• Journal of the Optical Society of Korea
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• v.17 no.1
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• pp.1-4
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• 2013

For the conventionally polished fused silica substrate, an around 100 nm depth redeposition polishing layer was formed on the top of surface. Polishing compounds, densely embedded in the redeposition polishing layer were the dominant factor that limited the laser induced damage threshold (LIDT) of transmission elements in nanosecond laser systems. Chemical etching, super-precise polishing and ion beam etching were employed in different ways to eliminate these absorbers from the substrate. After that, Antireflection (AR) coatings were deposited on these substrates in the same batch and then tested by 1064 nm nano-pulse laser. It was found that among these techniques only the ion beam etching method, which can effectively remove the polishing compound and did not induce extra absorbers during the disposal process, can successfully improve the LIDT of AR coatings.

• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1307-1310
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• 1995

During measurement of atomic hydrogen in a silane plasma using two-photon excited laser induced fluoresecence, laser-induced dissociation of the gas was observed. This was investigated untill conditions for the input laser fluence were determined where the effect was negligible. A measurement of the atomic hydrogen distribution was then performed within the limits of these conditions. Absolute density determinations showed atomic hydrogen densities of around $3{\times}10^{17}m^{-3}$.

• Electrical & Electronic Materials
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• v.9 no.3
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• pp.240-245
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• 1996

Non-ozone layer destructive Chlorofluorocarbon(CFC) altematives(CHCIF$_{2}$ and $C_{2}$H$_{2}$F$_{4}$) have been initially used for laser-induced thenrmochemical etching of GaAs. High etching rate up to 188.mu.m/sec and an aspect ratio of 2.7 have been achieved by a single scan of laser beam, respectively. The etching rate at constant ambient gas pressure was found to saturate for beam power. The chemical compositions of the reaction products deposited on the etched groove were measured by Auger electron microscopy(AES). Etched profile, depth and width were observed by scanning electron microscope(SEM).

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.6
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• pp.625-631
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• 2015

The hardness of surface treated magnesium alloy was evaluated using laser induced breakdown spectroscopy. The surface of the specimen was hardened mechanically, and the hardness profiles were measured using a traditional measurement technique. A laser beam was irradiated to generate a plasma, and the peaks of the components of the specimen were analyzed. A wavelength of 333.66 nm and 293.65 nm were selected as the atomic and ionic peaks, respectively. The ratios of the ionic peak to the atomic peak were obtained so as to compare the hardness profile. As the depth increased, the ratio decreased. These results are in good agreement with the previous hardness measurement results. It can be considered that this technique could be applied for remote and time-efficient hardness measurement.

• Journal of the Korean Vacuum Society
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• v.9 no.1
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• pp.76-80
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• 2000

CF & $CF_2$ radicals in a $C_4F_8$ inductively coupled plasma were observed with laser induced fluorescence. 251.9nm UV laser was used for the $CF_2$ excitation and 265.3nm UV emitted light for the detection which has the maximum intensity among many induced fluorescence lights. In the case of CF radical detection, 232.9nm UV laser was used for the excitation and 247.6nm for the detection. $CF_2$ radical density increased toward substrate, while CF radical had its maximum at about 10nm away from the substrate. The atomic fluorine density which was studied by the actinometry increased as the position moves away from the substrate. This phenomena was thought to have a close relation with the polymer growth on the wafer. When the bias voltage increased, $CF_2$ , CF radicals decreased while the atomic fluorine increased tio some extent and then decreased, which was thought to be due to the change in the ionization and dissociation.

• Bulletin of the Korean Chemical Society
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• v.14 no.5
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• pp.610-614
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• 1993

Laser induced impedance changes in hollow cathode lamps containing sputtered metal atoms have been employed to measure the spectroscopic properties of metal. This technique, known as optogalvanic spectroscopy, has been shown to be a powerful and inexpensive technique for the investigation of atomic and molecular species. Characteristic optogalvanic signals from hollow cathode lamps (HCL) made of different metal species and induced with a pulsed dye laser were observed, and the dependence of the optogalvanic signal on the discharge current and wavelength of laser was measured. Based on the results obtained, the mechanisms involved in evoking the optogalvanic signals were consisted of single-photon absorption, multi-photon absorption, and photoionization. Moreover the current dependence of the optogalvanic signal indicates that the optogalvanic technique could be one of the most sensitive optical methods of detecting atomic species.

• Biomedical Science Letters
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• v.10 no.3
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• pp.231-235
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• 2004

This study was investigated the effects of the lower power He-Ne IR laser treatment on the changes of blood biochemical components in the rat liver damaged by the carbon tetrachloride (CCl₄). The twenty one Sprague-Dawley adult male rats weights (260±18.6 g) were designed to the three groups: one control group and two experimental groups, the experimental groups were divided into the CCl₄-treated groups and the laser therapy group (CCl₄+ Laser). The experimental groups were injected twice with CCl₄(1.0 ml/kg body weight) intraperitoneal for two days. Each group was sacrificed after two weeks irradiated with the lower power He-Ne IR laser for ten minutes per every day. The activity of alanine aminotransferase (ALT), lactic dehydrogenase (LDH), alkaline phosphatase (ALP) and the concentration of serum glucose treated with He-Ne IR laser groups was significantly decreased to the conrtol (treated with carbon CCl₄) group. The activity of aspartate aminotransferase (AST) was decreased in the laser group but not significantly, the concentration of the serum cholesterol in the laser group was significantly increased comparing with the control and case control groups. In conclusion, the effect of the lower power He-Ne IR laser treatment is believed to be a possible protective effects for CCl₄ induced acute hepatotoxicity in rats.

• Laser Solutions
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• v.14 no.1
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• pp.1-5
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• 2011

Photo-induced gratings m flexible PDMS (polydimethly siloxane) film are directly written by a high-intensity femtosecond (130fs) Ti: Sapphire laser (${\lambda}_p$ = 800nm). The refractive index modifications with $4\;{\mu}m$ diameters were photo-induced after the femtosecond irradiation with peak intensities of more than $1{\times}10^{11}W/cm^2$. The graded refractive index profile was fabricated to be a symmetric around the center of the point at which femtosecond laser by controlling both laser power and focused depth. The change on refractive index in the laser-modified regions was estimated to be approximately $10^{-3}$. The internal flexible symmetric diffraction gratings in PDMS film was successfully fabricated using a femtosecond laser.

• Journal of the Microelectronics and Packaging Society
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• v.7 no.2
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• pp.43-46
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• 2000

Nd:YAG laser of 355 nm wavelength, which amounts to 3.5 eV, produced by a harmonic generator was used to create Ag metallic particles as seeds for nucleation in photosensitive glass containing $Ag^+$ and $Ce^{3+}$ . The pulse widths and frequency of the laser were 8ns and 10 Hz, respectively. For crystalline growth, heat-treatment following laser irradiation was carried out at $570^{\circ}C$ for 1h. Then, the $LiAlSi_3O^8$ crystal phase appeared in the laser irradiated lithium aluminum silicate glass. We present the effect of laser-induced nucleation compared with spontaneous nucleation by heat treatment fur crystallization in the glass.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2000.04a
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• pp.112-117
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• 2000

Nd:YAG laser of 355nm wavelength, which amounts to 3.5eV, produced by a harmonic generator was used to create Ag metallic particles as seeds for nucleation in photosensitive glass containing Ag+ and Ce3+. The pulse widths and frequency of the laser were 8ns and 10Hz, respectively. For crystalline growth, heat-treatment following laser irradiation was carried out at $570^{\circ}C$ fur 1h. Then, the LiAlSi3O8. crystal phase appeared in the laser irradiated lithium aluminum silicate glass. We present the effect of laser-induced nucleation compared with spontaneous nucleation by heat treatment for crystallization in the glass.