레이저유도 습식에칭에 의한 고세장비 마이크로채널 제조

오광환,이민규,정성호 한국레이저가공학회 2005 한국레이저가공학회 학술대회 논문집 Vol.2005 No.11

이득스위칭을 이용한 650nm InGaAIP FP LD의 광펄스 파라메터 분석 및 CW 발진과의 특성비교

오광환,채정혜,이용탁,백운출,김덕영 한국광학회 2001 한국광학회지 Vol.12 No.2

최근 플라스틱 광섬유(Plastic Optical Fiber, POF)가 홈 네트워크(Home Network) 및 LAN(Local Area Network)의 새로운 통신채널로 등장하였다. 특히 PMMA 계에 기반을 둔 언덕형 굴절률 분포 플라스틱 광섬유(Graded Index Plastic Optical Feiber)는 500nm와 650nm 근처에서 아주 적은 손실을 가지므로 이 파장영역에서의 광원으로서 극초단 광펄스 생성이 요구되고 있다. 본 연구에서는 650nm InGaAIP FP(fabry perot) LD와 간단한 RF(radio frequency)소자들을 이용한 회로를 구성하고 이득스위칭 기술을 사용하여 1GHz의 펄스 반복율을 가지고 33.3psec 정도의 짧은 반치선폭(FWHM)을 가지는 광펄스를 생성시키는데 성공하였다. 이득스위칭 된 광펄스는 주입되는 직류전류(DC bias current)와 변조되는 주파에 따라 반치선폭은 33.3-82.8 psec, 펄스 에너지는 0.97-9.69pJ의 값을 얻었다. 또한 CW 발진과 이득스위칭 된 광펄스의 스펙트럼 폭은 각각 0.44nm, 150nm로 됨을 측정하였다. 이러한 결과를 가지는 연속적인 광펄스는 직류전류와 VCO에 의한 변조주파수의 적절한 선택에 따라 초고속 근거리 광통신분야 뿐만 아니라 여러 가지 초고속 광소자 및 전자소자의 특성평가 등에 응용될수 있을 것으로 예상된다. Recently, plastic optical fiber draws a lot of attention as a new transmission medium for local area network (LAN) and home network applications. As PMMA based GI-POF (Graded Index Plastic Optical Fiber) has very low loss at about 500 nm and 650 nm wavelengths, it is very important to have a compact ultra short optical pulse source at these wavelength windows. In this paper, we have investigated detailed characteristics of gain switched laser system by using a commercially available low cost RF devices and an InGaAlP Fabry Perot semiconductor laser operating at 650 nm wavelength. The shortest optical 'pulse obtained was 33 psec with 1 GHz repetition rate. Depending on the DC bias current and the modulation frequency, the FWHM and the pulse energy of the gain switched pulses show 33.3-82.8 psec and 0.97-9.69 pI respectively. Also, the spectral bandwidths for CW and gain switched operations are 0.44 nm and 1.50 nm. We believe that these results are quite useful for high bit rate optical transmission applications with PMMA based plastic optical fibers in addition to estimate properties of ultra fast optical components and electro-optic devices. vices.

방산인력 기술유출 방지를 위한 실태분석 및 개선방안

오광환,김권일,차정훈 한국산업보안연구학회 2021 한국산업보안연구 Vol.11 No.1

The importance of protecting defense technology is critical as the defense industry has grown rapidly, with the recent increase in exports of the defense industry, and various efforts are being made by enacting the Act of Defense Industry Technology Protection in 2015. However, according to the statistics released by the National Intelligence Service and other agencies, more than 80 percent of technology leaks are mainly caused by former and current employees who know the internal situation. Therefore, it is urgent to prepare effective measures to achieve the national security purpose of defense industry technology protection and to prevent technology leakage by defense personnel. In order to prevent technology leakage by defense industry personnel, this study conducted a survey to check the currentstatus of technology leakage, law and systems on defense industry personnel management, and SWOT analysis. Based on the problems, the government proposed measures to revise laws, such as strengthening punishment, establishing comprehensive plans, establishing control towers, strengthening expertise through establishing education systems, and strengthening human resources management. Through this study, we will form a consensus on the seriousness of technology leakage accidents by defense industry personnel, improve laws and systems, and organize defense industry personnel manage systems to minimize technology leakage by defense industry personnel, and further contribute to national security. 최근 방위산업의 수출이 증가하는 등 방위산업이 급격한 성장을 이루면서 방산기술보호의 중요성이 중대되고 있으며 '15년 「방위산업기술 보호법」 제정을 통해 법적 기반을 마련하는 등의 다양한 노력을 진행하고 있다. 하지만 국가정보원 등 각 기관에서 발표한 기술유출 통계를 살펴보면 기술유출의 80% 이상은 내부의 사정을 면밀히 알고 있는 전ㆍ현직 직원에 의해 주로 발생하고 있으며, 최근 국방과학연구소에서 발생한 퇴직 연구원에 의한 기술유출 사고는 기존의 기술적ㆍ물리적 위주의 보안대책이 많은 한계가 있는 것을 보여주고 있다. 따라서 방위산업기술보호의 국가안전보장 목적을 달성하고 방산인력에 의한 기술유출을 예방하기 위하여 효과적인 방안 마련이 시급하다고 할 수 있다. 이에 본 연구는 방산인력에 의한 기술유출을 방지하기 위해 기술유출 현황, 방산인력 관리에 대한 법령 및 제도에 대한 실태분석과 방위산업체의 인력 관리실태를 확인하기 위한 설문조사 결과를 바탕으로 방산인력 관리에 대한 SWOT 분석을 실시하였다. 이에 따라 도출된 문제점 바탕으로 이를 개선하기 위하여 처벌 강화 등의 법령 개정, 종합계획 수립, 컨트롤 타워 설립 등의 정책적 관리 강화, 교육체계 확립 및 자격제도 운영을 통한 전문성 강화, 인력 관리 프로세스를 적용한 핵심인력 관리 강화 등의 개선방안을 제시하였다. 따라서 본 연구를 통해 방산인력에 의한 기술유출 사고의 심각성과 대책 마련에 대한 공감대를 형성하고, 법령 및 제도 개선과 방산인력 관리 체계 정립으로 방산인력에 의한 기술유출을 최소화하여 국가안전보장 및 방산보안 발전에 기여하고자 한다.

Manufacturing Process of Copper Microgrooves Utilizing a Novel Optical Fiber-Based Laser-induced Etching Technique

오광환,임현택,임현덕,정성호 한국정밀공학회 2009 International Journal of Precision Engineering and Vol. No.

A new approach for the fabrication of copper microgrooves with near triangular cross-sectional profile is introduced. For manufacturing the microgrooves, a laser-induced thermochemical etching technique based on an optical fiber as an optical waveguide and machining tool is proposed, which significantly reduced the complexity of a conventional laser etching set up. It is explained that the possible problem of fiber damage during laser etching with the proposed method can be solved by appropriately controlling the gap between the sample surface and fiber tip. The fabrication of copper microgrooves with 100 ~ 300 μm in depth and 100 ~ 150 μm in width is accomplished with the proposed technique. The grooves fabricated in the optimal process condition have smooth surfaces and clear edge. The angle of triangular groove is measured to be in the range of 30 ~ 50 degree and the aspect ratio of grooves is about 1 ~ 2. The overall etching results such as etch width, depth, and aspect ratio variation are reported in detail with respect to process variables.

마이크로 열소자 제작을 위한 고세장비 금속채널의 레이저 가공

오광환,이민규,정성호,Oh, Kwang-Hwan,Lee, Min-Kyu,Jeong, Sung-Ho 한국광학회 2006 한국광학회지 Vol.17 No.5

본 연구에서는 레이저유도 에칭기술을 이용한 스테인레스강의 고세장비 미세채널 제조에 대하여 기술한다. 공정 변수 최적화와 반복에칭을 통하여 높은 세장비를 갖는 미세채널을 제조하였으며 제조된 미세채널은 레이저출력과 에칭용액의 농도를 적절하게 조절함으로써 U 형상과 V 형상 사이의 단면 구조를 가지며 열변형이 없는 우수한 표면 형상을 보였다. 채널과 채널 사이의 간격은 $150{\mu}m$ 또는 그 이하이며 $15{\sim}50{\mu}m$ 범위의 폭을 갖는 10 이상의 고세장비 미세채널이 제조되었다. 레이저출력, 레이저초점의 이송속도, 에칭용액의 농도 등의 공정 변수들이 제조된 채널의 폭, 깊이 그리고 단면 형상에 미치는 영향에 대하여 자세히 보고한다. A fabrication method fur high-aspect-ratio microchannels in stainless steel using laser-assisted thermochemical wet etching is reported in this paper. The fabrication of deep microchannels with an aspect ratio over ten is realized by applying a multiple etching process with an optimization of process conditions. The cross-sectional profile of the microchannels can be adjusted between rectangular and triangular shapes by properly controlling laser power and etchant concentration. Excellent dimensional uniformity is achieved among the channels with little heat-affected area. Microchannels with a width ranging from 15 to $50{\mu}m$ can be fabricated with an aspect ratio of ten and a pitch of 150 m or smaller. The effects of process variables such as laser power, scan speed, and etchant concentration on the fabrication results, including etch width, depth, and cross-sectional profile are closely examined.

Characteristics of metal-induced crystallization (MIC) through a micron-sized hole in a glass/Al/SiO₂/a-Si structure

오광환(Oh, Kwang H.),정혜정(Jeong, Hyejeong),지은옥(Chi, Eun-Ok),김지찬(Kim, Ji Chan),부성재(Boo, Seongjae) 한국신재생에너지학회 2010 한국신재생에너지학회 학술대회논문집 Vol.2010 No.06

Aluminum-induced crystallization (AIC) of amorphous silicon (a-Si) is studied with the structure of a glass/Al/SiO₂/a-Si, in which the SiO₂ layer has micron-sized laser holes in the stack. An oxide layer between aluminum and a-Si thin films plays a significant role in the metal-induced crystallization (MIC) process determining the properties such as grain size and preferential orientation. In our case, the crystallization of a-Si is carried out only through the key hole because the SiO₂ layer is substantially thick enough to prevent a-Si from contacting aluminum. The crystal growth is successfully realized toward the only vertical direction, resulting a crystalline silicon grain with a size of 3{sim}4{mu}m under the hole. Lateral growth seems to be not occurred. For the AIC experiment, the glass/Al/SiO₂/a-Si stacks were prepared where an Al layer was deposited on glass substrate by DC sputter, SiO₂ and a-Si films by PECVD method, respectively. Prior to the a-Si deposition, a 30{times}30 micron-sized hole array with a diameter of 1{sim}2{mu}m was fabricated utilizing the femtosecond laser pulses to induce the AIC process through the key holes and the prepared workpieces were annealed in a thermal chamber for 2 hours. After heat treatment, the surface morphology, grain size, and crystal orientation of the polycrystalline silicon (pc-Si) film were evaluated by scanning electron microscope, transmission electron microscope, and energy dispersive spectrometer. In conclusion, we observed that the vertical crystal growth was occurred in the case of the crystallization of a-Si with aluminum by the MIC process in a small area. The pc-Si grain grew under the key hole up to a size of 3{sim}4{mu}m with the workpiece.

MPDS 웜기어의 효율인자 분석과 효율예측 모델 개발

오광환(K. H. O),김성한(S. H. Kim),변정원(J. W. Byun),신민철(M.C. Shin),주종남(C.N. Chu) 한국정밀공학회 2009 한국정밀공학회 학술발표대회 논문집 Vol.2009 No.6월

KSCN이 함유된 용액에서 레이저유도 에칭된 구리 마이크로 구조물의 특성

오광환(Kwang H. Oh),조석인(S. I. Cho),정성호(S. H. Jeong) 한국레이저가공학회 2007 한국레이저가공학회 학술대회 논문집 Vol.2007 No.-

  A fabrication technique of copper microgrooves with triangular cross-sectional profile using the laser-assisted etching is introduced. To simplify the complex setup of a conventional objective lens-based laser micromachining, a novel optical fiber-based laser-assisted etching system is proposed to manufacture metallic microgrooves. In the new laser micromachining system, the optical fiber plays a key role as a light waveguide and machining tool. The mixture of H₂SO₄ and H₂O₂ included 0.1% KSCN is chosen as the optimal etchant for manufacturing copper microgroove without background etching in the non-irradiated area. The fabrication of copper microgroove with 100~300㎛ in depth and 100~150㎛ in width is achieved with the proposed machining technique. The grooves fabricated at the optimal process condition have smooth surface and clear edge. The angle of triangular groove is measured to be in the range of 30~50 degree and the aspect ratio of grooves is about 1~2. The overall etching characteristics are investigated with respect to process parameters in this paper.

레이저유도 에칭을 이용한 고세장비 마이크로채널 가공 및 응용

오광환(Kwang H. Oh),이민규(M. K. Lee),김수근(S. G. Kim),임현택(H. T. Lim),정성호(S. H. Jeong) 한국정밀공학회 2006 한국정밀공학회 학술발표대회 논문집 Vol.2006 No.5월

High-aspect-ratio(max. 12.5) microchannels with excellent surface quality and good shape uniformity have been realized utilizing laser-induced etching technique. Etch width and depth variations depend largely upon process variables such as laser power and etchant concentration. Etchant concentration in association with viscosity also influence on the cross-sectional profile of the channels. The optimum process conditions for the fabrication of high-aspect-ratio microchannels applicable to micro thermal devices are demonstrated.

섬유/입자 혼합보강 금속복합재료의 피로균열 진전거동

오광환(Kwang-Hwan Oh),양유창(Yoo-Chang Yang),한경섭(Kyung-Seop Han) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.8

The effects of short fiber and particle hybrid reinforcement on fatigue crack propagation behaviors in aluminum matrix composites have been investigated. Single and hybrid reinforced 6061 aluminum containing same 20 Al₂O₃ volume % with four different constituent ratios of short fibers and particles were prepared by squeeze casting method and tested to check the near-threshold and stable crack growth behavior. The fatigue threshold of the composites increased with portion of particle contents and shows the superior crack resistance in low stress intensity range. In stable crack growth region, the slop of Paris' Law which indicating the crack growth rate was independent of microstructure. After allowing for crack closure, the differences in crack propagation rate among the composites were significantly diminished. Observation of the crack path revealed that the fatigue crack propagate mainly to the interfaces and across the hoop direction of short fibers, however crack seldom propagate though the particle for their low aspect ratio. Overall experimental results was shown that Particle reinforcing was enhanced the fracture toughness and fatigue threshold and induced the resistance of crack propagation.