• Current Optics and Photonics
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• v.5 no.5
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• pp.506-513
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• 2021

An arrayed diffractive optical element design for the beam-shaping of a multi-array light source is proposed. This is an essential device for recent optical security and face recognition applications. In practice, we devise a DC noise reduction technique featuring high fabrication error tolerance regarding the multi-array light source diffractive optical elements, as a necessary part of the proposed design method. The spherical diverging illumination leads to DC-conjugate noise spreading. The main idea is tested experimentally, and the multi-array light source diffraction pattern is investigated numerically.

• Current Optics and Photonics
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• v.3 no.2
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• pp.172-176
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• 2019

The work reports on the fabrication of an optical planar waveguide in the Nd:CNGG crystal by the 0.4-MeV hydrogen ion implantation with a fluence of $8.0{\times}10^{16}ions/cm^2$. The nuclear energy loss of the implanted hydrogen ions was derived by using SRIM 2013 code. The microscope image of the proton-implanted Nd:CNGG crystal cross section was captured by a metallographic microscope. The transmittance spectra were recorded before and after the ion implantation. The light intensity distribution of the planar waveguide at 632.8 nm was experimentally measured to validate its effect on one dimension confinement. The investigation shows that the proton-implanted Nd:CNGG waveguide is a candidate for an optoelectronic integrated device.

• ETRI Journal
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• v.43 no.5
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• pp.916-922
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• 2021

We calculated the correlation between the doping concentration of the charge layer and the multiplication layer for separate absorption, grading, charge, and multiplication InGaAs/InAlAs avalanche photodiodes (APDs). For this purpose, a predictable program was developed according to the concentration and thickness of the charge layer and the multiplication layer. We also optimized the design, fabrication, and characteristics of an APD for 20 Gbps application. The punch-through voltage and breakdown voltage of the fabricated device were 10 V and 33 V, respectively, and it was confirmed that these almost matched the designed values. The 3-dB bandwidth of the APD was 10.4 GHz, and the bit rate was approximately 20.8 Gbps.

• Proceedings of the Optical Society of Korea Conference
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• 1991.06a
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• pp.1-1
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• 1991

The fabrication of computer components requires a great variety of optical equipment. The patterning of integrated circuits is performed either on step-and-repeat cameras, scanning systems or step-and-repeat systems. The image forming optics used in these machines is quite difficult to design and fabricate. In addtion several layers of patterns must be precisely superposed, and also the illuminators have to provide the final irradiance in the image plane constant to within 1%. Other uses of specialized optical equipment are mass production of chip packages, inspection scanners and laser ablation cameras for polymers. The details of some of these systems will be described with particular ephasis on different optical structures and the use of excimer lasers as light sources.

• Journal of Ceramic Processing Research
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• v.13 no.spc2
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• pp.373-376
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• 2012

Thin films of Ag-SiO2-TiO2 composite oxides with SiO2/TiO2 of 20/80 molar compositions were prepared by the sol-gel method, using tetraethylorthosilicate (TEOS) and titanium isopropoxide (TIP) as precursors. Ag-SiO2-TiO2 films coated on commercial glass substrates have successfully been synthesized using sol-gel method. The Ag-SiO2-TiO2 film with 0.5% Ag-added concentration and 20 mol% SiO2-mixture gives optimal results on crystalline structure, optical property, surface area, and photochromic property. Absorption near the wavelength of the incident light decreased gradually. The reversibility of the two-photon writing process in Ag-SiO2-TiO2 film is clearly seen.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.56.1-56.1
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• 2021

표준우주모형이 예측하는 천체의 성장 역사를 추적하기 위해서는 보통의 밤하늘 밝기보다 약 1000배 어두운 낮은 표면밝기(Low Surface Brightness, LSB) 우주 탐사가 필요하지만, 관측기술의 한계로 아직 LSB 우주는 거의 미지의 세계에 있다고 할 수 있다. 한국천문연구원에서는 LSB 천체 관측에 최적화된 직경 300 mm K-DRIFT Pathfinder 망원경을 개발하였다. LSB 천체는 ~28 mag/arcsec2 보다 어두운 천체로 표면밝기가 매우 낮기 때문에 망원경 내부의 미광(stray light)을 최소화하는 것이 중요하다. 이를 구현하기 위해 K-DRIFT Pathfinder 망원경에는 선형 비점수차가 제거된 비축 자유곡면 삼 반사경 형태를 적용하였다. 본 연구를 통해 가시광 영역에서 선형 비점수차가 제거된 비축 자유곡면 삼 반사 망원경의 설계, 제작 및 측정 가능성을 검증하였다. 본 발표에서는 K-DRIFT Pathfinder 망원경에 적용된 비축 자유곡면 광학면의 가공, 삼 반사 망원경의 조립 및 정렬 결과를 소개한다.

• Current Optics and Photonics
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• v.8 no.1
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• pp.72-79
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• 2024

Recent flat-panel displays have become increasingly complicated to facilitate multiple display functions. In particular, the form of multilayered architectures for next-generation displays makes precise three-dimensional alignment of multiple panels a challenge. In this paper, a diffractive optical alignment marker is proposed to address the problem of three-dimensional alignment of distant dual panels beyond the depth-of-focus of a vision camera. The diffractive marker is effective to analyze the positional correlation of distant dual panels. The possibility of diffractive alignment in multilayer display fabrication is testified with numerical simulation and a proof-of-concept experiment.

• Journal of Magnetics
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• v.11 no.4
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• pp.195-207
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• 2006

The recently published and new results on design and fabrication of magnetophotonic crystals of different dimensionality are surveyed. Coupling of polarized light to 3D photonic crystals based on synthetic opals was studied in the case of low dielectric contrast. Transmissivity of opals was demonstrated to strongly depend on the propagation direction of light and its polarization. It was shown that in a vicinity of the frequency of a single Bragg resonance in a 3D photonic crystal the incident linearly polarized light excites inside the crystal the TE- and TM-eigen modes which passing through the crystal is influenced by Brags diffraction of electromagnetic field from different (hkl) sets of crystallographic planes. We also measured the faraday effect of opals immersed in a magneto-optically active liquid. It was shown that the behavior of the faraday rotation spectrum of the system of the opal sample and magneto-optically active liquid directly interrelates with transmittance anisotropy of the opal sample. The photonic band structure, transmittance and Faraday rotation of the light in three-dimensional magnetophotonic crystals of simple cubic and face centered cubic lattices formed from magneto-optically active spheres where studied by the layer Korringa-Kohn-Rostoker method. We found that a photonic band structure is most significantly altered by the magneto-optical activity of spheres for the high-symmetry directions where the degeneracies between TE and TM polarized modes for the corresponding non-magnetic photonic crystals exist. The significant enhancement of the Faraday rotation appears for these directions in the proximity of the band edges, because of the slowing down of the light. New approaches for one-dimensional magnetophotonic crystals fabrication optimized for the magneto-optical Faraday effect enhancement are proposed and realized. One-dimensional magnetophotonic crystals utilizing the second and the third photonic band gaps optimized for the Faraday effect enhancement have been successfully fabricated. Additionally, magnetophotonic crystals consist of a stack of ferrimagnetic Bi-substituted yttrium-iron garnet layers alternated with dielectric silicon oxide layers of the same optical thickness. High refractive index difference provides the strong spatial localization of the electromagnetic field with the wavelength corresponding to the long-wavelength edge of the photonic band gap.

• Journal of the Korean Society for Heat Treatment
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• v.24 no.2
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• pp.87-91
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• 2011

Single layer Sn doped $In_2O_3$ (ITO) films and ITO 50 nm / Au 10 nm / ITO 40 nm (IAI) multilayer films were prepared with electron beam assisted magnetron sputtering on glass substrates. The effects of the Au interlayer, post-deposition atmosphere annealing and intense electron irradiation on the methanol gas sensitivity were investigated at room temperature. As deposited ITO films did not show any diffraction peaks in the XRD pattern, while the IAI films showed the diffraction peak for $In_2O_3$ (400). In this study, the gas sensitivity of ITO and IAI films increased proportionally with the methanol vapor concentration and an intense electron beam irradiated IAI film shows the higher sensitivity than the others film. From the XRD pattern, it is supposed that increased crystallization promotes the gas sensitivity. This approach is promising in gaining improvement in the performance of IAI gas sensors used for the detection of methanol vapor at room temperature.

• Journal of the Korean Chemical Society
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• v.56 no.6
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• pp.725-730
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• 2012

HEMA (2-hydroxyethyl methacrylate), EGDMA (ethylene glycol dimethacrylate; cross-linker), MMA (methyl methacrylate) and AA (acrylic acid) were copolymerized with ethyl gallate and propyl gallate as additives in the presence of AIBN (2,2'-azobisisobutyronitrile; initiator). The measurement of physical properties of the produced copolymers exhibited that refractive index, water content, visible transmittance, tensile strength, and contact angle were in the range of 1.433-1.435, 38.71-38.99%, 85.4-88.8%, 0.2468-0.2740 kgf and $49.77-36.29^{\circ}$, respectively. The transmittances of the copolymers were measured to be in the range of 49.0-7.4% and 71.0-43.4% for UV-B and UV-A, respectively, indicating that the copolymers have UV-blocking effect. The produced copolymers containing ethyl gallate and propyl gallate satisfied the basic physical properties required for the fabrication of hydrogel contact lenses. The copolymers showed an increase of wettability and UV-blocking effects while having no significant change in water content compared to the gallate-free copolymers.