• 한국광학회지
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• 제4권4호
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• pp.442-446
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• 1993

T$i^{3+}$: sapphire 레이저를 선형 xenon 섬광관을 이용하여 펌핑시켜 그 발진 특성을 조사하였다. Ti: sapphire 레이저에 적합한 섬광관 펌핑 조건을 찾기 위하여 섬광관에 인가되는 펄스의 시간폭이 각각 10${\mu}s$, 45${\mu}s$, 65${\mu}s$인 세 가지의 방전 회로에 대하여 실험하였다. 섬광관에서 방출된 빛 중에서 Ti: sapphire 의 흡수대보다 짧은 파장의 빛을 Ti: sapphire 의 흡수대와 일치하는 파장의 빛으로 바꾸어 주기 위하여 그 형광 스펙트럼이 Ti: sapphire 의 흡수대와 잘 일치하는 색소 LD-490을 형광에 의한 에너지 전환제로 선택하였다. LD-490의 농도의 변화에 따른 레이저의 출력변화를 측정한 결과 농도가 1.0${\times}10^{-3}$mol/l 일때의 레이저 출력이 가장 높았다. LD-490의 농도를 1.0${\times}10^{-3}$mol/l로 하였을 경우 펌핑광의 펄스폭을 10, 45, 65$\mu\textrm{s}$로 증가시킬 경우 기울기 효율은 각각 2.3%, 1.5%, 1.1%로 감소하였다. 문지방 에너지는 각각 22, 65, 95 J로 증가하였다.

• 한국광학회지
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• 제15권3호
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• pp.263-267
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• 2004

Ti:sapphire 레이저로 펌핑하는 연속발진 Nd:YAG 레이저의 출력 특성과 Cr$^{4+}$:YAG 결정을 포화 흡수체로 이용하는 수동형 Q-switching된 Nd:YAG 레이저의 평균 출력, 펄스폭 및 반복률 등의 특성을 조사하였다. 그 결과 Nd:YAG 결정에 입사되는 Ti:sapphire 레이저의 펌핑 출력이 850 ㎽일 때, 연속 발진 Nd:YAG 레이저의 출력이 450 ㎽로 측정되어 출력 기울기 효율이 약 56%로 계산되었다. 또한, 초기 투과율이 90%인 Cr$^{4+}$:YAG 결정을 이용하여 수동형 Q-switching된 Nd:YAG 레이저 출력이 200㎽로 측정되었고, 이때의 펄스 반복률 및 펄스폭은 각각 23.8 KHz 및 17.0 ns로 측정되었다.되었다.

• 한국정밀공학회지
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• 제29권3호
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• pp.247-252
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• 2012

This study has been focused on application of ELID mirror-surface grinding technology for manufacturing single crystal optic sapphire. Single crystal sapphire is a superior material with optic properties of high performance as light transmission, thermal conductivity, hardness and so on. Mirror-surface machining technology is necessary to use sapphire as optic parts. The ELID grinding system has been set up for machining of the sapphire material. According to the ELID experimental results, it shows that the surface of sapphire can be eliminated by metal bonded wheel with micron abrasives and the surface roughness of 60nmRa can be gotten using grinding wheel of 2,000 mesh in 4.5um, depth of cut. In this study, the chemical experiments after ELID grinding also has been conducted to check chemical reaction between workpiece and grinding wheel on ELID grinding process. It shows that the chemical reaction has not happened as the results of the chemical experiments.

• Tribology and Lubricants
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• 제34권6호
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• pp.209-216
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• 2018

Sapphire is a substrate material that is widely used in optical and electronic devices. However, the processing of sapphire into a substrate takes a long time owing to its high hardness and chemical inertness. In order to process the sapphire ingot into a substrate, ingot growth, multiwire sawing, lapping, and polishing are required. The lap grinding process using pellets is known as one of the ways to improve the efficiency of sapphire substrate processing. The lap grinding process ensures high processing efficiency while utilizing two-body abrasion, unlike the lapping process which utilizes three-body abrasion by particles. However, the lap grinding process has a high material removal rate (MRR), while its weakness is in obtaining the required surface roughness for the final polishing process. In this study, we examine the effects of free abrasives in lap grinding on the material removal characteristics of sapphire substrate. Before conducting the lap grinding experiments, it was confirmed that the addition of free abrasives changed the friction force through the pin-on-disk wear test. The MRR and roughness reduction rate are experimentally studied to verify the effects of free abrasive concentration on deionized water. The addition of free abrasives (colloidal silica) in the lap grinding process can improve surface roughness by three-body abrasion along with two-body abrasion by diamond grits.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2003년도 춘계학술대회 논문집
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• pp.422-427
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• 2003

Sapphire have been ground by the ultra-precision surface grinder having a glass -ceramic spindle of extremely-low thermal expansion with various cup-type resinoid-bonded diamond wheels of #400-#3000 in grain size. Sapphire can be ground in the ductile mode. And also, the surface roughness and grinding conditions has been clarified. The smooth surface of Sapphire less than 1nm RMS, 1nm Ra can be obtained by the ultra-precision grinding without any polishing Process.

• Tribology and Lubricants
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• 제32권2호
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• pp.56-60
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• 2016

Sapphire has a high hardness and strength and chemical stability as a superior material. It is used mainly as a material for a semiconductor as well as LED. Recently, the cover glass industry used by a sapphire is getting a lot of attention. The sapphire substrate is manufactured through ingot sawing, lapping, diamond mechanical polishing (DMP) and chemical mechanical polishing (CMP) process. DMP is an important process to ensure the surface quality of several nm for CMP process as well as to determine the final form accuracy of the substrate. In DMP process, the material removal is achieved by using the mechanical energy of the relative motion to each other in the state that the diamond slurry is disposed between the sapphire substrate and the polishing platen. The polishing platen is one of the most important factors that determine the material removal characteristics in DMP. Especially, it is known that the geometric characteristics of the polishing platen affects the material removal amount and its distribution. This paper investigated the material removal characteristics and the effects of the polishing platen groove in sapphire DMP. The experiments were preliminarily carried out to evaluate the sapphire material removal characteristics according to process parameters such as pressure, relative velocity and so on. In the experiment, the monitoring apparatus was applied to analyze process phenomena in accordance with the processing conditions. From the experimental results, the correlation was analyzed among process parameters, polishing phenomena and the material removal characteristics. The material removal equation based on phenomenological factors could be derived. And the experiment was followed to investigate the effects of platen groove on material removal characteristics.

• 한국광학회:학술대회논문집
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• 한국광학회 1991년도 광학 및 양자전자학 워크샵
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• pp.71-75
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• 1991

Ti-Sapphire 레이저는 광대역 특성 때문에 최근 색소레이저의 대체 레이저로써 활발히 연구되고 있다. 본연구에서는 고분해 분광학의 광원으로 이용하기 위해 설계 제작한 단일 종모드로 동작하는 Ti:Sapphire 레이저의 특성에 대해 논한다.

• 한국광학회:학술대회논문집
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• 한국광학회 1990년도 제5회 파동 및 레이저 학술발표회 5th Conference on Waves and lasers 논문집 - 한국광학회
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• pp.115-120
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• 1990

The spectroscopic properties of Cr3+-doped sapphire and Ti3+-doped sapphire fibers are reported. Tensile stress produces blue shifts of the R lines and changes in their radiative lifetimes and integrated intensities which can be correlated to stress-induced changes of the crystal-field parameters in a Cr3+-doped sapphire fiber. A net red shift of the zero phonon fluorescence line of 2Eg state and a decrease of the splittings of 2T2g state with uniaxial stress are observed in a Ti3+-doped sapphire. In excitation spectra the two peaks from the 2Eg state are shifted to the blue with different rates. The changes are attributed to the stress-induced changes of crystal field and Jahn-Teller effect.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1995년도 추계학술대회 논문집
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• pp.148-151
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• 1995

Excimer laser has been used to fabricate superconducting YBa$_2$Cu$_3$O$\sub$7-x/(YBCO) thin films on various substrates. An XeCl excimer laser with an wavelength of 308 nm was used to deposit both buffer layer and superconducting thin film on sapphire substrate. The characterizations of the interface between thin film and substrate were performed. The interfacial properties of thin films on buffered sapphire and on bare sapphire were compared. With a 20 nm PrBa$_2$Cu$_3$O$\sub$7-x/(PBCO) buffer layer, no diffusion layer was observed between film and substrate while the diffusion layer with about 30 nm thickness was observed between film and sapphire without buffer layer.

• 한국전기전자재료학회논문지
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• 제24권1호
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• pp.7-11
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• 2011

Sapphire substrate was patterned by a selective chemical wet etching technique, and GaN/InGaN structures were grown on this substrate by MOVPE (Metal Organic Vapor Phase Epitaxy). The surface of grown GaN on patterned sapphire substrate (PSS) has good morphology and uniformity. The patterned sapphire substrate LED showed better light output than conventional LED that improvement 50%. We think these results come from enhancement of internal quantum efficiency by decrease of threading dislocation and increase of light extraction efficiency. Also these LED showed more uniform emission distribution in angle than conventional LED.