• Title, Summary, Keyword: ND:YAG LASER

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Characteristics of Nd:YAG Laser Pumped by cw Ti:sapphire Laser and Its Passive Q-switching with Cr4+:YAG as Saturable Absorber (Cr4+:YAG 포화 흡수체를 이용한 Ti:sapphire 레이저 여기 Nd:YAG 레이저의 수동형 Q-switching 특성)

  • 안범수;추한태;김규욱
    • Korean Journal of Optics and Photonics
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    • v.15 no.3
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    • pp.263-267
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    • 2004
  • We have investigated the characteristics of a Nd:YAG laser pumped by a cw Ti:sapphire laser. When the pumping power of the Ti:sapphire laser was 850 ㎽, the maximum output power of the Nd:YAG laser was 450 ㎽. As a result, the slope efficiency for the output power of the Nd:YAG laser was measured to be 56%. We have also investigated the characteristics of a passively Q-switched Nd:YAG laser by using a Cr$^{4+}$:YAG as saturable absorber with initial transmission of 90%. The maximum average output power of 200 ㎽ was obtained with repetition rate of 23.8 KHz and pulse width of 17.0 ns.

An Experimental Study on the Effect of Laser to Bond Strength between Composite Resin and Bovine Teeth (우치치질에 레이저조사시 레진과의 결합강도에 관한 연구)

  • Cho, Ju-On;Song, Kwang-Yeob;Park, Charn-Woon
    • The Journal of Korean Academy of Prosthodontics
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    • v.27 no.2
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    • pp.155-172
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    • 1989
  • The purpose of this study is to measure the bonding strength at the enamel and dentin of extracted bovine incisors when they are irradiated by W Nd: YAG, EoQ Nd: YAG, and CW $CO_2$ laser, etched and then attached by composite resin. The laser-irradiated surface, the etched surface after the laser-irradiation and the interface of the treated surface and resin are observed by using scanning electron microscope. The NP Nd:YAG laser is used at the peam power of 207 KW. The EOQ Nd: YAG laser is used at the peak power of 1.15Mk. The CW $CO_2$ laser is used at the energy output of 5W and 10W in enamel; in dentin, at the energy output of 2W. The obtained results were as follows: 1. The shear bond strength of enamel decreased in the following order: EOQ Nd:YAG laser group, NP Nd:YAG laser group, CW $CO_2$ laser groups, unlased group. The unlased group showed a significant difference from EOQ Nd:YAG laser group (P<0.01), NP Nd:YAG laser group (P<0.05), but no significant difference from CW $CO_2$ laser group (P>0.05). 2. The shear bond strength of dentin decreased in the following order: CW $CO_2$ laser group, NP Nd:YAG laser group, unlased group, EOQ Nd:YAG laser group. The unlased group showed a significant difference from CW $CO_2$ laser group (P<0.01), but no significant difference from Nd:YAG laser groups (P>0.05). 3. The scanning electron microscope of enamel revealed irregular microcrack and pore at the surface in the NP Nd:YAG laser group and CW $CO_2$ laser group, but the crackless flat surface in the EOQ Nd:YAG laser group. 4. The scanning electron microscope of dentin revealed obstruction of in most of dentinal tubule and decrease of diameter. 5. The scanning electron microscope of the interface of resin and enamel revealed prominent penetration of resin tag in the EOQ Nd:YAG laser group.

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Metallic pattern Heat treatment by means of CW Nd:YAG Laser (CW Nd:YAG 레이저를 이용한 금형열처리)

  • Shin, Ho-Jun;Yoo, Young-Tae;Oh, Yong-Seak;Ro, Kyoung-Bo
    • Proceedings of the KSME Conference
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    • pp.1898-1904
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    • 2003
  • Laser heat treatment is an effective technique used to improve the tribological properties and also to increase the service life of automobile components such as camshafts, crankshatfs, lorry brake drums and gears. High power $CO_{2}$ lasers and Nd:YAG lasers are employed for localized hardening of materials and hence are of potential application in the automobile industries. The heat is conducted rapidly into the bulk of the specimen causing self-quenching to occur and the formation of matrensitic structure. In this investigation, the microstructrual features occurring in Nd:YAG laser hardening SM45C and $STD_{11}$ steel are discussed with the use of optical microscopic and scanning electron microscopic analysis. Moreover, This paper describes the optimisation of the processing parameters for maximum hardened depth of SM45C and $STD_{11}$ steel specimens of 10mm thickness by using CW Nd:YAG laser.

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Optimization of Q-switched Operation at a Laser-Diode Pumped Nd:YAG Ceramic Laser (반도체레이저 여기 세라믹 Nd:YAG 레이저에서 Q-스위칭 동작 최적화)

  • Shin, Dong-Joon;Kim, Byung-Tai;Kim, Duck-Lae
    • Korean Journal of Optics and Photonics
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    • v.19 no.4
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    • pp.320-326
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    • 2008
  • The output characteristics of a laser-diode pumped electrooptic Q-switched Nd:YAG ceramic laser were investigated. The output energy of a Q-switched Nd:YAG ceramic laser was optimized under an output coupler reflectivity of 77%, a laser-diode pulse width of $1,000\;{\mu}s$, and a delay time of $985\;{\mu}s$. The output energy of the Q-switched pulse was measured to be 0.35 mJ with a pulse width of 4 ns under a pump energy of 17.9 mJ. The output efficiency and the peak power were 1.9% and 87.5 kW, respectively.

ButWelding Characteristics of SM45C and SUS 304 using a Nd:YAG laser (SM45C와 SUS304의 Nd:YAG 레이저 맞대기용접특성)

  • Yoo, Young-Tae;Ro, Kyoung-Bo;Shin, Ho-Jun;Kim, Ji-Hwan;Oh, Young-Seok
    • Proceedings of the KSME Conference
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    • pp.1302-1308
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    • 2003
  • Welding characteristics of austienite 304 stainless steel and SM45C using a continuous wave Nd:YAG laser are experimentally investigated. Laser beam welding is increasingly being used in welding of structural steels. The laser welding process is one of the most advanced manufacturing technologies owing to its high speed and deep penetration. This paper describes the weld ability of SM45C carbon steel and austienite 304 stainless steel for machine structural use by Nd:YAG laser.

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Micromachining of PZT using Nd:YAG laser (Nd:YAG 레이저를 이용한 PZT의 미세가공)

  • Hong J.U.;Lee J.H.;Suh J.;Shin D.S.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.223-224
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    • 2006
  • In this study, we have investigated the micromachining of PZT to fabricate interdigitated electrodes of electro active material actuator using Nd:YAG laser We have observed groove shapes of PZT with changing beam power, scanning speed, gas, and so on to find optimum conditions of the laser processing for PZT grooves. As a result, this method has been applied to the laser micromachining for grooves in PZT surface, and we could have optimum parameters of Nd:YAG laser Finally it was shown that the laser micromachining of PZT can substitute fer bonding, etching and deposition processes in fabricating electro active material actuator embedded with interdigitated electrodes.

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ORTHODONTIC BRACKET SHEAR BOND STRENGTH TO Nd:YAG LASER Er:YAG LASER IRRADIATED ENAMEL (Nd : YAG 및 Er : YAG 레이저로 치아표면 조사시 브라켓 전단접착강도에 관한 실험적 연구)

  • Choi, Seung-Hoon;Yang, Won-Sik
    • The korean journal of orthodontics
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    • v.27 no.1
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    • pp.141-155
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    • 1997
  • The purpose of this study was to evaluate the effectiveness of the Nd:YAG laser and the Er:YAAG laser on etching enamel for direct bonding of orthodontic bracket. The advantages of laser etching rather than conventional acid etching are to reduce the subsurface demineralization rate, to inhibit the spillage of acid onto uninvolved ""its of enamel, and to save the clinical manipulation time involving drying, trashing and drying again. 189 freshly extracted human premolars were prepared for this research. 165 out of them were divided into 11 groups of 15 teeth. One group was acid etching and the rest groups were irradiated with Nd:YAG laser by four different energy levels(100mj 10pps, 100mj 20pps, 150mj 20pps, 200mj 20pps) and with Er:YAG laser by six different energy levels(60mj 5pps, 60mj 10pps, 100mj 10pps. 200mj 10pps, 200mj l5pps, 400mj 10pps). Shear bond strength was tested with Instron after 24 hours, one week, and three weeks. Twenty-four out of 189 teeth were divided into twelve groups untreated control, acid etching, and ten laser irradiation subgroups. And the ultrastructural enamel surfaces of each group were observed with scanning electron microscope. The results were as follows; 1. The means and the standard deviations of shear bond strength of Nd:YAG and Er:YAU laser irradiation by different energy levels were obtained. 2. Shear bond strengths of Er:YAG laser irradiation groups were higher than those of Nd:YAG laser irradiation groups at the identical energy level. 3. Maximum bond strengths was achieved at the energy of I50mj, 20pps in Nd:YAG laser irradiation groups or 60mj, 10pps in Er:YAG laser irradiation groups. 4. It was acceptible for direct bonding to irradiate lb0mj 20pps with Nd:YAG laser or to irradiate 60mj 10pps with Er:YAG laser considering the results of shear bond strength tests and SEM obsesvation.

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INHIBITORY EFFECT OF DENTAL LASERS ON THE GROWTH AND THE FUNCTION OF STREPTOCOCCUS MUTANS (각종 치과레이저의 Streptococcus mutans에 대한 증식 및 기능억제 효과)

  • Han, Kang-Seog;Kook, Joong-Ki;You, So-Young;Kim, Hwa-Sook;Park, Jong-Whi;Park, Heon-Dong;Lee, Sang-Ho
    • THE JOURNAL OF THE KOREAN ACADEMY OF PEDTATRIC DENTISTRY
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    • v.30 no.3
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    • pp.439-447
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    • 2003
  • This was performed to evaluate the inhibitory effect of laser on the growth of S. mutans. The bacterial pallets containing S. mutans KCTC 3065 were irradiated with Er:YAG laser and Nd :YAG laser by non-contact method at an intensity of 50mJ for 5 sec with the pulse repetition rates of 10Hz and 30Hz, respectively. The following results were obtained on colony count, acid producing ability, and the amount of insoluble extracellular polysaccharide synthesis. 1. The irradiation of Nd:YAG laser after photosensitization with Chinese ink inhibited the proliferation of S. mutans the most, and the irradiation of Er:YAG also inhibited the proliferation. However, the irradiation of Nd:YAG laser alone could not inhibited the proliferation of S. mutans. The pulse repetition rate did not affect significantly on the proliferation of bacteria in overall. 2. The irradiation of Nd:YAG laser after the photosensitization with Chinese ink inhibited the acid production of S. mutans the most for a certain period of time. Er:YAG laser also inhibited acid production. When Nd:YAG laser was used alone, the acid production of S. mutans was not been inhibited. The irradiation of Nd:YAG laser after photosensitization with Chinese ink inhibited the acid production ability of bacteria the most as the pulse repetition rate increased. 3. Laser irradiation did not inhibited the synthesis of insoluble extracellular polysaccharide of S. mutans. From these results, we conclude that the irradiation of Er:YAG laser and Nd:YAG laser after photosensitization with Chinese ink would inhibit the proliferation and acid production by S. mutans, which may prevent dental caries. However, this effect does not last long time so that the laser irradiation should be repeated frequently in order to obtain clinical effect; thus, this laser irradiation would not have a clinical usefulness in preventing dental caries when used solely.

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Nd:YAG 레이저를 통한 SIDE PANEL의 3겹 겹치기 레이저 용접

  • 장인성;서보신;권태용
    • Proceedings of the Korean Society of Laser Processing Conference
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    • pp.55-60
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    • 2000
  • Laser welding is an important technology in the assembly of automotive. In this paper, Nd:YAG laser welding of applications for auto body assembly will be introduced. This paper will describe characteristics of the CW Nd:YAG laser lap-joint welding, and laser welding of specific configurations for a Zinc-coated steel. Experimental results indicated that the weld quality of auto body assembly using the CW Nd:YAG laser welding technology.

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Development of a Nd;YAG Welding System and Its Applications (Nd:YAG 레이저 응접기의 국산화개발 및 응용)

  • 김철종;이종민
    • Proceedings of the Optical Society of Korea Conference
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    • pp.107-115
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    • 1989
  • A 200 W industrial Nd:YAG laser was developed and its weding applications were investigated. The important factors in designing of an industrial Nd:YAG laser were analyzed and special sedign features were explained. Also, the performance of laser weldings of Zircaloy-4, stainless steel and fine thermocouples was presented.

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