• Title/Summary/Keyword: 굴절 및 회절

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Measurement of Refractive Index Profile of Optical Fiber Using the Diffraction Phase Microscope (회절위상현미경을 이용한 광섬유의 굴절률 프로파일 측정)

  • Jafar-Fard, Mohammad R.;Moon, Sucbei
    • Korean Journal of Optics and Photonics
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    • v.23 no.4
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    • pp.135-142
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    • 2012
  • We have developed a measurement method of the refractive index profile of an optical fiber by using diffraction phase microscopy. In the microscope system, the reference light was extracted directly from the probe light that passed through the sample by means of pinhole filtering with a diffraction grating. The spatial interference pattern produced by the probe light and the reference light was processed to generate the phase image of the sample fiber. The index profile was obtained by the inverse Abel transform of the phase profile. In order to remove the background phase that originated from the index difference between the cladding and the surrounding medium, the background phase was calculated from the phase data of the cladding to make a core phase profile that can be directly transformed to the index profile of the core without the full phase image that includes the entire cladding part.

불규칙파의 굴절ㆍ회절 수치모형

  • 채장원;정신택
    • Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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    • 1992.08a
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    • pp.83-83
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    • 1992
  • 풍파가 수심이 불규칙하고 조류 및 해류 등의 흐름이 존재하는 연안역을 전파해 갈 때 파고 및 파향이 굴절ㆍ회절 및 천수, 에너지 감쇠 효과 등에 의해 크게 변형된다. 이러한 현상은 연안역의 파랑변형 계산 및 퇴적물이동현상 분석에 매우 중요하다. 불규칙파의 스펙트럼 형태와 에너지의 방향 분산 정도에 따라 단순 규칙파 모델과의 계산치가 50-100%에 이르기도 한다.(중략)

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방조제 주변 설계파의 추정

  • 유동훈;원유승
    • Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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    • 1996.10a
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    • pp.38-41
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    • 1996
  • 심해에서 풍파의 형성은 주로 바람에 의한 마찰력과 파와 파간의 상호간섭 그리고 white capping 현상등에 의한 1차 에너지 손실에 의하여 이루어지며, 파의 변이는 주로 이상의 세 가지 물리현상에 좌우된다. 이러한 심해역에서의 파의 변이를 해석할 때 굴절, 회절 및 마찰손실 등에 의한 천해역 현상은 무시할 수 있으며 풍파의 형성은 주로 바람 조건에 좌우된다. 그러나 파도가 일단 심해역에서 천해역으로 들어오게 되면, 천수, 굴절, 회절 및 마찰손실 등에 의하여 급격하게 변이한다. (중략)

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Numerical Solution of the Mild Slope Equation Using Conjugate Gradient Method (반복기법을 사용한 완경사방정식의 수치해석)

  • 윤종태
    • Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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    • 1993.07a
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    • pp.26-28
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    • 1993
  • 해안구조물의 설치나 해안환경 문제를 다룰때 가장 필수적인 것이 그 지역에서의 정확한 파랑자료이다. 파랑은 천해로 전파해 옴에 따라 수심 및 지형변화로 인한 회절 및 굴절을 겪으면서 변하게 되므로 복잡한 지형을 가진 해안에서의 정확한 파랑계산은 용이한 일이 아니다. 이러한 파랑변형에 대한 연구는 Berkhoff(1972)가 완경사방정식을 발표한 후 큰 진전을 보이게되는데 이로 인해 종래 개별적으로 다루던 굴절과 회절을 함께 취급할 수 있게 되고 파향선이 교차할때 생기는 불합리한 에너지의 집중(caustics)을 해결할 수 있게 되었다. (중략)

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Numerical Analysis of Nonlinear Effect of Wave on Refraction and Diffraction (파의 굴절 및 회절에 미치는 비선형 효과에 대한 수치해석)

  • 이정규;이종인
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.2 no.1
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    • pp.51-57
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    • 1990
  • Based on second-order Stokes wave and parabolic approximation, a refraction-diffraction model for linear and nonlinear waves is developed. With the assumption that the water depth is slowly varying, the model equation describes the forward scattered wavefield. The parabolic approximation equations account for the combined effects of refraction and diffraction, while the influences of bottom friction, current and wind have been neglected. The model is tested against laboratory experiments for the case of submerged circular shoal, when both refraction and diffraction are equally significant. Based on Boussinesq equations, the parabolic approximation eq. is applied to the propagation of shallow water waves. In the case without currents, the forward diffraction of Cnoidal waves by a straight breakwater is studied numerically. The formation of stem waves along the breakwater and the relation between the stem waves and the incident wave characteristics are discussed. Numerical experiments are carried out using different bottom slopes and different angles of incidence.

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Influences of Pretreatment Procedures, and Refractive and Absorptive Indices in Grain Size Analysis of Sandy Samples by Laser Diffraction Grain Size Analyzer (레이저 회절 입도분석기를 이용한 사질 시료의 입도분석에 있어서 전처리 및 굴절율과 흡수율의 영향)

  • Yoon, Soon-Ock;Hwang, Sangill;Park, Chung-Sun
    • Journal of the Korean Geographical Society
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    • v.48 no.6
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    • pp.819-836
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    • 2013
  • This study aims to compare the inf luences of pretreatment procedures, and refractive and absorptive indices in grain size analysis of sandy samples collected from Sagot Beach, Baengnyeong Island by laser diffraction grain size analyzer, and propose the proper procedure and method in grain size analysis of sandy samples. The analyzed samples do not indicate large differences by the three pretreatment procedures applied in this study. However, the organic matters should be removed by hydrogen peroxide, because the samples without hydrogen peroxide pretreatments show differences from the samples with hydrogen peroxide pretreatments. The results with a refractive index of 1.3 and absorptive index less than 0.01 also indicate differences from those with other indices. Compared to the differences in fine samples, these differences are not significant and thus, it can be concluded that the results in grain size analysis of sandy samples are not greatly influenced by the refractive and absorptive indices. However, other indices out of the ranges should be applied.

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Fabrication of $Fe:LiNbO_3$ Waveguides and Their Photorefractive Properties ($Fe:LiNbO_3$ 도파로의 제작 및 광굴절 특성)

  • 강기형
    • Korean Journal of Optics and Photonics
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    • v.4 no.1
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    • pp.108-113
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    • 1993
  • In this paper, we study the photorefractive properties of Fe indiffused $LiNbO_3$ waveguides. Comparing the photorefractive properties of $Fe:LiNbO_3$ with those of $LiNbO_3$, we confirm the increase of the diffraction efficiency and the sensitivity by Fe doping. Also for the photorefractive properties of $Fe:LiNbO_3$ waveguides with different ambient gases, the diffaction efficiency and the sensitivity of $Fe:LiNbO_3$ indifused in pure argon gases are the highest and its decay time is the shortest. Therefore, it is recommended that pure argon gases be used in Fe indiffusion process for good optical switches with photorefractive effect.

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Diffractive characteristics of the photorefractive gratings in $LiNbO_3$:MgO ($LiNbO_3$:MgO 결정에서 광굴절 격자의 회절 특성)

  • 이재철;장지웅;김준태;신승호
    • Korean Journal of Optics and Photonics
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    • v.10 no.5
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    • pp.391-395
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    • 1999
  • We present the measurement of the diffraction efficiency and response time of the photorefractive grating recorded in $LiNbO_3$ photorefractive crystal doped with 4%-mole MgO. Two laser sources were used in the experiments; frequency-doubled Q-switched Nd:YAG laser ($\lambda$=532 nm) and cw Ar-ion laser ($\lambda$=514.5 nm). The same optical geometry was also used in both experiments in order to maintain the experimental consistency. Using the two-wave mixing scheme in both experiments we measured the maximum diffraction efficiency in the range of beam intensity of 1.6~100 W/ $\textrm{cm}^2$, and the response times for both cases of recording and erasing. Two sets of results obtained from the experiments are compared and analyzed.

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