• Korean Journal of Materials Research
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• v.31 no.11
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• pp.601-607
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• 2021

Laser cladding a surface treatment process that grants superior characteristics such as toughness, hardness, and corrosion resistance to the surface, and rebuilds cracked molds; as such, it can be a strong tool to prolong service life of mold steel. Furthermore, compared with the other similar coating processes - thermal spray, etc., laser cladding provides superior bonding strength and precision coating on a local area. In this study, surface characteristics are studied after laser cladding of low carbon steel using 18%Cr-2.5%Ni-Fe powder (Rockit404), known for its high hardness and excellent corrosion resistance. A diode laser with wavelength of 900-1070 nm is adopted as laser source under argon atmosphere; electrical power for the laser cladding process is 5, 6, and 10 kW. Fundamental surface characteristics such as crossectional microstructure and hardness profile are observed and measured, and special evaluation, such as a soldering test with molten ALDC12 alloy, is conducted to investigate the corrosion resistance characteristics. As a result of the die-soldering test by immersion of low carbon alloy steel in ALDC12 molten metal, the clad layer's soldering thickness decreases.

• Journal of the Korean Institute of Telematics and Electronics
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• v.25 no.11
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• pp.1367-1372
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• 1988

In this paper, we have optimized the computation of the CSP - LOC (Channel Substrate Planar-Large Optical Cavity) structure to design the gith power (Ga, Al) As/GaAs CSP-LOC laser diode. The parameters of the device on the bases of experimental datas include the effects of the various layer thickness, material absorption coefficients, stripe width and so forth. At active layer ($d_2$)=0.08 um with optical layer ($d_3$)=0.5 um and $d_2$ = 0.1 um with $d_3$ = 0.4 um, we find the narrower beam divergence and stable high power in the lowest-order mode without the phenomenon of spatial hole burning. The results of theoretical computation show good agreement with experimental measurements made on LPE grown CSP-LOC. Finally, we developed an practical program and the program is applicable to the CSP-LOC lasers with any materials.

• Journal of Chest Surgery
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• v.40 no.2 s.271
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• pp.97-102
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• 2007

Background: Endovenous laser treatment has recently been introduced as a less invasive technique, with many good results reported, A 980-nm diode laser was used on the great saphenous vein (GSV) occlusions in patients with varicose veins, due to GSV reflux, and the therapeutic effects analyzed. Material and Method: Between September 2003 and February 2006, 238 patients (332 cases) with GSV reflux underwent endovenous laser treatment with a 980-nm diode laser. Operative procedures were simultaneous endovenous laser treatment and ambulatory phlebectomy. The preoperative clinical findings, postoperative complications and postoperative duplex US follow up results at 1 and 3 months were reviewed. Result: Postoperative complications were ecchymosis in almost cases, paresthesia 68 cases (20.5%) and skin burn in 3 cases (0.9%). Follow up duplex US revealed 26 and 10 cases at 1 and 3 months of GSV reflux or partial recanalization, with therapeutic success rates of 91.3 and 87.9%, respectively. Conclusion: The treatment of GSV occlusion with an endovenous laser is less invasive than traditional GSV stripping, but relatively high recanalization was experienced, possibly due to inadequate laser power, laser fiber pullback speed or an extremely dilated GSV. However, continuous attempts will be required to reduce the recanalization after the procedure, with accurate follow up using duplex US.

• 전기의세계
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• v.11
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• pp.14-17
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• 1963

정확하게 control된 pulse의 용도는 과학과 공업이 발달될수록 날로 많아져 가고 있는데 그의 일부는 대전력을 취급하는 경우로서, Radar에 대한 응용을 들 수 있다. 한편, 요지음 gallium-arsenide등 반도체 diode를 사용해서 Laser action을 일으킬 수 있다는것이 발견되어 G.E. 및 IBM등에서 개발되고 있다. 이 경우에, continuous emission도 가능하지만 흔히, intermittent operation을 시켜야 할 때가 많기 때문에 timed pulse source가 필요하게 된다. 또 한편, spot welding의 경우에도 이러한 pulse source가 필요하게 된다. 이들을 크게 나누어 source를 AC로 할 경우와 DC로 할 경우가 있는데, 전자의 경우는 thyratron을 사용할 경우가 많게 될 것이다. DC의 경우나 AC의 경우에나 잘 shape되고 time된 pulse source를 만들어 놓으면 진공관이나 thyratron이나 같은 모양으로 drive할 수 (thyratron의 경우는 trigger)있을 것이기 때문에, 이러한 pulse source를 만들 필요가 있게 된다.

• Proceedings of the Optical Society of Korea Conference
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• 2003.02a
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• pp.92-93
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• 2003

간섭계의 광원으로 현재 레이저를 주로 사용하고 있다. 이러한 간섭계용 레이저의 조건은 선폭(linewidth) 이 좁아야 하고, 중심 주파수가 안정화 되어야 한다. 특히 거리용 간섭계의 경우, 주파수 안정화되어 있는 레이저가 사용되어 측정 불확도를 낮춘다. 그러나 점차 다축을 측정하기 위한, 또는 보다 넓은 영역을 측정하기 위해서는 보다 높은 출력의 레이저를 요하고 있다. 그러나 현재의 간섭계용 레이저는 헬륨네온 레이저로서 단일 모드 기준으로 2 mW 이하의 출력을 보이고 있어서 응용 면에 있어서 제약을 받는다. (중략)

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.8
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• pp.1041-1047
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• 2011

In this study, two types of die material cast iron was treated for surface hardening by using high power diode laser to improve mechanical properties of die which is using as essential production technology in the parts manufacturing in virtually all the infrastructure industries now. First of all, the heat treatment characteristics of FCD550 material which is spheroidal graphite cast iron, and through the heat treatment of HCI350 material which is flake graphite cast iron, the heat treatment characteristics of the two materials were compared. The hardness of hardened zone increased over 3 times over base material for both specimens, but as for required heat input, HCI350 was higher than FCD550 material depending on the heat conductivity of the materials by the content amount and shape of graphite contained in the material.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.3
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• pp.109-113
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• 2004

In this paper, we took the basic experiment in order to explore the optical CT(optical current transformer) for measuring high current in a superhigh voltage condition. It is based on the faraday effect that changes the polarization characteristic of optical signals by the magnetic field. We used 1310[nm] laser diode for a light source and comprised a sensing part with the optional fiber of 5[m], 10[m], 20[m] length each. The range of current was from 400[A] to 1300[A]. We observed the characteristic of output that changes according to the length of the optical fiber composing the sensing part. The optical fiber of 5[m] length used for the sensing part had -11.1% of the maximum ratio of error and 10[m] and 20[m] length had -3.5% and 1.7% each. This means that the power and linearity of output increase in proportion to the length of optical fiber and applied current in the same experimental condition.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.131-131
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• 2010

The power of semiconductor laser diodes has been limited primarily by the heating effects which occur at high optical intensities. The actual limiting event can take one of a number of forms such as. catastrophic optical damage or filamentation. A general approach to this problem is to design a heterostructure which creates a high powered output while maintaining low internal optical intensities. A graded index separate confinement heterostructure (GRIN-SCH) is one such structure that accomplishes the above task. Here, the active region is sandwiched between graded index layers where the index of refraction increases nearer to the active layer. This structure has been shown to yield a high efficiency due to the confinement of both the optical power and carriers, thereby reducing the optical intensity required to achieve higher powers. The optical confinement also reinforces the optical beam quality against high power effects. Quantum dots have long been a desirable option for laser diodes due to the enhanced optical properties associated with the zeroth dimensionality. In our work, we use PICS3D software created by Crosslight Software Inc. to simulate the performance of In0.67A10.33As/A10.2Ga0.8AsquantumdotsusedwithaGRIN-SCH. The simulation tools are used to optimize the GRIN-SCH structure for high efficiency and optical beam quality.

• Journal of the Korean Society for Heat Treatment
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• v.24 no.4
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• pp.203-208
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• 2011

Recently, from general machine parts and automobile parts using carbon steel to a mold, there has been efforts for improving durability and attrition resistance of these parts. Especially, heat treatment with laser which works fast and automatically can be used for the mass production with high quality. Moreover, local heat treatment can be used to handle with complex and precise parts. Accordingly, we analyzed hardening characteristics of carbon steel using the finite element method and compare the experimental results to have more reliability. We also proved the cause of thermal deformation with temperature and stress distribution by heat treatment. After these analysis and experimental, we found that each maximum hardness of the two tests was 728 Hv and 700 Hv, on condition of $1050^{\circ}C$ heating temperature, and 2 mm/sec laser speed. We also found that difference of surface stress-distribution was occurred, and this makes deformation mode up after heat treatment.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.3
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• pp.47-55
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• 1996

An optical transmitter, which is a key component of the optical transmission system, converts the electrical signal to optical signal and consists of a high-speed current-pulse driver for laser diode and low-speed feedback loops that stabilize optical power against aging, power supply voltage fluctuations, and ambient temperature changes. In this paper, the power-stabilizing part, which forms the bulk of the optical transmitter circuitry was designed in integrted circuits. Operational amplifiers and reference voltage generation circuits, which were identified as key building blocks for the power-stabilizing feedback loops, were designed and were subsequently verified through HSPICE simulations. The designed operational amplifier consists of a two-stage folded cascode amplifier and class AB output stage, whereas the reference voltage is obtained by bandgap reference circuits. Finally the power-stabilizing circuitry was laid out based on 3\mu$m CMOS design rules for fabrication.