• Korean Journal of Optics and Photonics
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• v.3 no.4
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• pp.217-221
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• 1992

A micro lens system was designed for the modulator in optical fiber communication. One was the collimating lens which transferred the diffracted beam from optical fiber to the modulator. The other was the coupling lens which connected the modulated collimating beam to the optical fiber. The light source was He-Ne laser beam. The lens would be made of optical glass BK-7. We determined the tolerance of curvature radius, thickness and conic constant.

• Bulletin of the Korean Chemical Society
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• v.34 no.1
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• pp.128-132
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• 2013

L-Arginine semi-oxalate (LASO) single crystal has been grown by solution growth technique at room temperature. The crystal structure and lattice parameters were determined for the grown crystal by single crystal X-ray diffraction studies. Photoluminescence studies confirm the violet fluorescence emission peak at 395 nm. Optical constants like band gap, refractive index, reflectance, extinction coefficient and electric susceptibility were determined from UV-VIS-NIR spectrum. The dielectric constant, dielectric loss and ac conductivity of the compound were calculated at different temperatures and frequencies to analyze the electrical properties. The solid state parameters such as plasma energy, Penn gap, Fermi energy and polarizability were calculated to analyze second harmonic generation (SHG). Nonlinear optical property was discussed to confirm the SHG efficiency of the grown crystal.

• 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.

• Korean Journal of Optics and Photonics
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• v.29 no.1
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• pp.19-27
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• 2018

A change in object distance would generally change the magnification of an optical system. In this paper, we have proposed and designed a double-Gauss optical system with a fixed magnification and image surface regardless of any change in object distance, according to moving the lens groups a little bit to the front and rear of the stop, independently parallel to the direction of the optical axis. By maintaining a constant size of image formation in spite of various object-distance changes in a projection system such as a head-up display (HUD) or head-mounted display (HMD), we can prevent the field of view from changing while focusing in an HUD or HMD. Also, to check precisely the state of the wiring that connects semiconductor chips and IC circuit boards, we can keep the magnification of the optical system constant, even when the object distance changes due to vertical movement along the optical axis of a testing device. Additionally, if we use this double-Gauss optical system as a vision system in the testing process of lots of electronic boards in a manufacturing system, since we can systematically eliminate additional image processing for visual enhancement of image quality, we can dramatically reduce the testing time for a fast test process. Also, the Gaussian bracket method was used to find the moving distance of each group, to achieve the desired specifications and fix magnification and image surface simultaneously. After the initial design, the optimization of the optical system was performed using the Synopsys optical design software.

• Journal of the Optical Society of Korea
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• v.7 no.3
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• pp.197-201
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• 2003

We investigated recording dynamics of a holographic grating in the photorefractive LiNbO$_3$ crystal under the low-intensity condition of recording beams. New expressions for the space-charge field and the recording time constant were obtained by solving the Kukhtarev equations under the global space -charge field, which is induced in the previous process of recording and erasing. Their validity can be confirmed by considering the limit that the period of the grating goes to infinity both theoretically and experimentally. It was found that the new expression for the recording time constant allows us to determine acceptor concentration to be $1.2${\times}$10^{21}m^{-3}$ for pure LiNbO$_3$ crystal and 2.5${\times}$$10^{21}m^{-3}$ for the 0.1 mol% iron doped LiNbO$_3$ crystal from the measured ratio of the recording time constant under the extremely large grating condition, in which the diffusion effect can be neglected, to that under the small grating condition.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.3
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• pp.228-233
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• 2010

We studied the optical characteristics correlated with low dielectric constants of low-k SiOCH thin films through ellipsometry. The low-k SiOCH thin films were prepared by CCP-PECVD method using BTMSM(Bis-trimethylsilylmethane) precursors deposited on p-Si wafer. The Si-O-CHx, Si-O-Si, Si-CHx, CHx and Si-H bonding groups were specified by FTIR spectroscopic spectra, and the groups coupled with the nano-porous structural organic/inorganic hybrid-type of SiOCH thin films which has extremely low dielectric constant close to 2.0. The structural groups includes highly dense pore as well as ions in SiOCH thin films affecting to complex refraction characteristics of single layer on the p-Si wafer. The structural complexity originate the complex refractive constants of the films, and resulted the elliptical polarization of the incident linearly polarized light source of Xe-light source in the range from 190 nm to 2100 nm. Phase difference and amplitude ratio between s wave and p wave propagating through SiOCH thin film was studied. After annealing, the amplitude of p wave was reduced more than s wave, and phase difference between p and s wave was also reduced.

• Electrical & Electronic Materials
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• v.10 no.10
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• pp.1005-1010
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• 1997

ZnS:Mn thin film was made by coevaporation with Electron Beam Evaparation(EBE) method. And structural and optical characteristics of ZnS:Mn thin films were investigated by substrate temperature annealing temperature and dopant Mn. When ZnS:Mn thin film was well deposited with cubic crystalline at substrate temperature of 30$0^{\circ}C$ its surface index was [111] and its lattice constant of a was 5.41$\AA$. Also When ZnA:Mn thin film was well made with hexagonal crystalline at substrate temperature of 30$0^{\circ}C$annealing temperature of 50$0^{\circ}C$and annealing time of 60min its miller indices were (0002) (1011), (1012) and (1120). And its lattice constant of a and c was 3.88$\AA$and 12.41$\AA$ respectively. Finally hexagonal ZnS:Mn thin film with dopant Mn of 0.5wt% had fundamental absorption wavelength of 342nm. And so its energy bandgap was about 3.62eV.

• Proceedings of the Optical Society of Korea Conference
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• 1990.02a
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• pp.162-166
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• 1990

Photoinduced anisotropy (PIA) in amorphous As2S3 (a-As2S3 ) thin film, deposited by vacuum evaporation, is investigated. PIA is induced by linearly polarized Ar+ laser beam (λ=514.5nm) and probed by weak Ar+ laser (λ=514.5nm) and He-Ne laser (λ=632.8nm) beam through the crossed analyzer. Keeping pump beam intensity constantly, rotation of pump beam polarization direction induces reorientation phenomina of anisotropic axis. Introducing directional factor into simplified 3-level system, which is used to analyze photodarkening phenomina, an analytical expression of PIA is derived. Temporal behavior of PIAand its reorientation phenomina are investigated andcompared with theory. In the experiment pump beam intensity is 100mW/$\textrm{cm}^2$ and thickness of a-As2S3 thin film is 3${\mu}{\textrm}{m}$. In those condition, time constant of photoinduced anisotropy obtained by method of least square curve fitting is 4.0$\times$10-2sec-1. The time constant of PIA we obtained is larger than that of photodarkening, 2.8$\times$10-2sec-1.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.10
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• pp.2582-2589
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• 1993

Transient heat transfer characteristics of cooling of a spherical body were investigated in the radiatively active spherical medium. Initially the spherical body and the medium were maintained at their constant temperatures. Then heat transfer begins from spherical body t medium. The heat transfer mode inside the spherical body is just conduction. But heat is transferred by both conduction and radiation inside the medium. All thermodynamic properties were held constant in time. Spherical symmetry is assumed. DOM was adopted to solve RTE. The effect of characteries-tic optical thickness, conduction to radiation parameters, and solid surface emissivity has been studied.

• Advances in materials Research
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• v.2 no.3
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• pp.141-153
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• 2013

Nanocrystalline Barium niobate ($BaNbO_3$) has been synthesized by a novel auto-igniting combustion technique. The X-Ray diffraction studies reveals that $BaNbO_3$ posses a cubic structure with lattice constant $a=4.071{\AA}$. Phase purity and structure of the nano powder are further examined using Fourier-Transform Infrared and Raman spectroscopy. The average particle size of the as prepared nano particles from the Transmission Electron Microscopy is 20 nm. The UV-Vis absorption spectra of the samples are recorded and the calculated average optical band gap is 3.74eV. The sample is sintered at an optimized temperature of $1425^{\circ}C$ for 2h and attained nearly 98% of the theoretical density. The morphology of the sintered pellet is studied with Scanning Electron Microscopy. The dielectric constant and loss factor of a well-sintered $BaNbO_3$ at 5MHz sample is found to be 32.92 and $8.09{\times}10^{-4}$ respectively, at room temperature. The temperature coefficient of dielectric constant was $-179pp/^{\circ}C$. The high dielectric constant, low loss and negative temperature coefficient of dielectric constant makes it a potential candidate for temperature sensitive dielectric applications.