• 대한물리치료과학회지
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• 제10권1호
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• pp.198-205
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• 2003

We evaluated the effect of low power GaAsAl laser on re-epithelization in full-thickness excisional wound of rat skin. Two full-thickness excisions were made on the back of the experimental animals. Low power laser applications with 10mW intensity were treated experimental animals twice a day for 7 days. On the seventh postoperative day the quantitative analysis of re-epithelization was performed using immunohistochemical staining for proliferating cell nuclear antigen (PCNA). The majority of PCNA immunoreactive cells was observed at epithelial cells in the margin of full thickness excisional wound. The low power laser treatments significantly increased the number of PCNA immunoreactive cell as compared to that of non treated animal group (p<0.01). The shape of PCNA immunoreactive cell appeared as small dark, round to ovoid structures. Most PCNA immunoreactive cells exhibited a high intensity of staining that contrasted sharply with the surrounding background. In conclusion, these findings suggest that GaAlAs laser treatments effectively enhance the epithelial wound healing by the stimulating cell proliferation. Furthermore, the majority of cell proliferation occurred in the margin of full thickness excisional wound.

• 전자공학회논문지D
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• 제35D권1호
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• pp.34-40
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• 1998

For applicating to 10-Gbit/s optical transimission systems, we have designed and fabricated a laser driver IC with extremely-high-operation-frequencies using AlGaAs/GaAs heterojunction bipolar transistors (HBTs), and have investigated its performances. Circuits design andsimulation were performed using SPICE and LIBRA. A discrete AlGaAs/GaAs HBT with the emitter area of 1.5*10 .mu.m$^{2}$, used for the circuit fabrication, exhibited cutoff frequency of 63 GHz andmaximum osciallation frquency of 50 GHZ. After fabrication of MMICs, we observed the very wide bandwidth of DC~18 GHz and the S$_{21}$ gain of 17 dB for a laser driver IC from the on-wafer measurement. Metal-packaged laser driver IC showed the excellent eye opening, the modulation currents of 32 mA, the rise/fall time of 40 ps, measured at the data rates of 10-Gbit/s.

• 한국광학회지
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• 제32권2호
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• pp.55-61
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• 2021

850 nm 대역의 발진 파장을 갖는 GaAs/AlGaAs 다중양자우물 레이저 다이오드의 lateral-mode 특성과 이 특성이 출력 광파워 kink에 미치는 영향을 조사하였다. 이를 위해 전기적-열적-광학적 시뮬레이션을 self-consistent하게 수행하고, 제작된 레이저 다이오드 소자들을 측정하였다. 연구 결과를 바탕으로 높은 출력 파워에서도 single lateral-mode를 유지해서 좋은 beam quality를 유지할 수 있는 최적의 P-cladding 두께를 결정하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 추계학술대회 논문집 Vol.18
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• pp.78-79
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• 2005

We report on optically excited terahertz (THz) omission from low-temperature (LT) grown GaAs. We have used 70 fs titanium-sapphire laser pulses with wavelengths at 800 nm to generate THz radiation pulses. The LT-GaAs layers are grown on semi-insulating GaAs substrates with GaAs buffer layer by molecular beam epitaxy (MBE). The THz emission from the LT-GaAs surface is strong and does not show any significant variation in the strength of the THz emission over several different angles between the polarization of the excitation laser pulse and the crystallographic orientation of the LT-GaAs.

• Bulletin of the Korean Chemical Society
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• 제15권8호
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• pp.663-669
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• 1994

Decay kinetics of Ga(5s), Ga(5p) and Ga(4d) atoms in Ar were studied by laser induced fluorescence technique. Theground state gallium atoms in the gas phase were generated by pulsed dc discharge of trimethyl gallium and argon mixtures. Both pulsed discharge and YAG-DYE laser system were controlled by a dual channel pulse generator and the delay time between the end of discharge and laser pulses was set 3.0-6.0 ms. The Ga(5s) and Ga(4d) atoms were generated by single photon excitation from the ground state Ga atoms and radiative lifetimes as well as the total quenching rate constants in Ar were obtained from the pressure dependence of the fluorescence decay rates. The Ga(5p) atoms were populated by a two-photon excitation method and the cascade fluorescence from Ga(5s) atoms were analyzed to extract quenching rate constant of Ga(5p) atoms by Ar in addition to radiative lifetimes of Ga(5p) state. The magnitudes of the quenching rate constants by Ar for the low-lying excited states of Ga atoms are 1.6-3$ {\times}10^{-11}cm^3$ molecul$e^{-1}s^{-1}$, which are much larger than those for alkali, alkaline earth and Group 12 metals. Based on the measured rate constants, kinetic simulations were done to assign state-to-state rate constants.

• 한국광학회지
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• 제7권3호
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• pp.272-279
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• 1996

이차원 파동길잡이의 성질을 분석할 수 있는 간단한 넘김행렬 풀이법을 개발하였다. 이 풀이법을 변형된 InGaAs/ImGaAsP GRINSCH MQW 레이저 구조에 적용하여 방식 이득을 계산하는데 필요한 광학가둠 인자, 유효꺽임율 등이 파동길잡이 너비, GRIN의 모양, 양자우물의 갯수 등의 구조 변수에 어떻게 의존하는지 살펴보았다. 특히 GRIN 파동길잡이를 이해하는데 유효 파동길잡이 너비의 개념이 유용함을 보였다.

• Bulletin of the Korean Chemical Society
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• 제15권1호
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• pp.28-33
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• 1994

The laser-assisted chemical vapor deposition (LCVD) is described, by which the growth of single-phase GaN epitaxy is achieved at lower temperatures. Trimethylgallium (TMG) and ammonia are used as source gases to deposit the epitaxial films of GaN under the irradiation of ArF excimer laser (193 nm). The as-grown deposits are obtained on c-face sapphire surface near 700$^{\circ}$C, which is substantially reduced, relative to the temperatures in conventional thermolytic processes. To overcome the lattice mismatch between c-face sapphire and GaN ad-layer, aluminum nitride(AlN) is predeposited as buffer layer prior to the deposition of GaN. The gas phase interaction is monitored by means of quadrupole mass analyzer (QMA). The stoichiometric deposition is ascertained by X-ray photoelectron spectroscopy (XPS). The GaN deposits thus obtained are characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM) and van der Pauw method.

• 한국진공학회지
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• 제16권2호
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• pp.141-144
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• 2007

n-GaAs의 시료를 furnace annealing 처리와 laser annealing 처리를 한 후, PR 방법으로 비교 조사하였다. 시료는 Furnace annealing을 5 분간 $400{\sim}800^{\circ}C$에서 처리한 시료와 ArF excimer laser($30{\sim}50\;W$)로 5 분간 Laser annealing 처리 한 시료로 준비하였다. Furnace로 annealing을 한 경우에 주 신호(정점)는 1.43 eV에서 관측되었는데 비해 laser로 annealing 한 샘플은 1.42 eV로 0.01 eV가 더 작게 관측되었다. 이는 laser annealing이 furnace annealing 보다 표면과 내면에서 일어나는 열처리 효과가 더 고르게 일어나가 때문이다.

• 한방안이비인후피부과학회지
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• 제29권4호
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• pp.14-23
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• 2016

Objectives : One of major complications of diabetes, diabetic ulcer is also one of the main reasons for amputation, and the prevalence rate is 4-10%. Laser therapy is widely used for leg ulcer and diabetic ulcer, and it is known to improve wound epithelialization, cellular content, and collagen deposition. The purpose of this study is to investigate the properties of the laser and the spectrum of laser instruments for diabetic ulcer. Methods : We performed literature search using the PubMed, Cochrane, CINAHL and Web of science for the data in English. In addition, other databases were checked for different languages such as OASIS and NDSL for the literature in Korean, CNKI in Chinese, and CiNii and J-STAGE written in Japanese. We excluded all review article and experimental studies, and only clinical studies using laser or light emitting diode (LED) for diabetic ulcer were selected. Results : A total twenty papers were selected. Different light sources were used as follows: LED, HeNe, InGaAlP, GaAlAs, GaAs, CO2, and KTP. The number of LED studies was 9, and HeNe laser was 7, and InGaAlP and GaAlAs laser was 2, GaAs, CO2, and KTP laser was 1 for each. Various energy density of the clinical study were reported. Conclusions : It is suggested that to select appropriate laser type and give the adequate output power to treat diabetic ulcer. Further evaluation and research for the condition of laser therapy to treat diabetic ulcers are warranted.

• 한국진공학회지
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• 제6권2호
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• pp.109-113
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• 1997

MBE로 성장한 AlGaAs/GaAs multiple-quantum well(MQW)에 대하여 pump source를 He-Ne laser와 Ar laser를 사용하여 상온에서 PR(photoreflectance)측정을 수행한 결과 여러 subband transition peak을 관찰하였다. PR결과를 standard analytic line shape으 로 fitting하여n=1의 conduction band와 heavy hole 그리고 light hole transition peak인 Cl-Hl, Cl-Ll에 대한 energy값들을 얻었다. 또한 상온에서의 PL(photoluminescence)측정에 서 Cl-Hl, Cl-Ll과 관련된 main peak와 shoulder를 관찰하였다. 이 값은 PR측정값과 잘 일 치함으로써 PL에서의 main peak와 should가 Cl-Hl, Cl-Ll과 관련된 peak임을 확인할 수 있 었다. 또한 envelope function approximation(EFA)을 이용하여 구한 이론값과 PR과 PL에서 측정된 실험값들을 비교하였다.