• 한국군사과학기술학회지
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• 제19권6호
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• pp.690-697
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• 2016

EOIS(electro-optical imaging system) is the main target of the laser weapon. Specially, the image sensor will be vulnerable because EOIS focuses the incident laser beam onto the image sensor. Accordingly, the laser-induced damage of the image sensor needs to be identified for the counter-measure against the laser attack. In this study, the laser-induced damage of the CCD image sensor irradiated by the CW(continuous wave) NIR(near infrared) laser was experimentally investigated and mechanisms of those damage occurrences were analyzed. In the experiment, the near infrared CW fiber laser was used as a laser source. As the fluence, which is the product of the irradiance and the irradiation time, increased, the permanent damages such as discoloration and breakdown appeared sequentially. The discoloration occurred when the color filter was damaged and then the breakdown occurred when the photodiode and substrate were damaged. From the experimental results, LIDTs(laser-induced damage thresholds) of damages were roughly determined.

• 한국재료학회지
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• 제30권7호
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• pp.327-332
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• 2020

Laser induced surface activation (LISA) technology requires refined selection of process variables to fabricate conductive microcircuits on a general polymer material. Among the process variables, laser mode is one of the crucial factors to make a reliable conductor pattern. Here we compare the continuous wave (CW) laser mode with the pulse wave (PW) laser mode through determination of the surface roughness and circuit accuracy. In the CW laser mode, the surface roughness is pronounced during the implementation of the conductive circuit, which results in uneven plating. In the PW laser mode, the surface is relatively smooth and uniform, and the formed conductive circuit layer has few defects with excellent adhesion to the polymer material. As a result of a change of laser mode from CW to PW, the value of Ra of the polymer material decreases from 0.6 ㎛ to 0.2 ㎛; the value of Ra after the plating process decreases from 0.8 ㎛ to 0.4 ㎛, and a tight bonding force between the polymer source material and the conductive copper plating layer is achieved. In conclusion, this study shows that the PW laser process yields an excellent conductive circuit on a polymeric material.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1990년도 하계학술대회 논문집
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• pp.451-454
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• 1990

Room temperature cw operations of a standing wave and a unidirectional Ti:Sapphire laser pumped by a $Ar^+$ laser have been demonstrated in the same pumping cavity configuration. Laser emission at 790 nm was excited with all-line $Ar^+$ laser pump for both cavities. The maximum output power was found to be 600 mW in the standing wave cavity and 210 mW in the ring cavity. Values of (83 ${\pm}$ 10) % for the internal quantum efficiency and (3.0 ${\pm}$ 0.5) % for the round-trip cavity loss for standing wave cavity are obtained from the thresholds and slope efficiencies measured with 2.4 and 11.2 % optput couplers. The measured cavity-loss value at 790 nm gives a meterial figure of merit (FOM) to be 146. Unidirectional operation of the ring Ti:Sapphire laser will be discussed.

• 한국레이저가공학회지
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• 제12권3호
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• pp.7-13
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• 2009

The process of thermal-degradation of thin-film polymeris studied in this work for various laser sources from CW to fs. Samples composed of a thin polymer layer sandwiched between two glass plates are irradiated by the lasers and the threshold irradiance of polymer carbonization is experimentally measured. In the numerical analysis, the transient temperature distribution is calculated and the number density of carbonization in the polymer layer is also estimated. It is shown that pulsed lasers can result in more uniform distribution of temperature and carbonization than the CW laser.

• 한국광학회:학술대회논문집
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• 한국광학회 1997년도 Advance Program of 14th optics andquantum Electronics conference, 1997제14 회 광학 및 양자전자 학술 발표회 논문 요약집
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• pp.85-85
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• 1997

Czochralski 방법에 의해 육성된 Nd:YAG 단결정으로부터 CW mode의 1064nm laser를 발진시켰다. 육성된 단결정은 직경 50mm, 길이 120mm 이었으며, Nd 이온 농도는 O.2~0.9at% 이었다. 육성된 단결정 boule로 부터 결정학적 결함부위인 core 및 facet가 없는 양질의 단결정 부위를 Twyman-Green interferometer로 선빌하였다. 추출핀 부위는 절단, 가공, 연마공정 및 코팅 공정을 통해 직경 6.35mm, 길이 lOOmm의 laser rod를 제작하였다. 절단은 core drill, 또는 원통 연삭기를 사용하여 rod 형태로 가공하였으며, 상$\cdot$하면 polishing은 평행도 10", 직각도 5', 평활도 $\lambda$/10 수준까지 실험실에서 자체 가공하여 일반적인 laser 발진용 rod의 spec.을 만족시킬 수 있었다.

• Journal of Welding and Joining
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• 제26권5호
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• pp.90-96
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• 2008

The objective of this paper is to investigate the effects of the laser power, the material thickness, comer angles, and the loop size on the formation of the comer in the cutting of Inconel 718 super-alloy sheet using high-power CW Nd: YAG laser. In order to investigate the influence of comer angles and loop sizes on the melted area and the formation of comer in the sharp comer, angular cutting tests and loop cutting tests were carried out. The results of the angular cutting tests were shown that the melted area is minimized and the melting mode is changed from nose melting in the thickness direction to the secondary melting induced by the attached dross when the comer angle is $90^{\circ}$. Through the results of loop cutting tests, the variation of the melted area and the comer shape in the sharp comer according to the loop size were examined. In addition, it was shown that a proper loop size is approximately 3 mm. The results of above experiments will be reflected on the knowledge base to generate optimal cutting path of the laser.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.219-220
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• 2006

Laser surface hardening technologies have been used to improve characteristics of wear and to enhance the fatigue resistance for mold parts. The objective of this research work is to investigate the influence of the process parameters, such as power of laser and defocused spot position, on the characteristics of laser surface hardening for the case of SKD61 steel. CW Nd:YAG laser is selected as the heat source. The optical lens with the elliptical profile is designed to obtain a wide surface hardening area with a uniform hardness. From the results of the experiments, it has been shown that the maximum hardness is approximatly 740 Hv when the power, focal position and the travel of laser are 1,095 W, +1mm and 0.3 m/min, respectively. In addition, the hardening width using the elliptical lens was three time larger than that using the defocusing of laser beam.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2013년도 춘계학술대회 논문집
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• pp.731-732
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• 2013

• 한국광학회지
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• 제4권3호
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• pp.289-293
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• 1993

파장 792 nm의 AlGaAs 레이저 다이오드로 펌핑되는 Nd:YLF 레이저를 제작하여 펌핑세기와 펌핑빔의 파장에 대한 출력특성을 조사하였다. Brewster 각으로 되어있는 Nd:YLF봉에서 발생하는 비점수차를 보정하기 위하여 공진기 구조를 접힌형태로 하였다. 연속 출력 2.6Watt로 펌핑하였을 때 발진파장 1053 nm에서 최대 출력 1.1Watt를 얻었으며, 이때 전체효율이 39% 였다.

• 한국음향학회지
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• 제30권1호
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• pp.33-41
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• 2011

음압을 감지할 수 있는 Sagnac 간섭계 센서와 온도 및 스트레인을 측정할 수 있는 FBG센서를 결합한 새로운 형태의 하이브리드 광섬유 센서 시스템을 구축하기 위하여 입력 광원인 CW를 TLS로 대체할 필요가 있어 이에 따라 광원의 변화와 맨드릴 재료의 변화에 따른 광섬유 센서의 응답 특성 연구가 필요하게 되었다. 제작된 맨드릴 재료는 PTFE와 PTFE에 카본을 섞어 만든 두 종류로 선택하여 중공 원통형 맨드릴 겉면에 광섬유를 18 m 감아 광섬유 센서로 제작하였다. CW 광원에 대하여 음원의 입력 주파수를 1 kHz~20 kHz까지 바꾸어 가며 트랜스포머 오일이 채워진 유조에서 실험하였다. 또한 FBG와 맨드릴형 광섬유 센서를 결합한 하이브리드형 광섬유 센서 시스템을 구성하고 TLS 광원을 입사광으로 실험하였다. 실험 결과 PTFE 센서의 탐지 크기는 카본 센서 탐지 크기보다 높게 나타났고 맨드릴 재질의 탄성계수 값이 적을수록 커진다는 이론 결과와 잘 일치함을 보였다. CW 광원과 TLS 광원에서 응답한 PTFE 센서의 특성을 주파수별로 상호 비교하여 보면 광원이 CW일 때 보다 TLS일 때 응답 특성이 우수함을 알 수 있었다. 본 연구를 통하여 TLS를 이용한 광섬유 센서는 FBG와의 하이브리드 시스템에 적용 가능하리라 사료된다.