• 한국광학회:학술대회논문집
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• 한국광학회 2000년도 하계학술발표회
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• pp.220-221
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• 2000

가공용 레이저로는 $CO_2$, 루비, Nd:YAG, 아르곤 이온 레이저 등이 이용되고 있으며, 이중 펄스형 Nd:YAG 레이저는 $CO_2$ 레이저와 함께 레이저 가공에 널리 사용되는 고체 레이저로서 마킹(making), 트리밍(trimming), 리페어링(repairing) 등의 정밀 가공 분야에서 많은 실용화가 이루어져 왔다.$^{(1)}$ $CO_2$ 레이저의 경우 매질가스로 $CO_2$, $N_2$, He 등을 사용해야하므로 취급 및 유지보수가 불편하지만, 열전도율이 높고, 기계적 광학적으로 안정된 Nd:YAG 레이저는 램프에 의한 광 여기 방식이므로 유지보수가 쉽다. 또한 광 출력의 제어가 용이하며, 광파이버에 의한 빔 전송이 가능하여 산업기술 및 의료 분야에서의 적용이 더욱 더 확대되고 있다.$^{(2)}$ (중략)

• 한국광학회:학술대회논문집
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• 한국광학회 2000년도 하계학술발표회
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• pp.246-247
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• 2000

Yb$^{3+}$ 이온은 InGaAs LD 및 Ti:sapphire 레이저로 펌핑할 수 있는 940 nm에서의 흡수대를 가지고 있고, 1.03 $mu extrm{m}$의 형광방출 특성을 가지고 있으며, 지금까지 알려진 1 $\mu\textrm{m}$ 파장대의 레이저 활성이온 중에서 가장 적게 열을 발생하는 특성을 가지고 있음이 알려져 최근에는 Yb$^{3+}$ 이온을 첨가한 여러 가지 레이저 매질이 연구되고 있다.[1] 그 중에서도 Yb$^{3+}$ ion doped yttrium aluminum garnet (Yb:YAG) 단결정은 충분하게 넓은 흡수선폭, 좋은 열광학적 특성, 고출력 작동을 하게 하는 stokes shift, 그리고 LD에 의한 펌핑을 가능하게 하는 940 nm 영역에서의 흡수 및 긴 여기시간을 가진 이상적인 매질로 알려져 있다.[2] 이러한 특성으로 인해 Yb:YAG 단결정은 femtosecond 레이저 등 각종 레이저 시스템의 소형화[3]를 가져왔으며, 레이저 결정의 양산 가능성 및 레이저 기기의 소형화에 따르는 시스템의 가격 감소가 가능하므로 Yb:YAG microchip 레이저는 향후 고출력 레이저 기기 산업의 중추가 될 것으로 기대된다. (중략)

• 한국광학회지
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• 제12권2호
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• pp.98-102
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• 2001

포화흡수체$Cr^{4+}:YAG$와 유기염료 박막을 사용한 $1.06{\mu}m$ Nd:YAG 공진기에서 수동 큐스위칭 동작시 나타나는 포화흡수체의 포화특성을 분석하였다. 정상모드와 수동 큐스위칭 레이저의 문턱에너지 차이로 광손실을 측정하여 큐스위칭 동작에서 나타나는 포화흡수체의 포화투과도와 불포화 기저상태 밀도수를 분석하였다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 제14회 신호처리 합동 학술대회 논문집
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• pp.777-783
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• 2001

This paper is mainly concerned with the state of the practical developments of a constants PWM bridge type resonants DC-DC suitable converter for Nd:YAG Laser with a Microprocessor. (PIC16C54 & 8051) The use of IGBT power supply with feedback control of flashLamp currents imparts a advantages to Nd:YAG Laser for materials processing. these include the alility to tailor the pulseshape and modify pulse parameters on a pulse- by pulse basis. And Correct choice of pulseshape can enhance the repeatability of the process. as higher power IGBT became available, act ive pulseforming power supplies will find greater user in deep hole drilling machine By Using certain control tecniques, utililized in designing Pic16c54 from Microchip technology and Intel 8051, also Mornitoring from Microsoft Visual Basic 5, And it allowed us to designed and fabricate ahigh repel it ion rate and high power(HRHP) pulsed Nd:YAG laser system, As a result of that, the current pulsewidth could be contort led 200s to 350s(step 50s) , and the pulse repetition rate could be adjusted 500pps to 1150pps. In addition, in the case of one laser head consisting of a Nd:YAG laser rod and two flashlamps , the maximum laser output of 240w was produced at the condition of 350s and 1150pps, and that of about 480w was generated at the same condition when two laser heads were arranged in cascade.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 A
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• pp.514-517
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• 1996

Zero current switching(ZCS) series resonant converter is used to control laser power density in a pulsed Nd:YAG laser power supply. The high power and high repetition rate paused Nd:YAG laser is designed and fabricated to control current pulse width and pulse repetition rate in the double elliptical laser oscillator. In order to find out operational characteristics of pulsed Nd:YAG laser, the electrical properties of driving power supply and laser output power are investigated and experimented by changing of the current pulse width from 200uS to 350uS(step 50uS) and pulse repetition rate range of 500pps(pulse per second) to 1150pps. From that result, we obtaind maximum efficiency of 1.83% and maximum laser output or 220W at the condition of 350 uS and 1150pps with one Nd:YAG rod), and obtained that of more than 400W with two laser head connecting series.

• Journal of Oral Medicine and Pain
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• 제23권1호
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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.

• Journal of Oral Medicine and Pain
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• 제25권1호
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• pp.129-144
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• 2000

The purpose of this study was to examine dentin surface changes of extracted sound third molar specimens which were etched with 10% maleic acid and irradiated at $7-140J/cm^2$ with $CO_2$ and at $156-280J/cm^2$ with Nd:YAG laser. The results were as follows. 1. Dentin surfaces etched with 10% maleic acid and then irradiated at below of $42J/cm^2$ with $CO_2$ laser showed the retentive morphology for resin restoration. 2. Dentin surfaces irradiated at below of $42J/cm^2$ with $CO_2$ laser showed the increased acid-resistance. 3. Dentin surfaces irradiated at $218-280J/cm^2$ with Nd:YAG laser showed the retentive morphology. 4. Dentin surfaces irradiated at $218-280J/cm^2$ with Nd:YAG laser and etched 10% maleic acid and then $218-280J/cm^2$ with Nd:YAG laser showed the increased acid-resistance.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.910-915
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• 2004

The objective of this study is to investigate the influence of process parameters, such as power of laser, travel speed of laser and material thickness, on the practical cutting region and the kerfwidth for the case of cutting of CSP 1N sheet using high power Nd:YAG laser with continuous wave(CW). In order to find the practical cutting region and the relationship between process parameters on the kerfwidth, several laser cutting experiments are carried out. The effective heat input is introduced to consider the influence of power and travel speed of laser on the kerfwidth together. From the results of experiments, the allowable cutting region and the relationship between the effective heat input and kerfwidth for the case of cutting of CSP 1N sheet using high power CW Nd:YAG laser have been obtained to improve the dimensional accuracy of the cut area.

• 한국정밀공학회지
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• 제20권7호
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• pp.44-55
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• 2003

The Nd:YAG laser process is known to have high speed and deep penetration capability to become one of the most advanced welding technologies. This paper describes the machining characteristics of SM45C carbon steel welding by use of an Nd:YAG laser. In spite of its good mechanical characteristics, SM45C carbon steel has a high carbon contents and suffers a limitation in the industrial application due to the poor welding properties. The major process parameters studied in the present laser welding experiment were position of focus, travel speed and laser power. Optical microscope and SEM were used to investigate the microstructures of the welded zone. The experimental results showed that penetration depth of the welding process increases with laser power. Both the microstructural investigation and the theoretical calculations indicated that materials undergoes a very high heating and cooling cycle during welding process. It was also found that the austenite nucleation takes place at the initial stage and the completion temperature of austenite transformation is much higher than in the case of the arc welding.

• 한국정밀공학회지
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• 제29권10호
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• pp.1078-1088
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• 2012

In this paper, we present research experimental results about the different thickness T-joint welding of the high power continuous wave(CW) Nd:YAG laser for the secondary battery of a vehicle. Although the conventional method used for the secondary battery is a argon TIG welding, we utilize a laser welding to improve Tungsten Inert Gas(TIG) welding's weakness. The laser, which has a couple of advantage such as aspect ratio, low Heat Affected Zone(HAZ), good welding quality and fast productivity utilized in this work is a CW Nd:YAG laser. In order to observe laser welding sections, we used a optical microscope. Through the analysis of the metallographic, hardness, aspect ratio, and heat input, we obtained the desired data in condition of 1800 W laser beam power and 1.8 m/min and 2.0 m/min laser beam travel speeds. In order to compare electric resistances of the argon TIG welding and laser welding, we made an actual battery and the electric resistance of the laser welding is reduced by 40~45% comparing with the argon TIG welding.