• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.6
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• pp.63-71
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• 1998

In this paper, we experiment the characteristics of coupling coefficient, gain, diffraction efficiency and dependence of time determined by TWM(Two-Wave Mixing), using Fe-LiNbO$_3$ crystal(doped with 0.015Wt.%). From these results, we proposed to apply for optical memory application. The highest coupling angle of 14。 and maximum coupling coefficient of 6.9$cm^{-1}$ / are obtained at 514.5nm wavelength. Also, maximum diffraction efficiency is 54.13% when intensity ratio and writing beam incident angle are 0.1 and 14o, respectively. After fixing process, diffraction efficiency is 21.4%. As an example, we demonstrated the writing and reconstruct optical data using spatial light modualtor and angular multiplexing in most optimal condition.

• Korean Journal of Optics and Photonics
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• v.4 no.3
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• pp.323-329
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• 1993

In this paper, dependence of the diffraction efficiency upon incident light intensity is studied. The conductivity ratio, which is dependent upon the incident light intensity, changes the static electric field in a crystal. This change of the static electric field modulates the refractive index via linear electro-optic effect. And the change of the refractive index affects the diffraction efficiency. It is found that experimental results with $Fe:LiNbO_3$ crystals are in good agreement with the theory.

• Proceedings of the Optical Society of Korea Conference
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• 2003.07a
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• pp.292-293
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• 2003

반도체 공정에서 위상 소자를 적용하는데 있어, 그 위상항을 ITFA 방법을 적용하여 계산하였고 계산된 위상 소자에 따른 광출력 회절효율을 계산하였다. 이러한 회절 효율의 계산은 출력 평면 내에만 해당되는 것이고, 이외의 영역으로 출력이 소실되는 경우를 고려하지 않았다. 또한, 위상항의 양자화 깊이의 변화에 대하여 입력광이 위상소자를 지난 후의 광출력 효율에 대하여 계산하였다.

• Proceedings of the Optical Society of Korea Conference
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• 2007.07a
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• pp.279-280
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• 2007

• Korean Journal of Optics and Photonics
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• v.21 no.2
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• pp.82-88
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• 2010

Photopolymer is a material for recording three dimensional holograms containing photo information. Photopolymer has been found to be a proper material due to many advantages such as high DE value, easy processing, and low price. Compositions of PVA, monomer, initiater and photosensitizer were determined by previous experiments and the compositions of $SeO_2$ and $TiO_2$ were considered as variable to find out the effects of $TiO_2$ on DE. The DE values were constant for the varying compositions of $TiO_2$ (0.1 mg~1.0 mg). In other words, $TiO_2$ is not directly effective on the DE values. Composition change experiments from $SeO_2$ 0.1 mg, $TiO_2$ 0.9 mg to $SeO_2$ 0.9 mg, $TiO_2$ 0.1 showed a maximum DE value of 73.75% at a component of $SeO_2$ 0.8 mg, $TiO_2$ 0.2 mg. It seemed that regardless of the amount of $TiO_2$, increasing the amount of $SeO_2$ gently increases DE`s. If nano particles are heavily added, transparent films could not be made due to the separation of particles by the solubility decrease. Photopolymer films could be made with high DE values for an extensive angle range if $TiO_2$ additions were kept minimum and $SeO_2$ additions were kept maximum.

• Korean Journal of Optics and Photonics
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• v.16 no.4
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• pp.334-339
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• 2005

We studied the spatial filtering characteristics of a multi-phase hologram optical low-pass filter(HOLF). Using the Monte-Carlo based hologram generation program, we designed holograms whose diffraction patterns are circular shaped 21 beams and calculated the diffraction efficiencies and MTFs. 4-phase HOLF have the same diffraction efficiency as that of 2-phase HOLF. The MTF graphs of the two are also nearly alike. But 8-phase HOLF shows higher efficiency than those previously discussed and has larger MTF values in the low frequency region. 16-phase HOLF has just a little better characteristics than 8-phase. Considering the errors which can arise in the process of making holograms, 8-phase HOLF fits the goal of improving the resolution of spatial filter. We also fabricated 8-phase HOLF and .measured MTF The experimental results agree well with the theoretical expectations.

• Journal of Broadcast Engineering
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• v.24 no.3
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• pp.452-462
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• 2019

A digital hologram, which is one of the next generation visual systems, can be generated and displayed in various formats, and a digital hologram is created in accordance with the characteristics of the system for display. Diffraction efficiency can be used as a measure of the characteristics of digital holograms generaged under various conditions in various display environments. In this paper, diffraction efficiency for computer-generated hologram (CGH) under various conditions was measured. This paper discusses the generation conditions that should be considered in hologram display. We compared each condition by measuring the intensity of the first order diffraction pattern of the fringe generated under the Fresnel condition for the phase hologram. Through this paper, we showed the tend about characteristics of the diffraction efficiency according to object point, reconstruction distance, laser and SLM.

• Korean Journal of Optics and Photonics
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• v.24 no.2
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• pp.53-57
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• 2013

A polarization selective blazed grating employing metal-slit arrays was proposed. Nano-scale metal-slits were applied to the micro-scale blazed grating to give the functionality of polarization selection. Case study was carried out for the proposed structure utilizing numerical FDTD (Finite Difference Time Domain method) simulation. Diffraction efficiency of 77.61% and polarization extinction ratio of 8.99 was achieved with arbitrary parameters and diffraction efficiency of 64.22% and polarization extinction ratio of 81.09 was achieved with other parameters to enhance extinction ratio.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.5
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• pp.123-128
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• 2022

Applying rigorous modal transmission-line theory (MTLT), the properties of resonant diffraction gratings under conical light incidence is investigated. The mode vectors pertinent to resonant diffraction under conical mounting vary less with incident angle than those associated with diffraction gratings in classical mounting. Furthermore, as the evanescent diffracted waves drive the leaky modes responsible for the resonance effects, the conical mounting imbues diffraction gratings with larger angular tolerance than their classical counterparts. Based on these concepts, the angular-spectral and wavelength-spectral performance of resonant diffraction gratings in conical and classical mounts by numerical calculations with spectra found for conical incidence are quantified. These results will be useful in various applications demanding resonant diffraction gratings that are efficient and physically sparse.

• Proceedings of the Korea Crystallographic Association Conference
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• 2003.05a
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• pp.23-23
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• 2003

Cu 단결정과 다결정 Cu 막대(rod)를 시료로 하여 구부린 완전결정(bent perfect crystal, BPC)을 이용한 중성자 단색기의 특성을 평가함으로써 단결정 회절 및 집합조직 측정장치인 4축 단결정 회절장치(FCD)에 BPC 단색기를 적용할 수 있는지 시험하였다. 측정은 한국원자력연구소의 연구용 원자로인 하나로의 571 수평공에 구성된 test station에서 수행하였다. 단색기와 시료 사이의 거리는 3000mm, 시료와 검출기 사이는 600mm, 단색화빔 인출각도(2θ/sub M/)는 44.6°로 고정하여 FCD와 거의 같은 배치를 구현하였다 직사빔의 단면분포와 강도는 저효율 2차원 위치민감형 검출기(2-D PSD)를 이용하여 확인하였다. 이 검출기는 검출면적 90x90㎟, 공간 분해능 1.2mm, 검출효율 약 1%인 저효율 검출기이다. 회절빔은 검출면적 190x190㎟, 검출효율은 1Å에서 60%인 고효율 2-D PSD를 이용하여 측정하였다. Cu 단결정 측정에 사용한 ePC 단색화 결정은 200×40×3.4㎣ 크기의 Si(220) 슬랩이며, 비대칭 기하로 Si(331)면을 사용하여 파장 λ=0.954Å으로 중성자빔을 단색화시켰다. BPC-Si를 구부려 슬랩의 곡률반경을 변화시키면서 단색기-시료-검출기가 평행배치일 때 Cu(200), (220), (400), (420)면의 rocking curve를 측정하여 각 조건에서의 분해능과 강도를 평가하였다. BPC 단색기를 집합조직 측정에 적용할 수 있는지 시험하기 위하여 다결정 Cu 막대(직경 4.5mm, 길이 18mm)를 시료로 선택하였다. 207x30x3.0㎣ 크기의 Si 슬랩을 단색화 결정으로 사용하였다. 이 슬랩은 다양한 결정면을 이용한 특별한 기하를 구현할 수 있도록 Si(111)면에서 10° 벗어난 면을 절단한 것이다. 비대칭 기하로 Si(311)면을 사용하여 파장 λ=1.253Å의 단색화된 중성자빔으로 측정하였다 BPC-Si를 구부려 슬랩의 곡률반경을 변화시키면서 단색기-시료-검출기가 평행파 반평행배치일 때 Cu(111), (200), (220), (311), (331), (420)면의 회절선을 측정하여 각 조건에서 분해능과 강도를 평가하였다.