• Journal of Korean Physical Therapy Science
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• v.10 no.1
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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.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.1
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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.

• Korean Journal of Optics and Photonics
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• v.32 no.2
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• pp.55-61
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• 2021

The lateral-mode characteristics of 850-nm GaAs/(Al,Ga)As multiple-quantum-well laser diodes and their influence on the kinks in output optical power are investigated. For the investigation, self-consistent electro-thermal-optical simulation and measurement of fabricated devices are used. From this investigation, the optimal P-cladding thickness that provides single-lateral-mode operation is determined, so that high beam quality can be achieved even at high output powers.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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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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• v.15 no.8
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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.

• Korean Journal of Optics and Photonics
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• v.7 no.3
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• pp.272-279
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• 1996

A simple transfer matrix algorithm to analyze the properties of 2 dimensional waveguides is introduced. We applied this algorithm to strained InGaAs/InGaAsP GINSCH MQW laser structures. We studied how optical confinement factor and effective refractive index, which are important in calculating the modal gain, depend on the structure parameters such as waveguide width, shape of GRIN, and number of quantum wells. Especially we suggested that the concept of effective waveguide width is very useful in understanding the GRINSCH waveguide.

• Bulletin of the Korean Chemical Society
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• v.15 no.1
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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.

• Journal of the Korean Vacuum Society
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• v.16 no.2
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• pp.141-144
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• 2007

We investigated variation of the photoreflectance(PR) signals for n-GaAs furnace and laser annealed. The samples were annealed by using ArF excimer laser(5 min, $30{\sim}50\;W$) and furnace(5 min $400{\sim}700^{\circ}C$). The PR signals(top point) measured from the ArF excimer laser annealed sample showed 1.42 eV and furnace annealed sample showed 1.43 eV. This result is ArF excimer laser annealed sample was uniform annealed surface and inter state.

• The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
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• v.29 no.4
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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.

• Journal of the Korean Vacuum Society
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• v.6 no.2
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• pp.109-113
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• 1997

PR spectra of MBE grown AlGaAs/GaAs MQW have been measured at room temperature using the He-Ne laser and the Ar laser as the pump source. We have observed various subband transition peaks and PR spectra were fitted to standard analytic line shape. Above that results, obtained us transition energy from n=1 conduction band to heavy hole(C1-H1) and to light hole(C1-L1) subband. Photoluminescence(PL) at room temperature showed main peak with a shoulder. Good agreement between PL and PR measured n=1 intersubband transition energies was confirmed that PL main peak with a shoulder is associated with the C1-H1, C1-L1 transition. Additionally, we have calculated the C1-H1 and C1-L1 intersubband energy within envelope function approximation(EFA).