• 한국광학회지
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• 제13권1호
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• pp.15-20
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• 2002

고리형 반도체 광섬유 레이저에서 외부의 별도 펌프광 없이 4광파 혼합에 의해 파장을 가변할 수 있는 시스템을 구현하였다. -8 dBm의 10 GHz 초단펄스를 입력 신호 광원으로 인가하여 반도체 광증폭기의 이득 대역폭내에서 하향 30 nm및 상향 17 nm에 이르는 연속적인 파장변환을 성공시켰다. 구현된 변환기는 광대역 파장변환 뿐만아니라, 고속 변환 및 낮은 포화 신호전력 특성을 보임을 입증하였다.

• 한국광학회지
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• 제18권5호
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• pp.345-350
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• 2007

광결정 광섬유에서 생성되는 초 연속스펙트럼의 특성을 일반화된 비선형 슈뢰딩거 방정식과 split step 퓨리에 방법을 이용하여 전산모사 하였다. 그 결과를 바탕으로 200 fs 펄스폭을 갖는 Ti:sapphire 레이저와 광결정 광섬유를 이용하여 650nm부터 900nm에 이르는 파장영역에서 ${\pm}4dB$ 이하의 평탄도를 가지는 초 연속스펙트럼을 실험적으로 생성하였다.

• 전기전자학회논문지
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• 제22권2호
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• pp.432-439
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• 2018

본 논문에서는 플렉시블 솔라셀의 수광면을 원통형으로 만들어 수평면상에서 균일한 수광패턴을 가지는 전방향 가시광 검출기를 개발하였다. 이 솔라셀 광검출기는 서로 다른 위치에서 입사하는 여러 개의 신호광을 동시에 검출하며, 수신부의 ASK복조기에 전력을 공급한다. 실험에서는 시분할 전송 방식을 사용하여 서로 다른 방향으로부터 입사하는 3개 신호광을 솔라셀 광검출기로 수신하였다. 각 신호광은 40 kHz의 캐리어를 사용하여 ASK 변조하였으며, 시분할 전송에 필요한 동기펄스는 실내의 조명램프에 포함된 120 Hz의 AC 신호를 Cds셀로 검출하여 같은 주기로 생성하였다. 이러한 수신구조는 가시광통신에서 $N{\times}1$ 광연결을 구성하는 데에 적합하다.

• Design & Manufacturing
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• 제17권2호
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• pp.55-61
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• 2023

With femtosecond (fs) laser pulse irradiation on metals, various types of nano- and micro-scale structures can be naturally induced at the surface through laser-matter interaction. Two notable structures are laser-induced periodic surface structures (LIPSSs) and cone/spike structures, which are known to significantly modify the optical and physical properties of metal surfaces. In this work, we irradiate fs laser pulses onto various types of metals, cold-rolled steel, pickled & oiled steel, Fe-18Cr-8Ni alloy, Zn-Mg-Al alloy coated steel, and pure Cu which can be useful for precise molding and imprinting processes, and adjust the morphological profiles of LIPSSs and cone/spike structures for clear structural coloration and a larger range of surface wettability control, respectively, by changing the fluence of laser and the speed of raster scan. The periods of LIPSSs on metals used in our experiments are nearly independent of laser fluence. Accordingly, the structural coloration of the surface with LIPSSs can be optimized with the morphological profile of LIPSSs, controlled only by the speed of the raster scan once the laser fluence is determined for each metal sample. However, different from LIPSSs, we demonstrate that the morphological profiles of the cone/spike structures, including their size, shape, and density, can be manipulated with both the laser fluence and the raster scan speed to increase a change in the contact angle. By injection molding and imprinting processes, it is expected that fs laser-induced surface structures on metals can be replicated to the plastic surfaces and potentially beneficial to control the optical and wetting properties of the surface of injection molded and imprinted products.

• 한국정밀공학회지
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• 제25권8호
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• pp.29-36
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• 2008

An optical rotary encoder is easy to implement for automation system applications. In particular, the output of the encoder has a digital form pulse, which is also easy to be connected to a popular digital controller. By using an incremental encoder and a counting device, it is easy to measure angular displacement, as the number of the output pulses is proportional to the rotational displacement. This method can only detect the angular placement once a pulse signal comes out of the encoder. The angular displacement detection period is strongly subject to the change of the angular displacement in case of ultimate low velocity range. They have ultimate long detection period or cannot even detect angular displacement at near zero velocity. This paper proposes an algorithm for detecting angular displacement by using a dual encoder system with two encoders of normal resolution. The angular displacement detecting algorithm is able to keep detection period moderately at near zero velocity and even detect constant angular displacement within nominal period. It is useful for motion control applications in case of changing rotational direction at which there occurs zero velocity. In this paper, various experimental results are shown for the angular displacement detection algorithm.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 학술대회지
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• pp.876-879
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• 2004

The buried fiber optic cable as a distributed intrusion sensor for detecting and locating intruders along the long perimeters is proposed. Phase changes resulting from either the pressure of the intruder on the ground immediately above the buried fiber or from seismic disturbances in the vicinity are sensed by a phase-sensitive optical time-domain reflectometer. Light pulses from a Er:fiber cw laser with a narrow, <3kHz-range, spectral width and a frequency drift of < 1 MHz/min are injected into one end of the fiber, and the backscattered light from the fiber is monitored with a photodetector. Results of preliminary studies, measurement of phase changes produced by pressure and seismic disturbances in buried fiber optic cables and simulation of ${\varphi}-OTDR$ response over long fiber paths, to establish the feasibility of the concept are described. The field experiments indicate adequate phase changes, more than 1t-rad, are produced by intruders on foot and vehicle for burial depths in the 0.2 m to 1 m range in sand, clay and fine gravel soils. The simulations predict a range of 10 km with 35 m range resolution and 30 km with 90 m range resolution. This technology could in a cost-effective manner provide enhanced perimeter security.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1997년도 춘계학술대회
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• pp.64-67
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• 1997

In the total artificial heart(TAH), a transcutaneous information transmission system(TITS) is vely important to monitor the TAH status and detect the device failure, and repair the possible problems. First of all, the communication channel(skin) and method were simulated in terms of transmittance, scattering, reflection and absorption, then the system was designed with size reduction including low power consumption and reliability compared to the previous one. The informations are transmitted through the skin(approximately 1cm in depth) by frequency modulated near infrared(NIR) pulses using 780nm laser diodes as transmitters and photodiode as receiver with high speed and high spectral sensitivity. The logic high and low frequencies are 3MHz, 1MHz respectively. The system is a bidirectional data link for more than 38.4Kbps data rate, full-duplex with a bit error rate of less than $10^{-5}$.

• Journal of Welding and Joining
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• 제34권5호
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• pp.13-18
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• 2016

Toshiba has developed a laser peening system for PWRs(pressurized water reactors) as well after the one for BWRs(boiling water reactors), and applied it for BMI(bottom-mounted instrumentation) nozzles, core deluge line nozzles and primary water inlet nozzles of Ikata Unit 1 and 2 of Shikoku Electric Power Company since 2004, which are Japanese operating PWR power plants. Laser pulses were delivered through twin optical fibers and irradiated on two portions in parallel to reduce operation time. For BMI nozzles, we developed a tiny irradiation head for small tubes and we peened the inner surface around J-groove welds after laser ultrasonic testing (LUT) as the remote inspection, and we peened the outer surface and the weld for Ikata Unit 2 supplementary. For core deluge line nozzles and primary water inlet nozzles, we peened the inner surface of the dissimilar metal welding, which is of nickel base alloy, joining a safe end and a low alloy metal nozzle. In this paper, the development and the actual application of the laser peening system for PWR power plants will be described.

• 대한전자공학회논문지
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• 제21권4호
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• pp.65-71
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• 1984

초음파 B스캔너의 경우 광대역 펄스를 사용하기 때문에 광학에서 사용되는 집속 계산식으로는 초음파 집속 시스템을 정확하게 설계할 수 없다. 본 연구에서는 초음파 다중소자에 광대역 펄스가 여기될 때 초음파의 전파모양을 정확하게 계산할 수 있늘 방법이 연구되었다. 계간된 초음차의 전파 모양을 이용하여 고해상력을 갖는 다이나믹 집속(dynamic focusing)시스템의 구동소자수, 집속치로 지연값 및 집속점 위치등을 설계하도록 하였다. 저잡음 스튀칭 특성을 갖는 다이나믹 집속 시스템을 구성하여 실험에 의해 3.5MHz선형소자로써 18cm의 깊이까지 2∼3mm의 해상도가 얻어짐을 확인하였다.

• 한국레이저가공학회지
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• 제17권4호
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• pp.7-13
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• 2014

In this work, the application of laser induced breakdown spectroscopy (LIBS) for the composition analysis of thin $Cu(In,Ga)Se_2$ (CIGS) solar cell films ($1-2{\mu}m$ thickness) is reported. For the ablation of CIGS films, femtosecond (fs) laser (wavelength = 343nm, pulse width = 500fs) and nanosecond (ns) laser (wavelength = 266nm, pulse width = 5ns) were used under atmospheric environment. The emission spectra were detected with an intensified charge coupled device (ICCD) spectrometer and multichannel CCD spectrometer for fs-LIBS and ns-LIBS, respectively. The calibration curves for fs-LIBS and ns-LIBS intensity ratios of Ga/Cu, In/Cu, and Ga/In were generated with respect to the concentration ratios measured by inductively coupled plasma optical emission spectrometry (ICP-OES).