레이저 장치는 헬륨과 네온 흡합기체 방전에서 동작되고, 100시간 동안의 방전시간 후에 출력감소가 35%이었다(활성길이 9.6cm에 대한 출력은 2.8 mW).