• The Journal of Korean Physical Therapy
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• v.14 no.4
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• pp.87-94
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• 2002

Low intensity laser irradiation is potential physical agent that triggers the muscle regeneration by previous study. In muscle regeneration, a number of growth factors also promotes that is triggered in response to muscle damage. The transforming growth factor(TGF)-$\beta$ is involved in the activation of cell proliferation and the inhibition of cell differentiation in muscle regeneration. This is secreted not only autocrine system but also paracrine and endocrine. Therefore, We investigated that effects of Gallium aluminum arsenide(GaAlAs) diode laser for the expression of TGF-$\beta$ on lumbar spinal cord after extensor digitorum muscle crush injury. After laser irradiation, the immunoreactivity of TGF-$\beta$ was increased bilaterally in gray mater of spinal cord. Especially, in 1 day, experimental group was highed than control, and in 3 day, lateral motor nucleus were storong immunoreactivy of TGF-$\beta$. Also, in 1 and 2 day, TGF-$\beta$ was showed in white mater as well as gray mater, but in 3 day, only showed in gray mater. These data may suggests to the establishment of laser irradiation on spinal cord for skeletal muscle injury.

• Korean Journal of Optics and Photonics
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• v.5 no.2
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• pp.278-285
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• 1994

We investigated the spectral characteristics for temperature and driving current change in visible laser diode. As a result of spectrum analysis, the ratio of frequency change for temperature and driving current change were about $33 GHz/^{\circ}C$, 6.6 GHz/mA in the region which was not mode hopping range. Compared to the sharp mode hopping in the near IR single mode AlGaAs lasers, the visible laser diode showed relatively broad multimode operation in the mode hopping region. We performed the experiment of injection-locking characteristics analysis for visible laser diode. Locking half bandwidth(LHBW) was measured 0~5.0 GHz for $0~25\muW$ input power and it was dependent on the input power. Also, LHBW for polarization angle was dependent on the difference of polarization angle between master laser and slave laser. The phase change of injection-locked output beam of the slave laser diode as a function of the drive current was measured in the interferometer which was composed of master laser and slave laser. The ratio of phase change with the slope of 5.0~1.3 rad/mA was obtained within injection-locking range for the change of $2~25\muW$ input power. power.

• The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
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• v.30 no.4
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• pp.62-74
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• 2017

Objectives : The purpose of this study is to investigate the effect of laser therapy for diabetic ulcer by using methods of systematic review. Methods : In this review, PubMed, Cochrane library, Web of Science, CNKI, CiNii, J-STAGE, NDSL and OASIS were used as the search engines. The search period is from the start date of the search engine to October 3, 2016. Randomized controlled trials(RCTs) using laser therapy for diabetic ulcer were searched and extracted by two independent researchers. Risk of bias(RoB) of Cochrane was used to assess methodological quality of studies. Results : Finally, five RCTs were selected. The follow-up period ranged from 15 days to 20 weeks. InGaAlP laser, GaAlAs laser and light emitting diode(LED) were used to treat diabetic ulcer. The clinical trials used sham laser irradiation or standard treatment as control in comparison to laser therapy. The endpoints included ulcer size, rate of healing and time to healing with follow-up period. The RCTs demonstrated therapeutic outcomes with no adverse effect. Most items of RoB were unclear and methodological quality was low. Conclusions : Our analysis suggests that laser therapy has therapeutic effects for diabetic ulcer. However, more systematic and stringent clinical trials will be required.

• Journal of the Korean institute of surface engineering
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• v.23 no.4
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• pp.197-207
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• 1990

Atomic layer epitaxy is a relatively new epitaxial pprocess chracterized by the alternate and separate exposure of a susbstrate surface to the reactants contaning the constituent element of a compound semicoductror. The ideal ALE is expected to provide sevral advantageous as petcts for growing complicated heterostrutures such as relativly easy controls of the layer thinkness down to a monolayer and in forming abrupt heterointerfaces though monolayer self-saturatio of the growth. In addition, since ALE is stongly dependent on the surface reaction, the growth can also be controlled by photo-excitation which provides activation can be energies for each step of the reaction paths. The local growth acceleration by photo-excitation can be exploited for growing several device strures on the same wafer, which provides another important practical advantage. The ALE growth of GaAs has advanced to the point the laser opertion has been achieved from AlGs/GaAs quantun well structures where thee active layers were grown by thermal and Ar-laser assisted ALE. The status of the ALE growth of GaAs and other III-V compounds will be reviewed with respect to the growth saturation behavior and the electrical properties of the grown crystals.

• Journal of Powder Materials
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• v.29 no.2
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• pp.99-109
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• 2022

Powder flowability is critical in additive manufacturing processes, especially for laser powder bed fusion. Many powder features, such as powder size distribution, particle shape, surface roughness, and chemical composition, simultaneously affect the flow properties of a powder; however, the individual effect of each factor on powder flowability has not been comprehensively evaluated. In this study, the impact of particle shape (sphericity) on the rheological properties of Ti-6Al-4V powder is quantified using an FT4 powder rheometer. Dynamic image analysis is conducted on plasma-atomized (PA) and gas-atomized (GA) powders to evaluate their particle sphericity. PA and GA powders exhibit negligible differences in compressibility and permeability tests, but GA powder shows more cohesive behavior, especially in a dynamic state, because lower particle sphericity facilitates interaction between particles during the powder flow. These results provide guidelines for the manufacturing of advanced metal powders with excellent powder flowability for laser powder bed fusion.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.3
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• pp.52-59
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• 1997

Design and performance of principal four ICs for the 10-Gb/s optical communication system are presented. AlGaAs/GaAs HBTs are basic devices to implement a laser diode driver, apre-amplifier, and a limiting amplifier, and GaInP/GaAs HBTs are used for an AGC amplifier. We fbricated 11.5-GHz LD driver, a pre-amplifier, and a limiting amplifier, an dGaInP/GaAs HBTs are used for an AGC amplifier. We fabricated LD deriver, 10.5 GHz pre amplifier, 7.2 GHz AGC amplifier, and 10.3 GHz limiting amplifier, optimized circuit design and the stabilized MMIC fabrication process.

• Journal of Convergence for Information Technology
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• v.10 no.6
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• pp.28-34
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• 2020

A structure in which GaAs and AlGaAs epilayers are formed with a metal organic chemical vapor deposition equipment on a GaAs wafer similar to the structure of making a vertical cavity surface emitting laser is used. Photonic Quantum Ring (PQR) devices that are naturally generated by 3D resonance are manufactured by chemically assisted ion beam etching technology, which is a dry etching method. A new technology that can be fabricated has been studied, and as a result, the possibility of wet etching of a solution containing phosphoric acid, hydrogen peroxide and methanol was investigated, and the device fabrication by applying this method are also discussed. In addition, the spectrum of the fabricated optical device was measured, and the results were theoretically analyzed and compared with the wavelength value obtained by the measurement. It is expected that the PQR device will be able to model cells in a three-dimensional shape or be applied to the display field.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.342-343
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• 2013

AlSb is a promising material for optical devices, particularly for high-frequency and nonlinear-optical applications. And AlSb offers significant potential for devices such as quantum-well lasers, laser diodes, and heterojunction bipolar transistors. In this work we study molecular beam epitaxy (MBE) growth of an unstrained AISb film on a GaAs substrate and identify the real-time monitoring capabilities of in situ spectroscopic ellipsometry (SE). The samples were fabricated on semi-insulating (0 0 1) GaAs substrates using MBE system. A rotating sample stage ensured uniform film growth. The substrate was first heated to $620^{\circ}C$ under As2 to remove surface oxides. A GaAs buffer layer approximately 200 nm- thick was then grown at $580^{\circ}C$. During the temperature changing process from $580^{\circ}C$ to $530^{\circ}C$, As2 flux is maintained with the shutter for Ga being closed and the reflection high-energy electron diffraction (RHEED) pattern remaining at ($2{\times}4$). Upon reaching the preset temperature of $530^{\circ}C$, As shutter was promptly closed with Sb shutter open, resulting in the change of RHEED pattern from ($2{\times}4$) to ($1{\times}3$). This was followed by the growth of AlSb while using a rotating-compensator SE with a charge-coupled-device (CCD) detector to obtain real-time SE spectra from 0.74 to 6.48 eV. Fig. 1 shows the real time measured SE spectra of AlSb on GaAs in growth process. In the Fig. 1 (a), a change of ellipsometric parameter ${\Delta}$ is observed. The ${\Delta}$ is the parameter which contains thickness information of the sample, and it changes in a periodic from 0 to 180o with growth. The significant change of ${\Delta}$ at~0.4 min means that the growth of AlSb on GaAs has been started. Fig. 1b shows the changes of dielectric function with time over the range 0.74~6.48 eV. These changes mean phase transition from pseudodielectric function of GaAs to AlSb at~0.44 min. Fig. 2 shows the observed RHEED patterns in the growth process. The observed RHEED pattern of GaAs is ($2{\times}4$), and the pattern changes into ($1{\times}3$) with starting the growth of AlSb. This means that the RHEED pattern is in agreement with the result of SE measurements. These data show the importance and sensitivity of SE for real-time monitoring for materials growth by MBE. We performed the real-time monitoring of AlSb growth by using SE measurements, and it is good agreement with the results of RHEED pattern. This fact proves the importance and the sensitivity of SE technique for the real-time monitoring of film growth by using ellipsometry. We believe that these results will be useful in a number of contexts including more accurate optical properties for high speed device engineering.

• Journal of the Korean Vacuum Society
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• v.15 no.2
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• pp.201-208
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• 2006

Optical characteristics of InGaAs quantum dot (QD) laser structures with an Al native oxide (AlOx) layer as a current-blocking layer were studied by means of photoluminescence (PL), PL excitation, and spatially-resolved micro-PL techniques. The InGaAs QD samples were first grown by molecular-beam epitaxy (MBE), and then prepared by wet oxidation and thermal annealing techniques. For the InGaAs QD structures treated by the wet oxidation and thermal annealing processes, a broad PL emission due to the intermixing effect of the AlOx layer was observed at PL emission energy higher than that of the non-intermixed region. We observed a dominant InGaAs QD emission at about 1.1 eV in the non-oxide AlAs region, while InGaAs QD-related emissions at about 1.16 eV and $1.18{\sim}1.20eV$ were observed for the AlOx and the SiNx regions, respectively. We conclude that the intermixing effect of the InGaAs QD region under an AlOx layer is stronger than that of the InGaAs QD region under a non-oxided AlAs layer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.353-356
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• 1996

Ultra-high-speed analog and digital ICs (integrated circuits) fur 10Gbit/sec optical communication systems have been designed, fabricated and analyzed in this research. These circuits, which are laser diode (LD) driver, pre-amplifier, automatic gain controlled (AGC) amplifier, limiting amplifier and decision circuit, have been implemented with AIGaAs/GaAs heterojunction bipolar transistors (HBTs). The optimized AIGaAs/GaAs HBTs for the 10Gbps circuits in this work showed the cutoff and maximum oscillation frequencies of 65㎓ and 53㎓, respectively. It is demonstrated in this paper that the 10Gbps optical communication system can be realized with the ICs designed and fabricated using AlGaAs/GaAs HBTs.