• Journal of Oral Medicine and Pain
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• v.10 no.1
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• pp.91-104
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• 1985

In order to study the effects of the low power density laser (AsGa) on the wound healing of tongue and skin, thirty two healthy rats were anesthetized with pentothal. The tongue wound, approximately 1 mm in depth and 2mm in diameter, was created on the anterior of the tongue and the skin wound, approximately, 2mm in depth and 6-8mm in diameter, was created on the back of rat with the tip of small rongeur forcep. Wounds of experimental groups were irradiated with AsGa laser (Stomalaser, SEDATELEC Co., France) every other day by ninth day. The areas of wounds were measured at 1, 3, 5, 7, 9 days after wounding and the specimens were sectioned, stained, and observed with light microscope. The results were as follows : 1. In the AsGa laser irradiated wound of tongue, the epithelial and fibroblastic regeneration were accelerated when compared with controls. 2. In the AsGa laser irradiated wound of skin, the epithelial and fibroblastic regeneration were accelerated when compared with controls. 3. When the wound areas were compared, there was a significant difference between control group and experimental group (P < 0.01: 2-Way NOVA).

• Applied Science and Convergence Technology
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• v.26 no.4
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• pp.79-85
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• 2017

The crack-free AlGaN template has been successfully grown by using selective area growth with triangular GaN facet. The triangular GaN stripe structure was obtained by vertical growth rate enhanced mode with low growth temperature of $950^{\circ}C$ and high growth pressure of 500 torr. The lateral growth rate enhanced mode of AlGaN for crack-free and flat surface was also investigated. Low pressure of 30 torr and high V/III ratio of 4400 were favorable for lateral growth of AlGaN. It was confirmed that the $4{\mu}m$ -thick $Al_{0.2}Ga_{0.8}N$ was crack-free over entire 2-inch wafer. The dislocation density of $Al_{0.2}Ga_{0.8}N$ was as low as ${\sim}7.6{\times}10^8/cm^2$ measured by cathodoluminescence. Based on the high quality AlGaN with low dislocation density, the ultraviolet laser diode epitaxy with cladding, waveguide and GaN/AlGaN multiple quantum well (MQW) was grown by metalorganic chemical vapor deposition. The stimulated emission at 349 nm with full width at half maximum of 1.8 nm from the MQW was observed through optical pumping experiment with 193 nm KrF laser. We also have fabricated the deep ridge type ultraviolet laser diode (UV-LD) with $5{\mu}m-wide$ and $700{\mu}m-long$ cavity for electrical properties. The turn on voltage was below 5 V and the resistance was ${\sim}55{\Omega}$ at applied voltage of 10 V. The amplified spontaneous emission spectrum of UV-LD was also observed from pulsed current injection.

• Current Optics and Photonics
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• v.8 no.1
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• pp.80-85
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• 2024

Numerical values of the Auger coefficient and the free carrier absorption (FCA) coefficient are extracted by applying deep neural networks (DNNs) to the L-I characteristics of 850 nm GaAs/AlGaAs laser diodes. Two elemental DNNs are used to extract each coefficient sequentially. The fidelity of the extracted values is established through meticulous correlation of L-I characteristics bridging the realms of simulations and measurements. The methodology presented in this paper offers a way to accurately extract the Auger and FCA coefficients, which were traditionally treated as fitting parameters. It is anticipated that this approach will be applicable to other types of opto-electronic devices as well.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.300.2-300.2
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• 2014

테라헤르쯔(terahertz : THz)파는 0.1~10 THz 의 범위로 적외선과 방송파 사이에 광대역 주파수 스펙트럼을 차지하고 있으며 직진성, 투과성, 그리고 낮은 에너지(meV)를 가지고 있어 비 파괴적이고 무해한 장점을 지니고 있다. Ti:sapphire laser와 같은 femto-pulse source 등이 많은 발전이 되어 현재 많은 연구와 발전이 이루어지고 있다. femto-pulse source를 이용한 THz 응용에서는 높은 저항, 큰 전자이동도, 그리고 아주 짧은 전하수명의 기판을 요구하는데 저온에서 성장한(low-temperature grown : LT) InGaAs는 격자 내에 Gallium 자리에 Arsenic이 치환 하면서 AsGa antisite가 발생하여 전하수명을 짧아지는 것을 응용하여 가장 많이 이용되고 있다. 본 연구에서는 보다 높은 저항을 얻기 위하여 molecular beam epitaxy를 이용하여 semi-insulating InP:Fe 기판위에 격자 정합된 LT-InGaAs:Be/InAlAs multi quantum well (MQW)를 well과 barrier를 가각 $10{\mu}m$ 씩 100주기 성장을 하였고 Ti와 Au를 각각 30, $200{\mu}m$로 dipole antenna를 제작 하였다. 이 때 Ti:sapphire femto-pulse laser (30 fs/90 MHz)를 excitation source로 사용하였을 때 9000 pA로 LT-InGaAs epilayer (180 pA)보다 50배 이상 큰 전류 신호를 얻을 수 있었다. THz 발생과 검출을 초소형, 초경량, 고효율로 하기 위해서는 fiber-optic를 이용해야 하는데 이때 분산과 산란 손실이 가장 적은 1550 nm 대역에서 많은 연구가 이루어 졌다. 780, 1560 nm의 mode-locking laser (90 fs/100 MHz)를 사용하여 현재 많이 이용되고 있는 Ti:sapphire femto-pulse laser와 비교하여 THz 특성 변화를 확인하는 연구를 진행 하고 있다.

• Current Optics and Photonics
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• v.6 no.2
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• pp.191-195
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• 2022

We investigate the lateral far-field pattern characteristics, including divergence angle change and far-field pattern analysis as output power increases, of narrow-emitter-width 850 nm GaAs/AlGaAs laser diodes (LDs). Each LD has a cavity of 1200 and 1500 ㎛ and narrow emitter width of 2.4 ㎛ for the top and 4.6 ㎛ for the bottom. The threshold currents are 35 and 40 mA, and L-I kinks appear at power levels of 326 and 403 mW, respectively. The divergence angle tends to increase due to the occurrence of first-order lateral mode and the thermal lensing effect. But with the L-I kink, the divergence angle decreases and the far-field pattern becomes asymmetric. This is due to coherent superposition between the fundamental and the first-order lateral mode. We provide detailed explanations for these observations based on high-power laser diode simulation results.

• The Journal of Korean Physical Therapy
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• v.15 no.3
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• pp.16-44
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• 2003

Skeletal muscle regeneration is a vital process for various muscle myopathies and muscular adaptation to physiological overload. Angiogenesis is the key event in the process of muscle regeneration, and vascular endothelial growth factor(VEGF) plays an important role in it. The purpose of this study was to evaluate the effect of GaAlAs(830nm) laser and immunoreactivity of VEGF on angiogenesis after muscle contusion injury. Muscle contusion injury was induced in the triceps surae muscle by dropping a metal bead(31.4g). GaAlAs laser irradiation(power 20 mW, frequency 2000 Hz, treatment time 15 min) was applied directly to the skin of injured muscle daily for seven days. The experimental group I was irradiated immediately by laser after injury, whereas the experimental group II was irradiated after 1 day of injury. The control group was non-irradiated. The results of this study were as follows. 1. In morphological observation, there were no significant changes in experimental and control groups for 7 days. At 3 days, however, the splited muscle fibers were observed in experimental groups, and the muscle atrophy and granular tissue viewed at 7 days in control group. 2. The VEGF was expressed in muscle fiber that located in the interspace between gastrocnemius and soleus muscles. As the time coursed, the immunoreactivity of VEGF also seemed to be strong in the individual muscle fibers. 3. The experimental group I & II showed higher immunoreactivity of VEGF than control group(p<0.05). Then, the experimental group I showed higher than group II especially(p<0.05). These data suggest GaAlAs semiconduct diode laser irradiation(830nm) enhanced angiogenesis in the skeletal muscle induced contusion injury, and immediate laser irradiation after injury promoted the angiogenesis greatly than after 1 day of injury.

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.5
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• pp.419-424
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• 2002

After the patterning and probe process of wafer have been achieved, the dicing processing is necessary to separate chips from a wafer. The dicing process cuts a semiconductor wafer to lengthwise and crosswise directions to make many chips. The existing general dicing method is the mechanical cutting using a narrow circular rotating blade impregnated diamond particles or laser cutting. Inferior goods can be made by the mechanical or laser cutting unless several parameters such as blade, wafer, cutting water and cutting conditions are properly set. Moreover, we can not apply these general dicing method to that of GaN wafer, because the GaN wafer is harder than general semiconductor wafers such as GaAs, GaAsP, AIGaAs and so forth. In order to overcome these problems, this paper describes a new wafer dicing method using fixed diamond scriber and precision servo mechanism.

• Korean Journal of Optics and Photonics
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• v.2 no.2
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• pp.67-73
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• 1991

The unsaturated signal gain, signal gain bandwidth, and saturation power which are important parameters determining characteristics of the semiconductor laser amplifier were measured for an AlGaAs Fabry-Perot cavity type laser amplifier and compared with the results of Fabry-Perot formula. The unsaturated signal gain 25 dB is obtained near oscillation thereshold current at $0.7\mu\textrmW$ input power. The corresponding signal gain bandwidth was about 3 GHz. Also. We measured the variation of the saturation signal gain and saturation power.

• Current Optics and Photonics
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• v.3 no.5
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• pp.445-450
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• 2019

The influence of high-power laser diode (HPLD) emitter width on the device performance is investigated for 975-nm (In,Ga)(As,P)/(Al,Ga)As broad-area HPLDs, using self-consistent electro-thermal-optical simulation. To guarantee the simulation's accuracy, simulated results are matched with the measured results for a sample HPLD with fitting parameters. The influences of HPLD emitter width on temperature distribution, output power, and the beam product parameter (BPP) are analyzed for three different emitter widths of 50, 70, and $90{\mu}m$. It is found that a device with smaller emitter width exhibits both thermal rollover and thermal blooming at lower output power, but smaller BPP.

• Journal of Korean Physical Therapy Science
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• v.10 no.1
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• pp.180-189
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• 2003

The experiments were designated to evaluate the anti-nociceptive effect of low power laser stimulation on acupoint or non-acupoint using arthrogenic solution induced poly arthritis animal model. Evaluation of potential antinociceptive effect of low power laser on arthritis has employed measurements of the foot bending test, the development of either thermal or mechanical hyperalgesia following the arthritis induction. The analysis of thermal hyperalgesia includes Hargreaves's method. Randall-Sellitto test was utilized for evaluating mechanical hyperalgesia. In addition, the antinociceptive effect of low power laser stimulation on arthritis induced spinal Fos expression was analyzed using a computerized image analysis system. The results were summerized as follows: 1. In laser stimulation on acupoint treated animal, laser stimulation dramatically inhibited the development of pain in foot bending test as compared to those of non acupoint treated animal group and non treated animal group. 2. The threshold of thermal stimulation was significantly increased by low power laser stimulation on acupoint as compared to that of non treated control group. 3. Laser stimulation on acupoint dramatically attenuated the development of mechanical hyperalgesia as compared to that of non treated group. 4. Low power laser stimulation on acupoint significantly suppressed arthritis induced Fos expression in the lumbar spinal cord at 3 week post arthritis induction. In conclusion, the results of the present study demonstrated that low power laser stimulation on acupoint has potent anti-nociceptive effect on arthritis. Additional supporting data for an antinociceptive effect of laser stimulation was obtained using Fos immunohistochemical analysis on spinal cord section. Those data indicated that laser stimulation induced antinociception was mediated by suppression of spinal neuron activity in pain sensation.