• Journal of the Optical Society of Korea
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• v.13 no.1
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• pp.2-7
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• 2009

This paper reviews evolution of the research networks on intense laser science under international and Asian frameworks during 2000 to 2008. The OECD Global Science Forum Steering Committee on Compact, High-Intensity Short-Pulse Lasers led to the establishment of the International Union of Pure and Applied Physics (IUPAP) Working Group: International Committee on Ultrahigh Intensity Lasers (ICUIL) and the Asian Intense Laser Network (AILN) in 2004. Through various activities under AILN such as the Asian Symposium on Intense Laser Science (ASILS), the Asian Summer School on Laser Plasma Acceleration and Radiation, and the High-Order Harmonics Workshops, closer relations are being formed among the scientists and also among the young generations working in intense laser science in the Asian regions.

• Journal of the Optical Society of Korea
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• v.12 no.3
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• pp.178-185
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• 2008

Recent progress in high power lasers enables us to access a regime of high-energy-density and/or ultra-strong fields that was not accessible before, opening up a fundamentally new physical domain which includes laboratory astrophysics and laser nuclear physics. In this article, new applications of high-energy and ultra-intense laser will be reviewed.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.98-99
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• 2012

Deposition of thin films using magnetron sputtering plasmas is a well-developed, classical technology. However, detailed investigations using advanced diagnostics are insufficient in magnetron sputtering, in comparison with plasma-aided dry etching and plasma-enhanced chemical vapor deposition. In this talk, we will show examples of diagnostic works on magnetron sputtering employing metal targets. Diagnostic methods which have fine spatial resolutions are suitable for magnetron sputtering plasmas since they have significant spatial distributions. We are using two-dimensional laser-induced fluorescence spectroscopy, in which the plasma space is illuminated by a tunable laser beam with a planer shape. A charge-coupled device camera with a gated image intensifier is used for taking the picture of the image of laser-induced fluorescence formed on the planer laser beam. The picture of laser-induced fluorescence directly represents the two-dimensional distribution of the atom density probed by the tunable laser beam, when an intense laser with a relatively wide line-width is used. When a weak laser beam with a relatively narrow linewidth is used, the laser-induced fluorescence represents the density distribution of atoms which feel the laser wavelength to be resonant via the Doppler shift corresponding to their velocities. In this case, we can obtain the velocity distribution function of atoms by scanning the wavelength of the laser beam around the line center.

• Journal of the Korea Institute of Military Science and Technology
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• v.15 no.2
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• pp.201-207
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• 2012

Pulsed lasers at the 613 nm and 1064 nm wavelengths on nanoseconds have been utilized to characterize the damage on Si photodiode exposed to intense illumination. Morphological damages and structural changes at sites on the photodiode irradiated during microseconds of laser pulses were analyzed by FE-SEM images and XRD patterns, respectively. The removal of oxide coating, ripple, melting marks, ridges, and crater on photodiodes were definitely observed in order of increasing the pulse intensities generated above the damage threshold. Then, the degradation in photosensitivity of the Si photodiode irradiated by high power density pulses was measured as a function of laser irradiation time at the various wavelengths. The free charge carrier and thermal diffusion mechanisms could have been invoked to characterize the damage. The relative photosensitivity data calculated using the thermal diffusion model proposed in this paper have been compared with the experimental data irradiated above the damage threshold.

• Current Applied Physics
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• v.18 no.11
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• pp.1230-1234
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• 2018

We report a new method of measuring the non-radiative recombination rate in bulk Silicon. Synchrotron timeresolved x-ray scattering (TRXS) combines femtometer spatial sensitivity with nanosecond time resolution to record the temporal evolution of a crystal lattice following intense ultrafast laser excitation. Modeling this data requires an Auger recombination time that is considerably slower than previous measurements, which were made at lower laser intensities while probing only a relatively shallow surface depth. We attribute this difference to an enhanced Coulomb interaction that has been predicted to occur in bulk materials with high densities of photoexcited charge carriers.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.7
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• pp.1026-1033
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• 2009

Fine ceramics have high strength, excellent wear resistance, chemical stability and high strength at high temperature and are receiving attention in various fields such as construction, engineering, aerospace and marine science. Finish machining process is required to obtain precise ceramics components because sintering process necessary for obtaining high strength and high quality ceramics reduces the dimensions of components and precision of shape. But high strength and brittleness of ceramics materials cause difficulty in processing. So a process for obtaining wanted dimensions is studying using high temperature which makes ceramics softened and thermal affected recently. Laser beam is a very useful optical device for these kinds of processes. Laser process such as laser cutting, laser machining, laser heat treatment and laser-assisted machining(LAM) is researching to manufacture practical ceramics components using intense laser source which can cause local softening and damage of workpiece. In this paper, microstructural and mechanical properties of silicon nitride heated are studied as a basic study for researching of ceramics process by laser beam. The surface variation of HIP and SSN-silicon nitride was analyzed with SEM and EDS. A processing at $1,300^{\circ}C$ or above causes N element to combine into $N_2$ gas and the gas busts from surface. These phenomena make bloat, craters and heat defects on the surface of silicon nitride. Also, oxygen content is largely increased to oxidize the surface and it causes changing of phases and reducing of hardness of surface.

• Medical Lasers
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• v.9 no.1
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• pp.12-24
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• 2020

Human fibroblast-derived multi-peptide factors (MPFs) have been used during treatments with energy-delivering modalities to enhance energy-induced tissue reactions. Human fibroblast-derived MPFs, which include a range of growth factors and chemoattractive factors, activate and recruit fibroblasts and endothelial cells, as well as promote extracellular matrix deposition, all of which are crucial to wound repair. Interestingly, fibroblasts from different species or anatomical sites exhibit distinct transcriptional properties with high heterogeneity. In addition, the patterns of MPF secretion can differ under a range of experimental conditions. Therefore, the use of allogeneic fibroblasts and proper cultivation thereof are necessary to obtain MPFs that can enhance the epithelial-mesenchymal interactions during wound repair. Moreover, energy-delivering devices should be selected according to evidence demonstrating their therapeutic efficacy and safety on a pathological skin condition and the major target skin layers. This paper reviewed the histologic patterns of post-treatment tissue reactions elicited by several energy sources, including non-ablative and ablative fractional lasers, intense focused ultrasound, non-invasive and invasive radiofrequency, picosecond-domain lasers, and argon and nitrogen plasma. The possible role of the immediate application of human fibroblast-derived MPFs during wound repair was proposed.

• Journal of Yeungnam Medical Science
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• v.40 no.4
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• pp.423-425
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• 2023

Porokeratosis ptychotropica is an uncommon form of porokeratosis, which was initially described in 1995. It is clinically characterized by symmetrical reddish to brown-colored hyperkeratotic, verrucous, or psoriasiform plaques on the perianal and gluteal regions. The lesions tend to integrate and expand centrally, with small peripheral satellite lesions. Early skin biopsy and appropriate diagnosis are essential because malignant change occurs in 7.5% of porokeratotic lesions. Conventional treatment options include topical steroid, retinoid, imiquimod, 5-fluorouracil, isotretinoin, excimer laser, photodynamic therapy, intralesional steroid or bleomycin injection, cryotherapy, carbon dioxide (CO₂) laser, and dermatome and excision, but none seem to achieve complete clearance. A 68-year-old woman presented with diffuse hyperkeratotic scaly lichenoid plaques on the buttocks that had persisted for several years. A skin biopsy of the buttocks revealed multiple cornoid lamellae and intense hyperkeratosis. There were some dyskeratotic cells beneath the cornoid lamellae and the granular layer was absent. Porokeratosis ptychotropica was diagnosed based on the characteristic clinical appearance and typical histopathological manifestations. She was treated with a CO₂ laser in one session and topical application of urea and imiquimod cream for 1 month. The lesions slightly improved at the 1-month follow-up. We herein present a rare case of porokeratosis ptychotropica.

• Journal of the Optical Society of Korea
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• v.12 no.1
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• pp.57-61
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• 2008

We investigated the laser pulse-width dependence of dense plasmas confined within the magnetic length of $In_{0.2}Ga_{0.8}As$/GaAs multiple quantum wells under high magnetic fields up to 31 T. To fully fill the Landau levels of effectively zero-dimensional system, we used intense femtosecond (fs) laser pulses to create carrier densities near $10^{13}/cm^2$. The observed photoluminescence showed a characteristic of superfluorescence, above critical magnetic field when being excited by pulses shorter than coherence buildup time.

• Korean Journal of Optics and Photonics
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• v.18 no.4
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• pp.270-273
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• 2007

We have investigated the output characteristics of the 946 nm Nd:YAG laser which is longitudinally pumped by a fiber coupled laser diode. The temperature of a Nd:YAG crystal mount was kept constant by a controller with thermoelectric cooler. As a result, we measured more intense output at a low temperature, and then the maximum output power was measured to be 870 mW when the pumping power and the temperature were 9.95 W and $5^{\circ}C$, respectively. It appeared that output was decreased above 10 W pump power because of the thermal effects in gain medium.