• Title/Summary/Keyword: Nd:yag laser

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Quasi-phase matched optical parametric oscillators using periodically poled $KNbO_3$ crystals (주기적으로 분극 반전된 $KNbO_3$를 이용한 준위상 정합 광 매개 진동자)

  • Lee Gwang Jo;Kim Jung Hyeon;Im Min Ho;O Hyeon Ho;Lee Don Hui;Yun Chun Seop
    • Proceedings of the Optical Society of Korea Conference
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    • 2003.02a
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    • pp.230-231
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    • 2003
  • $KNbO_3$is one of the best materials for efficient nonlinear frequency conversion, due to its large nonlinear optical coefficient ($d_{33}$ = 20.6 pm/V), wide transparency range (0.4 ~ 5 $\mu$m) and freedom from photorefractive effects. Quasi-phase-matched second harmonic generation using periodically poled $KNbO_3$ (PPKN) crystals has been reported. Here we report on fabrication of PPKN and demonstration of a pulsed optical param etric oscillator (QPM OPO) pumped by an Nd:YAG laser. (omitted)

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Macroscopic Behavior and Atomization Characteristics of Bio-diesel Fuels (바이오 디젤 연료의 분무 거동 및 미립화 특성)

  • Suh, Hyun-Kyu;Park, Sung-Wook;Kwon, Sang-Il;Lee, Chang-Sik
    • Transactions of the Korean Society of Automotive Engineers
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    • v.12 no.6
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    • pp.23-29
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    • 2004
  • This work was conducted to figure out the atomization characteristics of three types of bio-diesel fuels using a common-rail injection system. The process of spray development was visualized by using a spray visualization system composed of a Nd:YAG laser and an ICCD camera, The spray tip penetrations were analyzed based on the frozen images from the spray visualization system. On the other hand, the microscopic atomization characteristics such as the distributions of SMD and axial mean velocity were measured by using a phase Doppler particle analyzer system, It is revealed that the sprays of the bio-diesel fuels have larger SMD than that of diesel fuel mainly due to high viscosity of bio-diesel. Different characteristics of bio-diesel fuels were also measured in spray tip penetrations according to the fuels and mixing ration.

4D-PTV(Dynamic 3D-PTV) Measurement on an Impinged Jet (4차원 입자영상유속계(다이나믹 3차원 입자영상유속계)에 의한 충돌분류측정)

  • Doh, Deog-Hee;Hwang, Tae-Gyu;Cho, Yong-Beom;Pyeon, Yong-Beom;Koji, Okamoto
    • Proceedings of the KSME Conference
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    • 2004.04a
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    • pp.1767-1771
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    • 2004
  • A 4D-PTV system was constructed. The measurement system consists of three high-speed high-definition cameras, Nd-Yag laser(10mJ, 2000fps) and a host computer. The GA-3D-PTV algorithm was used to extract three-dimensional velocity vectors in the measurement volume. A horizontal impinged jet flow was measured with the constructed system. The Reynolds number is about 40,000. Spatial temporal evolution of the jet flow was examined in detail and physical properties such as spatial distributions of vorticity and turbulent kinetic energy were obtained with the constructed system.

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Analysis of Spray Characteristic for 3-Component Mixed Fuel (3 성분 혼합연료의 분무특성 해명)

  • Myong, Kwang-Jae
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.33 no.8
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    • pp.589-595
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    • 2009
  • The instability wave formed near nozzle region grows to vortex with large scale in downstream region of spray. It plays an important role in the fuel-air mixing, combustion process and engine exhaust emissions in direct injection diesel engine. The objective of this study is to analyze effect of variant parameters (injection pressure, ambient gas density, etc.) and fuel properties on spray instability near nozzle region. Spray structure near nozzle region was investigated using a magnification photograph. A pulsed Nd-YAG laser was used as a light source, and image was taken by CCD camera. The following conclusions are drawn from this experimental analysis. In low ambient density, the effect of fuel properties on spray instability near nozzle region is dominant. In high ambient density, the effect of ambient gas on spray instability near nozzle region is dominant. High jet velocity has strong influence on spray instability.

An Experimental Study on the Flow Characteristics in Highly Viscous Liquid by Multi-Nozzle Bubbling (고점성 액체 내부에서의 다중 노즐 버블링에 의한 유동특성에 대한 실험적 연구)

  • Kim, Hyun-Dong;Ryu, Seung-Gyu;Kim, Kyung-Chun
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.31 no.2 s.257
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    • pp.195-201
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    • 2007
  • A visualization study of flow characteristics in a mixer using multi-nozzle bubbling was performed. The mixer is filed with liquid glycerin (dynamic viscosity = $1000mPa{\cdot}s\;at\;25^{\circ}C$) and convective mixing is induced by air bubbles generated from 9 orifices installed on the bottom of the mixer. To visualize the flow field, PIV (Particle Image Velocimetry) system consisting of 532nm Nd:YAG laser, $2k{\times}2k$ CCD camera and synchronizer is adopted. The bubbles generated with uniform size and frequency form bubble stream and bubble streams rise vertically without interaction between bubble streams. Mixing efficiency is affected by the height of bubbler and the effective height of bubbler is 20nm from the bottom of the mixer.

Effect of laser irradiation and optical properties of Ce3+ doped glass (Ce3+ doped glass의 광학적 특성 및 레이저 조사의 영향)

  • 이용수;황태순;강원호
    • Proceedings of the International Microelectronics And Packaging Society Conference
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    • 2002.05a
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    • pp.177-179
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    • 2002
  • 본 연구는 Ag와 Ce이 함유된 유리를 용융법에 의해 제조하였으며, 355nm Nd:YAG 펄스 레이저를 조사하였을 때의 광학적 특성과 열처리과정에서 발생하는 결정화의 변화과정에 대해 평가하였다. Ce이 함유된 유리는 환원 분위기에서 제조되었으며, Optical Absorption을 통하여 Ce$^{3+}$ 이온이 존재하는 유리의 흡수대역을 관찰하고자 하였다. Photo Luminescence(PL) 측정을 통해 Ce$^{3+}$ 이 존재하고 있음을 확인하였으며, Ce$^{3+}$ 이온의 5d$\longrightarrow$4f 전이를 관찰하였다. 이와같이 Ce$^{3+}$ 가 함유된 유리는 레이저를 조사하였을 경우 PL의 강도가 저하됨을 확인하였다. 열처리과정에서 발생하는 결정화현상을 고찰하기 위해 열분석을 실시하였으며, 레이저조사된 유리에서 최대결정화온도가 감소함을 관찰하였다.

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Optical Coating for SHG device by RF Sputtering Method (RF 스퍼터링방법에 의한 제2고조파소자의 광학박막 제작)

  • Kim, Yong-Hun;Lee, Seong-Guk;Ma, Dong-Jun;Han, Jae-Yong;Park, Seong-Su;Lee, Sang-Hak
    • Korean Journal of Materials Research
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    • v.6 no.6
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    • pp.636-643
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    • 1996
  • 공진기형 제 2고조파소자(SHG)는 레이저 빔의 에너지 밀도가 높아 고내구성 박막이 필요하다. 본 연구에서는 광학박막 재료로 고융점 산화물인 ZrO2, TiO2, SiO2를 사용하였다. 반응성 스퍼터링 방법으로 제작한 ZrO2, TiO2, SiO2 박막을 XRD, SAM을 사용하여 분석하였고, 박막의 광학적 특성을 평가하였다. SHG 소자의 KTP 및 Nd:YAG 결정의 반사방지막(A/R 코팅)구성은 ZrO2와 SiO2를 사용하여 컴퓨터로 계산하였는데 기본파인 1064nm와 제 2고조파인 532nm에서 각각 0.1%, 0.5%이하의 반사율을 갖도록 하였다. 또한 고반사막(H/R 코팅)의 경우 1064nm에서 99.9%의 반사율을 갖도록 TiO2와 SiO2로 디자인하였다. 제작한 광학박막의 광학적 특성, 레이저 내구성(laser damage threshold), 온습도 안정성 실험 등을 통해 광학박막을 평가하였다.

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Characterization of Al:ZnO thin films deposited at different substrate temperatures (기판 온도변화에 따른 Al-ZnO 박막의 특성)

  • No, I.J.;Shin, P.K.;Lee, C.;Kim, Y.H.;Ji, S.H.;Lim, Y.C.;Chung, M.Y.
    • Proceedings of the KIEE Conference
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    • 2007.07a
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    • pp.242-243
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    • 2007
  • Highly transparent conducting aluminum-doped zinc oxide (AZO) thin films were deposited on Corning glass substrate using an Nd:YAG pulsed laser deposition technology. AZO thin films deposited with 650nm thickness showed the best electrical properties of the electrical resistivity of $4.6{\times}10^{-4}[{\Omega}{\cdot}cm]$, a carrier concentration of $9.3{\times}10^{20}[cm^{-3}]$, and a carrier mobility of $31[cm^2/V{\cdot}s]$. Besides, the optical transmittance spectra in visible region (200-800nm) of AZO thin films show an high average transmittance over 90%.

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Characterization of Al:ZnO thin films deposited at different oxygen pressure (산소 분위기압의 변화에 따른 Al:ZnO 박막의 특성)

  • No, I.J.;Kim, Il;Shin, P.K.;Song, J.H.;Kim, Y.W.;Kim, C.Y.;Jeung, Y.S.
    • Proceedings of the KIEE Conference
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    • 2007.07a
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    • pp.1349-1350
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    • 2007
  • Epitaxial thin films of aluminum-doped zinc oxide (AZO) have been deposited on commercial corning glass using an Nd:YAG pulsed laser deposition technology. The structural, electrical and optical properties of these films were investigated as a function of oxygen pressure. The experimental results show that the electrical resistivity of films deposited at 5 mTorr with substrate temperature of $300^{\circ}C$ were $4.633{\times}10^{-4}$. The average transmission of AZO thin films in the visible range were over 90%.

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Flow Visualization and PIV Measurement of Multiphase Flow in Highty Viscous Liquid (고점성 유체 내부에서의 다상유동장 가시화 및 PIV 측정)

  • Kim, Hyun-Dong;Ryu, Seung-Gyu;Kim, Kyung-Chun
    • 한국가시화정보학회:학술대회논문집
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    • 2006.12a
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    • pp.48-54
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    • 2006
  • A visualization study of flow characteristics in a mixer using multi-nozzle bubbling was performed. The mixer is filled with liquid glycerin (dynamic viscosity = $1000mPa{\cdot}$ s at $25^{\circ}C$) and convective mixing is induced by air bubbles generated from 9 orifices installed on the bottom of the mixer. To visualize the flow field, PIV (Particle Image Velocimetry) system consisting of 532nm Nd:YAG laser, $2k\times2k$ CCD camera and synchronizer is adopted. The bubbles generated with uniform size and frequency form bubble stream, and bubble streams rise vertically without interaction between bubble streams. Mixing efficiency is affected by the height of bubbler and the effective height of bubbler is 20mm from the bottom of the mixer.

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