• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.10
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• pp.43-50
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• 1995

A laser diode(LD) structure consisting of a single 150$\AA$ $Al_{0.07}$Ga$_{0.93}$As quantum well active region operating at ${\lambda}$=809nm, cladded with an AlGaAs graded-index separate confinement heterostructure, has bes been grown by MOCVD. Temperature coefficient of wavelength is approximately 0.2nm $^{\circ}C$ for the diode. The active aperture consists of five emitters separated from each other by means of SiO$_{2}$ deposition and stripe formation, which creates insulating regions that channel the current to 100-$\mu$m-wide stripes placed on 450-$\mu$m centers. From a typical uncoated LD, the output power of 0.8W has been obtained at a 1$\mu$s, 1kHz pulsed current level of 2.0$\AA$, which results in about 64% external quantum efficiency. The threshold current density is 736A/cm$^{2}$ for the case of 500$\mu$m cavity length LD's. The measure of an internal quantum efficiency was 75.8% and the internal loss 4.83$cm^{-1}$ . Finally, 3.1W output power has been obtained at a 1$\mu$s, 1kHz pulsed current level of 9A from the 500$\mu$m-aperture LD array with 460-$\mu$m- cavity length.

• Korean Journal of Optics and Photonics
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• v.13 no.3
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• pp.235-239
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• 2002

A novel ultra-narrow linewidth DFB laser in the extended FBG ring cavity having kHz linewidth is presented. The method of linewidth compression was realized by introducing an extended fiber ring cavity into the cavity between the external FBG and the Bragg grating inside a DFB laser diode. Optimum optical feedback control was achieved by using an optical circulator and a variable optical attenuator to prevent mode hopping induced by spatial hole burning. To prove the validity of the proposed scheme, a self-heterodyne measurement set-up with fiber delay line of 63 km was utilized for the ultra-narrow linewidth measurement. A 3 dB linewidth of less than 3 kHz was demonstrated, which is resolution limited performance. This linewidth is equivalent to 3 dB linewidth of 2$\times$10$^{-8}$ nm.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.3
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• pp.50-56
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• 2015

In this study, AISI M2 powder was selected primarily through various pieces of literature in order to improve the hardness and wear resistance. Among the laser metal deposition parameters, laser power was studied to improve the deposition efficiency in the laser metal deposition using a diode-pumped disk laser. An SKD61 hot work steel plate and AISI M2 powder were used as a substrate and powder for laser metal deposition, respectively. Experiments for the laser metal deposition were carried out by changing the laser power and track layer. The quality of the track surface and cross-section after applying the single-layer method was better than that obtained from applying the multi-layer method. As the laser power increased, the track thickness was increased, and the surface roughness deviation was decreased. In laser power condition of 1.6kW, the maximum hardness of the deposition track was 790Hv. This value was 40% better than the hardness of the SKD61 after heat treatment.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.58.1-58.1
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• 2010

In solar cell module manufacturing, single solar cells has to be joined electrically to strings. Copper stripes coated with tin-silver-copper alloy are joined on screen printed silver of solar cells which is called busbar. The bus bar collects the electrons generated in solar cell and it is connected to the next cell in the conventional module manufacturing by a metal stringer using conventional hot air or infrared lamp soldering systems. For thin solar cells, both soldering methods have disadvantages, which heats up the whole cell to high temperatures. Because of the different thermal expansion coefficient, mechanical stresses are induced in the solar cell. Recently, the trend of solar cell is toward thinner thickness below 180um and thus the risk of breakage of solar cells is increasing. This has led to the demand for new joining processes with high productivity and reduced error rates. In our project, we have developed a new method to solder solar cells with a laser heating source. The soldering process using diode laser with wavelength of 980nm was examined. The diode laser used has a maximum power of 60W and a scanner system is used to solder dimension of 6" solar cell and the beam travel speed is optimized. For clamping copper stripe to solar cell, zirconia(ZrO)coated iron pin-spring system is used to clamp both joining parts during a scanner system is traveled. The hot plate temperature that solar cell is positioned during lasersoldering process is optimized. Also, conventional solder joints after $180^{\circ}C$ peel tests are compared to the laser soldering methods. Microstructures in welded zone shows that the diffusion zone between solar cell and metal stripes is better formed than inIR soldering method. It is analyzed that the laser solder joints show no damages to the silicon wafer and no cracks beneath the contact. Peel strength between 4N and 5N are measured, with much shorter joining time than IR solder joints and it is shown that the use of laser soldering reduced the degree of bending of solar cell much less than IR soldering.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.1
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• pp.49-54
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• 1997

We proved the feasibiltiy of a parallel optical interconnection technique using single GRIN (graded-index) rod lens as an intermediate coupling device, which increases the working distance and makes packaging easy. The proposed technique shows relatively less dependency on misalignments. In this paper, for convensience of experiments, we applied this method to 4-channel coupling between two fiber arrays, and compared it with butt-coupling and the method of using ball lens. The comparison shows the feasibility of adopting the proposed method to the parallel interconnection between a laser diode array and an optical fiber array.

• 한국정보통신설비학회:학술대회논문집
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• 2003.08a
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• pp.93-95
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• 2003

We have designed and fabricated a micromirror array using single crystalline silicon (SCS) for data communication applications. The mirror array has $16{\times}16$ micromirrors and each mirror has $120{\mu}m{\times}100{\mu}m$ reflective surface. Electrostatic force was adopted as a driving mechanism. The spring dimensions were determined using relationship between spring dimensions and driving voltage. The designed tilting angle was $9.6^{\circ}$, and measured tilting angle according to applied voltages were experimented. The response time was measured using He-Ne laser and position sensitive diode (PSD), and lifetime was checked for reliability proof.

• 연구논문집
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• s.30
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• pp.43-56
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• 2000

N-IR spectroscopy technology is very useful. And, the technology has wide application range. In the range, we know that single beam type silica analyzer has some handicap. So we were studied Splitted beam type silica analyzer. This dissertation have been discuss about system structure, system fundamentals and performance test. At the test, we were study in the spectral interference of NH3. We know that existing system had some problem. It is structural frailties of single beam type. Therefore we were study for Splitted beam type structure. And we obtain a good result. We have $\pm$5% accuracy and 0.5 ppb level measuring range. But, we have a question. It is ppt level measuring technology by the laser beam spectroscopy.

• Journal of the Korea Institute of Military Science and Technology
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• v.20 no.6
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• pp.733-742
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• 2017

LADARs are used for important sensors in various applications, for example, terrain information sensors in self driving cars, safety sensors for factory automation, and 3D map constructions. This study develop important component technologies to improve the performance of a LADAR system under development in Korea. The component technologies include diode temperature regulation, reducing distance error in outdoor environment, and signal processing technique for better detection of distant objects. This paper explains the suggested component technologies and experimental results of the developed LADAR system. Also, the developed system is operated and tested an a single axis driving platform to acquire 3D information from 2D LADAR.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.1
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• pp.44-48
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• 2002

In this paper, we demonstrated the simultaneous measurment of triple parameters such as strain, temperature, and vibration using single FBG/EFPI hybrid sensor. The FBG/EFPI sensor system for the strain and temperature measurement and the EFPI sensor system for the the vibration measurement were combined by a wavelength division multiplexer. The optical source of FBG/ EFPI sensor system is a wavelength-swept fiber laser(WSFL) and that of an EFPI sensor system is a laser diode. We performed the simultaneous measurement of thermal strain, temperature, and vibration of a aluminum beam placed in a thermal chamber and validated the efficiency of the constructed measurment system.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1671-1673
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• 2003

Faraday효과를 기본으로 하는 광CT(Optical Current Transformer)는 기존의 CT의 결점을 개선하여 경제적 효과의 증대, 신호제어 시스템의 신속성향상, Digital 계전시스템의 호환성에 크게 기여한다는 점 등 많은 면에서 장점을 가지고 있다. 본 연구에서는 광섬유센서 기술을 응용하고, Faraday 효과의 편광면 회전량을 수광부에서 김출하여 대전류 측정을 위한 광 CT의 동작특성에 대한 실험을 하고자 한다. 실험에 사용찬 광원은 633[nm] He-Ne Laser와 1310[nm] Laser Diode 두 가지로 동일한 시스템으로 구성하여 비교한다. 센싱부의 광섬유는 길이 10[m]의 633[nm] 1310[nm]용 single-mode bare fiber를 전류가 흐르는 케이블에 감아 센싱부를 구성하고, 전류변화에 따른 두 출력값을 측정, 비교하고자 한다.