• Title, Summary, Keyword: Pulsed Laser

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A Study on the Antibacterial Effects of Pulsed Nd: YAG Laser Irradiation to Streptococcus Mutans (Pulsed Nd : YAG Laser 조사의 Streptococcus mutans에 대한 효과)

  • Woo-Cheon Kee
    • Journal of Oral Medicine and Pain
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    • v.22 no.1
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    • pp.15-22
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    • 1997
  • In order to investigate the antibacterial effects of pulsed Nd:YAG Laser concerning to Streptococcus mutans, Streptococcus mutans was cultured and standardized and plated in 96 well plates. After that, black dye and chlorhexidine were applied and pulsed Nd:YAG Laser was irradiated to plates. Experimental groups which was applied with black dye and chlorhexidine were divided into 5 groups by concentration. And experimental groups and control group were subdivided as unlased and lased of 20, 40, and 60J. After laser irradiation, All groups were plated in agar plates and incubated for 18 hours. Bacterial colonies were counted and analysed comparitively, and the temperature of culture medium was measured on every laser irradiation. The results were obtained as follows; 1. In case of laser irradiation only, there is no significant reduction in number of Streptococcus mutans by irradiated energy of laser. 2. In case of black dye application, there is no difference by concentration of black dye but there is decrease when applied Laser and black dye simultaneously. 3. When applied chlorhexidine, the number of Streptococcus mutans was decreased according to increase of concentration, but there is no difference by irradiated energy of laser. 4. The temperature of culture medium was increased according to increase of irradiated energy of Laser, and the number of Streptococcus mutans was reduced remarkably just above 50 centigrade and killed above 70 centigrade. As above results, pulsed Nd:YAG Laser has well-absorbing affinity to black dye. And antibacterial effect of pulsed Nd:YAG Laser against Streptococcus mutans is seemed to be due to increase of temperature.

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Micro Machining of Aluminium using Pulsed Laser Beam (레이저빔을 이용한 알루미늄의 미세가공)

  • Shin, Hong Shik
    • Journal of Institute of Convergence Technology
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    • v.4 no.2
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    • pp.41-45
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    • 2014
  • Micro fabrication technologies of aluminium have been required to satisfy many demands in technology fields. Pulsed laser beam machining can be an alternative method to accomplish the micro machining of aluminium. Pulsed laser beam can be applied to micro machining such as micro drilling and milling. Using pulsed laser beam, the machining characteristics of aluminium in micro drilling and milling were investigated according to average power, repetition rate, moving speed of spot. The laser beam machining with the optimal conditions can achieve precise micro figures. As a result, micro pattern, text and structures on aluminium surface was successfully fabricated by pulsed laser beam machining.

Wound Healing After Gingivectomy Using Pulsed Nd : YAG Laser In The Rat (백서에서 Pulsed Nd : YAG Laser에 의한 치은절제술후의 치유양상)

  • Kim, Ok-Su;Chung, Hyun-Ju
    • Journal of Periodontal and Implant Science
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    • v.26 no.1
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    • pp.293-308
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    • 1996
  • Recently, dental laser have been applied for removal of soft tissues, hemostasis and blood coagulation, removal of benign and malignant tumor, treatment of leukoplakia, aphthous ulcer and herpetic lesion, implant second surgery, removal of granulation tissue, frenectomy, clinical crown lengthening, gingivectomy, gingivoplasty, and treatment of dentin hypersensitivity. Even though the frequency of laser treatment is increasing, the research on the healing process after gingivectomy using pulsed Nd : YAG laser is very rare. The purpose of this study was to observe and compare the wound healing after gingivectomy using scalpel and pulsed Nd : YAG laser in the rat. Gingivectomy was performed using pulsed Nd : YAG laser(SUNRISE Technologies, U.S.A., 1.5 Watts, 10 pps) on the buccal gingiva of right maxillary first molar and using scalpel(No.12) on the contralateral side. Those sites treated by surgical scalpel were designated as the control, and by pulsed Nd : YAG laser as the experimental group. Animals were sacrificed at 1, 2, 3, 5, 7, 11 and 14 days postoperatively, and specimens were histologically observed under light microscope. The results were as follows : 1. Clinical observation Normal color and shape were observed at the 5th day ill the control group and the 7th day in the experimental group. 2. Histologic findings 1) In the control group, denser inflammatory infiltration was observed. 2) Epithelialization started at the 2nd day in the control group, similar to the experimental group, and completed at the 11th to the 14th day postoperatively. 3) In the experimental group, connective tissue showed the vacuole formation and degenerative change during early healing period. Healing of connective tissue was slower in the experimental group than in the control group by 2 days. 4) In the both groups, wound healing was completed at the 2nd week. From this study, gingivectomy using pulsed Nd : YAG laser seems to result in a little delayed wound healing process, compared to the gingivectomy using scalpel. Considering the clinical advantages of laser surgery, pulsed Nd : YAG laser might be useful device for gingivectomy.

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Numerical simlation of nanosecond pulsed laser ablation in air (대기중 나노초 펄스레이저 어블레이션의 수치계산)

  • 오부국;김동식
    • Journal of Korean Society of Laser Processing
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    • v.6 no.3
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    • pp.37-45
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    • 2003
  • Pulsed laser ablation is important in a variety of engineering applications involving precise removal of materials in laser micromachining and laser treatment of bio-materials. Particularly, detailed numerical simulation of complex laser ablation phenomena in air, taking the interaction between ablation plume and air into account, is required for many practical applications. In this paper, high-power pulsed laser ablation under atmospheric pressure is studied with emphasis on the vaporization model, especially recondensation ratio over the Knudsen layer. Furthermore, parametric studies are carried out to analyze the effect of laser fluence and background pressure on surface ablation and the dynamics of ablation plume. In the numerical calculation, the temperature, pressure, density, and vaporization flux on a solid substrate are obtained by a heat-transfer computation code based on the enthalpy method. The plume dynamics is calculated considering the effect of mass diffusion into the ambient air and plasma shielding. To verify the computation results, experiments for measuring the propagation of a laser induced shock wave are conducted as well.

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Pulsed-laser-diode Intermittently Pumped 2-㎛ Acousto-optic Q-switched Tm:LuAG Laser

  • Wen, Ya;Jiang, Yan;Zheng, Hao;Zhang, Hongliang;Wang, Chao;Wu, Chunting;Jin, Guangyong
    • Current Optics and Photonics
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    • v.4 no.3
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    • pp.238-246
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    • 2020
  • The heat distribution in crystals in a 2-㎛ acousto-optic Q-switched Tm:LuAG laser pumped by pulsed-laser-diode (pulsed-LD) intermittent-pumping technology was analyzed using COMSOL software. The thermal lensing effect of the Tm:LuAG crystal can be mitigated by pulsed-LD intermittent-pumping techniques. An experimental setup using this kind of approach achieved maximum output energy of 8.31 mJ, minimum pulse width of 101.9 ns, and highest peak power of 81.55 kW, reached at a Q-switched repetition rate of 200 Hz. It offers significant improvement of performance of the output laser beam, compared to pulsed-LD double-ended pumping technology at the same repetition rate.

Barrier Layers and Pulsed Laser Annealing Effects on TFEL Device with Cu and Ag co-doped SrS blue Phosphor Layer

  • Nam, Tae-Sung;Liew, Shan-Chun;Koutsogeorgis, Demosthenes C;Cranton, Wayne M
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.910-913
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    • 2003
  • In order to enhance performance, stability, and brightness of inorganic blue-light emitting EL device, barrier layer structure and pulsed laser annealing(PLA) treatment were introduced. The barrier layer structure was utilized for improving brightness of the device and instead of thermal annealing, pulsed laser annealing process was used. From this study, optimum barrier layer thickness and number of pulsed laser irradiation are established.

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Analysis of Variation in the Surface Morphology of Aluminum Alloy by Repetitive Pulsed-laser Irradiation (반복적인 펄스레이저 조사에 의한 알루미늄 합금의 표면상태 변화분석)

  • Choi, Sung-Ho;Kim, Chung-Seok;Jhang, Kyung-Young;Shin, Wan-Soon
    • Journal of the Korea Institute of Military Science and Technology
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    • v.14 no.5
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    • pp.897-903
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    • 2011
  • The objective of this study is to investigate the thermal behavior on material surface and the variation in the surface morphology of aluminum 6061 alloy by the Nd:YAG pulsed-laser irradiation. First, we predicted the surface temperature variation during pulsed-laser irradiation by using the two dimensional finite element analysis. When the pulsed-laser of 133 mJ energy and 5 ns pulse duration is irradiated on the surface of aluminum alloy, the material surface is thought to be melting because the surface temperature rises steadily up to about $660^{\circ}C$ exceeding the melting point. Also, the experimental results show that the solidification microstructure has been developed clearly after surface melting. Second, the diameter of melted zone was analysed by finite element analysis and measured by OM(Optical Microscopy). It increased logarithmically with increase in the number of laser irradiation. In addition, AFM(Atomic Force Microscopy) measurement showed an increase in the average surface roughness during pulsed-laser irradiation.

Study on Characteristics of Micro Patterned Copper Electrodeposition according to Parameters in Laser Beam Machining (레이저빔 가공 인자에 따른 구리도금 미세 패터닝 특성 연구)

  • Shin, Hong Shik
    • Journal of Institute of Convergence Technology
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    • v.5 no.2
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    • pp.21-25
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    • 2015
  • This paper proposes a fabrication process of deposited layer with micro patterns that uses a combination of a pulsed laser beam machining and an electrodeposition. This process consists of the electrodeposition and the laser beam machining. The deposited layer on metal can be selectively eliminated by laser ablation. As a result, the deposited layer with micro patterns can be fabricated without a mask. The characteristics of the deposited layer on stainless steel were investigated according to the average power and marking speed in the pulsed laser beam machining. The optimal laser beam conditions for precise micro patterning of the deposited layer were determined. Finally, the deposited copper layer with micro text was successfully fabricated by the pulsed laser beam machining.

Optical Properties of Silicon Nanoparticles and $C_{60}$ Thin Films Prepared by Pulsed Laser Ablation (Pulsed Laser Ablation으로 제작한 $C_{60}$ 및 Si 박막의 광학적 특성 분석)

  • Kim, M.S.
    • Journal of the Korea Society For Power System Engineering
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    • v.9 no.4
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    • pp.118-123
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    • 2005
  • We have investigated the fabrication of Si nanoparticles and $C_{60}$ thin films by pulsed laser ablation. By atomic force microscopy(AFM), the laser-deposited $C_{60}$ thin film was verified to have surface far smoother than the surfaces of films produced by the conventional evaporation method. The Si deposited at a He atmosphere of 0.2 Torr was with about $60{\AA}$ height of the Si nanoparticles, suggesting that it was uniformly deposited. We observed visible green emissions spectra in the $Si/C_{60}$ multilayer films after laser annealing. It is considered that this green emissions is occurred from SiC particles, which is produced reaction of Si nanoparticles with $C_{60}$ by laser annealing.

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The high repetition operating characteristics of pulsed Nd:YAG laser by alternating charge-discharge system (펄스형 Nd:YAG 레이저의 교번 충.방전 방식에 의한 고반복 동작특성)

  • Kim, W.Y.;Park, K.R.;Kim, B.G.;Hong, J.H.;Kang, U.;Kim, H.J.
    • Proceedings of the KIEE Conference
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    • pp.2204-2206
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    • 1999
  • Pulsed Nd:YAC laser is used widely for materials processing and instrumentation. It is very important to control the laser energy density in materials processing by a pulsed Nd:YAG laser. A pulse repetition rate and a pulse width are regarded as the most dominant factors to control the energy density of laser beam. In this study, the alternating charge-discharge system was designed to adjust a pulse repetition rate. This system is controlled by one chip microprocessor and allows to replace an expensive condenser for high frequency to a cheap condenser for low frequency. In addition. we have investigated the current pulse shape of flashlamp and the operating characteristics of a pulsed Nd:YAG laser. As a result, it is found that the laser output of the power supply using the alternating charge-discharge system is not less than that of typical power supply. As the pulse repetition rate rises from 30pps to 120pps by the step of 30pps at 1200V, it is found that the laser efficiency decreases but the laser output power increases about 6W at each step.

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