• Title, Summary, Keyword: Pulsed Laser

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The output characteristics of pulsed Nd:YAG laser with voltage variable capacitor-charging system (충전전압 가변방식을 이용한 펄스형 Nd:YAG 레이저의 출력특성에 관한 연구)

  • Moon, D.S.;Hong, J.H.;Song, K.Y.;Song, W.J.;Kim, K.H.;Kim, H.J.
    • Proceedings of the KIEE Conference
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    • pp.1703-1705
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    • 2001
  • The pulsed Nd:YAG laser is used widely for materials processing and medical instrument etc. It is important to control the laser energy in those fields using a pulsed Nd:YAG laser. In this paper, constant-frequency current resonant half-bridge inverter and Cockcroft-Walton circuit are used to charge the energy storage capacitor variably. This laser power supply is designed and fabricated which has no high-voltage transformer, less switching losses, compact size and capability in varying the laser output power. Also, the output characteristics of this Nd:YAG laser system are investigated. The tested results are described.

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Glass Drilling using Laser-induced Backside Wet Etching with Ultrasonic Vibration (초음파 진동과 레이저 후면 에칭을 통한 유리 구멍 가공)

  • Kim, Hye Mi;Park, Min Soo
    • Journal of the Korean Society for Precision Engineering
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    • v.31 no.1
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    • pp.75-81
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    • 2014
  • Laser beam machining has been known as efficient for glass micromachining. It is usually used the ultra-short pulsed laser which is time-consuming and uneconomic process. In order to use economic and powerful long pulsed laser, indirect processing called laser-induced backside wet etching (LIBWE) is good alternative method. In this paper, micromachining of glass using Nd:YAG laser with nanosecond pulsed beam has been attempted. In order to improve shape accuracy, combined processing with magnetic stirrer has been widely used. Magnetic stirrer acts to circulate the solution and remove the bubble but it is not suitable for deep hole machining. To get better effect, ultrasonic vibration was applied for improving shape accuracy.

A Study on the Anesthetic Effects of Pulsed Nd:YAG Laser Irradiation to the Oral Mucosa and the Teeth (Nd:YAG 레이저 조사에 의한 치아 및 구강점막의 마취효과)

  • 최재갑
    • Journal of Oral Medicine and Pain
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    • v.23 no.1
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    • pp.1-9
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    • 1998
  • The aim of the study was to evaluate the anesthetic Effecs of pulsed Nd:YAG laser irradiation to the oral mucosa and the teeth. Twenty subjects who didn't have a history of significant systemic or current oral disease were included in this study. All the subjects were divided randomly into the experimental group and the control group with 10 for each group. Pain thresholds were measured with Weighted Needle Pinprick Sensory Threshold Test for the mucosal surface of lower lip and with electric pulp test for the upper right central incisor respectively, before and immediately after pulsed Nd:YAG laser irradiation in the condition of 2 watt, 20pps for 2 minute at 10mm distance. The experiment was double-blinded clinical trial. The results were as follows : 1. The mean pain threshold of the mucosal surface of lower lip for Weighted Needle Pinprick Sensory Threshold Test was 2.94(1.00g for the contral group respectively, and there was no statistical difference between two groups. 2. The mean pain threshold of the mucosal surface of lower lip was significantly increased immediately after pulsed Nd:YAG laser irradiation. 3. The mean pain threshold of the upper right central incisor for eledtric pulp test was 34.50(4.97V in the experimental group and 34.00(13.08V in the control group respectively, and there was no statistical difference between two groups. 4. The mean pain threshold of the upper right central incisor was significantly increased immediately after pulsed Nd:YAG laser irradiation.

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Numerical Analysis of Optical Damage in Dielectrics Irradiated by Ultra-Short Pulsed Lasers (극초단 펄스 레이저에 의한 절연체의 광학 손상 해석)

  • Lee, Seong-Hyuk;Kang, Kwang-Gu;Lee, Joon-Sik;Choi, Young-Ki;Park, Seung-Ho;Ryou, Hong-Sun
    • Proceedings of the KSME Conference
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    • pp.1213-1218
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    • 2004
  • The present article reports extensive numerical results on the non-local characteristics of ultra-short pulsed laser-induced breakdowns of fused silica ($SiO_{2}$) by using the multivariate Fokker-Planck equation. The nonlocal type of multivariate Fokker-Planck equation is modeled on the basis of the Boltzmann transport formalism to describe the ultra-short pulsed laser-induced damage phenomena in the energy-position space, together with avalanche ionization, three-body recombination, and multiphoton ionization. Effects of electron avalanche, recombination, and multiphoton ionization on the electronic transport are examined. From the results, it is observed that the recombination becomes prominent and contributes to reduce substantially the rate of increase in electron number density when the electron density exceeds a certain threshold. With very intense laser irradiation, a strong absorption of laser energy takes place and an initially transparent solid is converted to a metallic state, well known as laser-induced breakdown. It is also found that full ionization is provided at intensities above threshold, all further laser energy is deposited within a thin skin depth.

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A Study on Hair Removal Characteristics Using a Long-pulsed Alexandrite Laser

  • Choi Jin-Young;Kim Sang-Gil;Park Jong-Woong;Park Sung-Joon;Kim Hee-Je
    • KIEE International Transactions on Electrophysics and Applications
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    • v.5C no.1
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    • pp.33-38
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    • 2005
  • Recently, lasers have become widely used throughout the medical treatment field. Several types of lasers have been used for the purpose of hair removal since the Alexandrite laser was approved by the FDA (Food & Drug Administration) for clinical epilation. In this study, a long-pulsed Alexandrite laser system for hair removal adopting a multi-discharge method in which three flash lamps are turned on consecutively was designed and fabricated. This laser system shows the technology that makes it possible to create extended pulse by turning on three flash lamps consecutively. With this technique, the pulse width can be varied from 4ms∼10ms. Then using this Alexandrite laser system with the pulse width 10ms and the beam size 7mm, hair removal was performed on the back portion of a human hand and leg. This study shows that treatment by the long-pulsed Alexandrite laser produces hair removal with no relevant side effects.

TEMPERATURE CHANGES OF IMPLANT SURFACE IN SECOND STAGE SURGERY WITH DETAL LASER : IN VITRO STUDY (레이저를 이용한 임프란트 이차수술시 온도변화에 관한 실험적 연구)

  • Ahn, Hyun-Jeong;Kim, Hyoun-Chull;Choi, Byeong-Gap;Song, Eon-Hee;Kim, Rae-Gyoung
    • The Journal of Korean Academy of Prosthodontics
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    • v.37 no.2
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    • pp.256-268
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    • 1999
  • Submerged implants require secondary surgical uncovering of implants after healing period of 3-6 months. In surgical methods, there are surgical scalpel, tissue punch, electro-surgical, and laser-used uncovering, and so forth The objectives of this study are investigation and assessment of 1) thermal change in clinical application for uncovering of HA-coated implant and pure titanium implant irradiated by pulsed Nd-YAG, $CO_2$, and Er-YAG laser. 2) surface change of cover screws aaer irradiation using laser energy. The temperature of apex & side wall of implants were recorded at 10sec, 20sec, 30sec after 30sec irradiation to implant healing screw; 1) pulsed Nd-YAG laser; 2W, 20pps, contact mode 2) $CO_2$ laser; water-infused & non-water infused state, 2.5-3.5W, contibuous mode, noncontact mode 3) $CO_2$ laser ; non-water infused state, 3W, superpulse, noncontact. mode 4) Er-YAG laser; (1) non-water infused state, 10pps, 60mj, contact mode (2) water-infused state, 10pps, 60mj, 80mj, 101mj, contact mode. According to the results of this study, pulsed Nd-YAG laser is not indicated because of increased thermal change and pitting of metal surface of implant cover screw. By contrast, $CO_2$ laser & Er-YAG laser are presumed to indicate because of narrow range of thermal change & near abscence of thermal damage of metal surface. Dental laser is thought to be much helpful to surgical procedure when it is used as optimal power and time condition considering characteristics and indications of each laser. Further research is needed to verify that these techniques are safe and beneficial to implant success.

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Effects of Two-Step Annealing Process on the Pulsed Laser Ablated Lead Zirconate Titanate Thin Films

  • Rhie, Dong-Hee
    • KIEE International Transactions on Electrophysics and Applications
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    • v.3C no.2
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    • pp.43-47
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    • 2003
  • Lead zirconate titanate (PZT) thin films were fabricated by the pulsed laser ablation deposition (PLAD) method onto Pt/Ti/SiO$_2$/Si substrates. Crystalline phases as well as preferred orientations in PZT films were investigated by X-ray diffraction analysis (XRD). The well-crystallized perovskite phase and the (101) preferred orientation were obtained by two-step annealing at the conditions of $650^{\circ}C$, 1 hour. It was found that the temperature for the pulsed laser ablated PZT films annealed via a two-step annealing process can be reduced 20$0^{\circ}C$ compared to that of the conventional three-step annealing temperature profile for enhancing the transformation of the perovskite phase. The remanent polarization and the coercive field of this film were about 20 $\mu$C/$\textrm{cm}^2$ and 46 kV/cm, while the dielectric constant and loss values measured at 1 KHz were approximately 860 and 0.04, respectively. The interesting phenomena of this film, such as vertical shift in hysteresis curve, are also discussed.

Characteristics of ferroelectric properties of $(Bi,Ce)_4Ti_3O_{12}$ thin films deposited by pulsed laser deposition (Pulsed laser deposition 방법으로 증착된 $(Bi,Ce)_4Ti_3O_{12}$ 박막의 강유전특성 분석)

  • 오영남;성낙진;윤순길
    • Proceedings of the Materials Research Society of Korea Conference
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    • pp.37-37
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    • 2003
  • Ferroelectric random acess memories (FeRAMs) 재료로 주목받고 있는 강유전 물질은 이미 여러 해 전부터 많은 물질들에 대해 연구가 진행되어 왔다. 그 중 낮은 공정 온도를 가지며 큰 remanent polarization 값을 갖는 lead zirconium titanate (PZT) 박막에 대해 많은 연구가 진행되고 있다. 하지만 Pt 기판위에 증착된 PZT 박막은 높은 피로 현상을 보이는 문제가 있다. 최근 Pulsed laser deposition이나 metal-organic vapor phase epitaxy (MOVPE) 등의 방법에 의해 epitaxial substituted-$Bi_4Ti_3O_{12}$ (La, Nd) 박막에 대해 보고가 되고 있다. 본 연구에서는 높은 remanent polarization 값을 갖는 $(Bi,Ce)_4Ti_3O_{12}$ (BCT) 박막을 pulsed laser deposition 방법을 사용하여 증착하였다. 또한 Bismuth의 양을 변화시켜 Bismuth의 양에 따른 remanent polarization의 변화를 확인하여 보았다. 사용된 기판은 Pt/$TiO_2$/$SiO_2$/Si 기판을 사용하였다.

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