• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.365-368
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• 2001

입사면에서 발생하는 열을 효율적으로 제거하기 위하여 Yb:YAG 결정의 표면에 sapphire 창을 부착하여 레이저를 발진 시켰다. Yb:YAG 결정에서 발생하는 열이 sapphire 창을 통하여 구리판으로 전달되는 경우 와 Yb:YAG 결정의 측면에서 냉각하는 경우의 레이저 출력을 측정하여 각각의 레이저 발진 특성을 비교하여 보았다. 여기면을 sapphire 창으로 냉각하는 micro-chip Yb:YAG 레이저의 레이저 에너지 전환 효율은 38%였으며 레이저 발진 문턱값은 4 kw/mm$^2$, slope efficiency는 56%로 측정되었다. Sapphire 창을 사용하는 경우 표면에서의 열전달도는 10 W/mm$^2$이상으로 관측되었다. Yb:YAG의 도핑율, 출력경의 반사율 등을 레이저 변수를 최적화할 경우 같은 구조에서 50 W급 레이저도 발진 가능할 것으로 예상된다.

• Journal of the Korean Ceramic Society
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• v.40 no.11
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• pp.1120-1126
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• 2003

Yttrium Aluminum Garnet (YAG) powders were prepared by precipitation of Y hydroxides during milling of alumina powders. The powder calcined at 1200$^{\circ}C$ for 4 h contained a small amount of Yttrium Aluminum Monoclinic (YAM) in addition to YAG. However, phase-pure YAG was obtained in the compact of the milled powder with an average particle size of 0.57 ${\mu}$m at 1300$^{\circ}C$, which is much lower than those (l500∼1600$^{\circ}C$) for a mixed oxide method. The powder was found to exhibit an excellent sinterability regardless of the addition of a sintering aid, SiO$_2$(350 ppm Si). The undoped sample were sintered to a relative density of 98% at l600$^{\circ}C$. In contrast, the addition of SiO$_2$ caused a considerable densification to occur at 1500$^{\circ}C$ and the relative density reached 97.7%. But the sintering aid had little effect on the densification at 1600$^{\circ}C$, showing a similar relative density to the undoped sample.

• Proceedings of the Korean Society of Laser Processing Conference
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• 1998.11a
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• pp.24-28
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• 1998

• Korean Journal of Optics and Photonics
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• v.14 no.1
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• pp.44-50
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• 2003

This paper describes the thermal effect at Nd:YAG using a laser-diode side-pumping. To detect the depolarization loss and the retardation caused by the thermal effect, a λ/4 plate is inserted between the polarizer and the Nd:YAG laser material. Using a CCD has allowed detection of the variation of the beam pattern that could analyze the change of the refractive index of the Nd:YAG laser material by the thermal effect. Through the change of the probe beam power, we know that 21% of the pumping power was converted into heat in the material. The depolarization loss was 24.7% under a temperature of $25^{\circ}C$ of the laser material and a pumping power of 15 W. The inhomogeneous distribution showed that the retardation angle was 7$^{\circ}$ in the center of the material and 19$^{\circ}$ on the edge of it. It is confirmed that the thermal effect is analyzed at the each point of the laser material and it suggests an effective method to reduce the thermal effect on the LD side-pumped laser material.

• The Journal of Korean Academy of Prosthodontics
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• v.34 no.3
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• pp.489-500
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• 1996

Pulsed Nd : YAG LASER has been applied to various fields in clinical dentistry including the treatment of peri-implantitis. However, LASER can affect properties of matter of dental implants which are important to maintaining the health of peri-implant tissue and can raise its temperature during lasing. So there have been warings of using LASER to treat peri-implantitis. But, the effects of laser on dental implants itself are not certain yet. So we measured the temperature rising, examined matter of properties by SEM and EDX before and after pulsed Nd : YAG lasing various intensity. 7 TPS implants and 7 HPS implants were used and pulsed Nd : YAG LASER was used in 0.3W, 1.0W, and 2.0W. 1. 2.0W LASER made polished neck portion of HPS implants reach $39.2^{\circ}C$ after 5 seconds lasing. 2. LASER made crater-like defects on plasma sprayed surface and surfaces were melted and divided by fragments after lasing. 3. There was no specific evidence of element change after lasing.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.7
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• pp.463-468
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• 2017

For transdermal drug delivery, needless injection system is composed of laser and microjet injector. Main mechanism of microjet injector is the laser-induced bubble. Nd:YAG and Er:YAG laser are used as a power source. Laser parameters such as pulse duration and wavelength are considered, which are core parameters to control the bubble motion. The Nd:YAG laser, pulse duration is short than bubble life time making cavitation like bubble while in Er:YAG laser, long pulse duration and high absorption in water drive bubble as a boiling bubble. Detailed motion of bubble and microjet is captured by the high speed camera. So it is observed that microjet characteristics are determined by the bubble behavior. The performance of drug delivery system is evaluated by fluorescent staining of guinea pig skin.

• Korean Journal of Optics and Photonics
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• v.26 no.1
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• pp.38-43
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• 2015

We propose a linearly polarized long-cavity Yb:YAG laser with a variable-reflectivity output coupler and investigate its output characteristics. The variable output coupler consists of a polarized beam splitter and a quarter-wave plate. The linearly polarized laser has a long cavity length of about 3.7 m. The slope efficiency of the proposed laser is 19%, and the beam quality ($M^2$) is about 1.2.

• Proceedings of the Optical Society of Korea Conference
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• 2000.08a
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• pp.222-223
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• 2000

지금까지 gold-coated 반사체, cusp-shaped 반사체, 복합 포물 반사체(CPC), 난반사 공동체 등 다양한 형태의 반사체가 횡펌핑을 이용한 Nd:YAG 레이저의 개발을 위하여 고안되어졌다. 횡여기되는 Nd:YAG 레이저의 광학적 효율은 반사체의 형태, 다이오드 레이저의 파장, Nd:YAG 결정의 지름, Nd$^3$의 도핑농도에 따라 영향을 받는다.$^{(1)}$ 본 연구에서는 고출력의 횡여기 Nd:YAG 레이저를 개발할 목적으로 광여기 공동으로 사용된 난반사 공동체의 내부지름과 레이저 매질인 Nd:YAG 결정의 흡수계수 등 매개변수를 변화시켜 흡수분포와 출력을 계산하였으며, 이러한 매개변수들이 기울기 효율에 미치는 영향을 수치 해석적으로 연구해 보았다. 광선추적법에서 사용한 매개변수 중에서 다이오드 레이저의 파장은 808 nm이고, 반사율은 90%이며, 여기 다이오드 출력은 1080 W이다. 난반사 공동체$^{(2)}$ 의 반사율은 95.7%이고, 결정의 투과율은 90%이며, 결정의 반지름은 2.5 mm이다. 사용된 여기 구조도는 그림 1과 같다. 여기헤드는 Nd:YAG 결정, 난반사 공동체, 그리고 3개의 360 W급 다이오드 어레이들로 구성되어 있다. (중략)

• 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.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.4
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• pp.660-666
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• 2003

The purpose of this study was to investigate the inhibitory effect of Er:YAG laser against the intraoral acid producing bacterium of S. mutans. Bacterial pellet containing S. mutans KCTC 3065 was irradiated by Er:YAG laser having a $650\;{\mu}m$ diameter beam by non-contact mode. Irradiated parameters were 50mJ, 10Hz and exposure time were 1s, 3s, 5s, 7s, 9s respectively. We obtained the following results of relative growth rate and acid-producing ability of S. mutans by culturing for 48hrs. 1. The growth rate of S. mutans was decreased in the group of laser irradiation compared to the control group(P<0.01). 2. The growth rate at laser irradiation group of 7s, 9s irradiation time was decreased significantly compared to the laser irradiation group of 1s, 3s, 5s irradiation time, until 12 hours(P<0.05). After 24 hours, all groups of laser irradiation were not found to be statistically different in each other. 3. The acid-producing ability of S. mutans was inhibited for a certain duration by irradiation of laser. In summary, the growth rate and acid producing ability of S. mutans decreased according to laser irradiation. This effect was directly related to the amount of irradiation time. These results suggested that Er:YAG laser had an growth inhibition effect on S. mutans.