• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.12
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• pp.2310-2316
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• 2016

We studied the effect of $Co^{60}$ gamma-radiation on the fiber Bragg gratings (FBGs) by irradiation time of UV Krypton fluoride (KrF) excimer laser among grating processing parameters. The FBGs were fabricated in a different UV laser irradiation time at 30, 60, 90, and 120 seconds using the same commercial Ge-doped silica core fiber (SMF-28e). It was exposed to gamma-radiation up to a high dose of 34.3 kGy at the dose rate of 106 Gy/min, and then it was analyzed radiation effects by measuring the radiation-induced change in the temperature sensitivity coefficient and Bragg wavelength shift. According to the experimental results, We confirmed that the UV laser irradiation period for grating inscription has a highly effect on the radiation sensitivity of the FBGs. The radiation-induced Bragg wavelength shift by the change of laser irradiation conditions showed a difference more than about 50 %.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.12
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• pp.4044-4052
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• 1996

Planar images of OH and $O_{2}$ with tunable KrF excimer laser which has a) 0.5 $cm^{-1}$ / linewidth, b) 0.5 nm tuning range, c) 150 mJ pulse energy, and d) 20 ns pulse width are obtained to determine spatial distributions of OH and $O_{2}$ in premixed $C_{3}$H$_{8}$ /O$_{2}$ flame. The technique is based on planar laser induced pre-dissociative fluorescence(PLIPF) in which collisional quenching is almost avoided because of the fast pre-dissociation. Dispersed LIPF spectra of OH and $O_{2}$ are also measured in a flame in order to confirm the excitation of single vibronic state of OH and $O_{2}$, OH and $O_{2}$ are excited on the P$_{2}$(8) line of the $A^{2}$.SIGMA.$^{+}$(v'= 3)-X$^{2}$.PI.(v'||'||'&'||'||'quot;= 0) band and R(17) line of the Schumann-Runge band B$^{3}$.SIGMA.$_{u}$ $^{[-10]}$ (v'= 0)- X$^{3}$.SIGMA.$_{g}$ $^{[-10]}$ (v'||'||'&'||'||'quot;= 6), respectively. Dispersed OH and $O_{2}$ spectra show an excellent agreement with simulated spectrum and previous works done by other group respectively. It is confirmed that OH widely distributed around flame front area than $O_{2}$.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.12
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• pp.1580-1587
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• 2000

Rayleigh scattering and laser induced predissociative fluorescence are employed for capturing two-dimensional images of temperature and species concentration in a laminar nonpremixed flame of a diluted hydrogen jet. Rayleigh scattering cross-sections are experimentally obtained ar 248nm. Dispersed LIPF spectra of OH and O$_2$ are also measured in a flame in order to confirm the excitation of single vibronic state of OH and O$_2$ .OH and O$_2$ are excited on the P$_1$(8) line of the A $^2\Sigma ^+(v^`=3) - X^2\pi (V^"=0)$ band and R(17) line of the Schumann-Runge band B $^3\Sigma _u^-(v^`=0) - X ^3\Sigma _g^-(v^"=6)$, respectively. Fluorescence spectra of OH and Hot O$_2$ are captured and two-dimensional images of the hydrogen flame field are successfully visualized.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.720-725
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• 1995

Bi-substituted gadolinium iron garnet films were deposited on GGG(111) and NGG (111) substrates by irradiating KrF excimer laser onto targets having compositions of $Bi_{x}Gd_{3-x}Fe_{5}O_{12}$ ($2.0{\leq}x{\leq}3.0$) under substrate temperature of $580~620^{\circ}C$. Analysis on structure, composition and angle of Faraday rotation, ${\theta}_{F}$, were carried out. The composition, the structure and the magneto-optical properties of the obtained films were found to be strongly dependent both on the compositions of the targets and on the pressure of oxygen. Before annealing in air, all films showed ${\theta}_{F}{\geq}0$ at ${\lambda}=6328{\AA}$, while several films showed ${\theta}_{F}{\leq}0$ after the annealing. The highest value of Bi-substitution up to x = 1.76 with uniform composition was obtained.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1344-1348
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• 2003

It is generally known to be difficult to etch a surface of a transparent material such as fused silica by conventional laser ablation in which the surface is simply irradiated with a laser beam. A lot of studies have been done to provide a method capable of efficiently etching transparent materials without defects such as cracks. One of the promising methods or the micro-machining of optically transparent materials is laser induced etching. In this study, micro-drilling of fused silica by laser induced wet etching was conducted. KrF excimer and YAG laser were used as light sources. Acetone solution pyrene and ethanol solution of rhodamine were used as etchant.

• Laser Solutions
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• v.17 no.1
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• pp.13-16
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• 2014

Indium Tin Oxide (ITO) has been used widely for transparent conducting thin films. In this work, the feasibility of a laser sintering process to fabricate ITO thin films on flexible substrates is examined. Nanoparticles of ~10 nm were spin coated on a Si wafer and then sintered by a KrF excimer laser. The sintered structure was characterized by scanning electron microscopy. Polycrystalline structures were fabricated by the process without thermally damaging the substrate. The electrical resistivity of the film was reduced to ~ 1/1000 of the initial value. This work demonstrates that nanosecond laser sintering of ITO particles can be a useful tool to fabricate ITO films on various flexible substrates.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.13 no.4
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• pp.157-164
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• 2003

$LaF_{3}$ thin films have been fabricated on Si (100) substrates under the highest possible vacuum condition by pulsed laser deposition (PLD) method. The temperature of the sbustrate varied from $20^{\circ}C$ to $800^{\circ}C$. The films deposited at the higher temperature indicated the sharper peaks in the X-ray diffraction measurement. A highly oriented film was successfully obtained at a substrate temperature of $800^{\circ}C$. The surface observation by the AFM revealed that the many hexagonal structures constructed the film. The XPS analysis revealed that the lacking of F in the film deposited at $600^{\circ}C$ were much more than that in film at $^20{\circ}C$. Adding the adequate amount of $CF_{4}$ gas in the growth chamber can compensate this lacking of F.

• Korean Journal of Optics and Photonics
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• v.11 no.1
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• pp.33-36
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• 2000

KrF excimer laser, which is useful for fabrication of fiber gratings, was irradiated on the PLC-type WDM directional coupler and the transmission wavelength shift was observed as a function of UV exposure time. The effective refractive index change of rectangular silica waveguide was calculated from the wavelength shift measurement and the coupled mode theory. heory.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.10a
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• pp.243-248
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• 1993

New methodology for fiducial alignment is proposed to improve the alignment accuracy in wafer steppers. The positioning error is detected by PSD(Position Sensitive Detector)when 2-dimensional vernier patterns on a reticle on a reticle are projected on the fiducial marks of wafer stage. The width and period of vernier patterns are deter mined to get the highest S/N ratio for the exposure wavelength 248.4nm of KrF excimer laser. This new method has an advantage of higher accuracy and faster alignment over the conventional one.

• Proceedings of the Optical Society of Korea Conference
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• 1991.06a
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• pp.81-87
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• 1991

A design of a four-mirror optical system for submicron lithography using KrF excimer laser beam(λ=248nm) is presented. By using the third order aberration theory, analytic solutions for a telecentric, flat-field, and anastigmatic four-spherical-mirror system (reduction magnification 5$\times$) are found. Aspherization is carried out to the spherical mirror surfaces in order to reduce the residual higher order aberrations and vignetting effect. Finally we obtain a reflection system useful in submicron lithographic application.