• Proceedings of the Optical Society of Korea Conference
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• 2005.02a
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• pp.10-11
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• 2005

• Proceedings of the Korean Society of Potoscience Conference
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• spring
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• pp.36-37
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• 1999

• Optical Science and Technology
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• v.2 no.1
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• pp.75-76
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• 1998

• Journal of Mechanical Science and Technology
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• v.19 no.6
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• pp.1378-1389
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• 2005

This work provides the fundamental knowledge of energy transport characteristics during very short-pulse laser heating of semiconductors from a microscopic viewpoint. Based on the self-consistent hydrodynamic equations, in-situ interactions between carriers, optical phonons, and acoustic phonons are simulated to figure out energy transport mechanism during ultrafast pulse laser heating of a silicon substrate through the detailed information on the time and spatial evolutions of each temperature for carriers, longitudinal optical (LO) phonons, acoustic phonons. It is found that nonequilibrium between LO phonons and acoustic phonons should be considered for ultrafast pulse laser heating problem, two-peak structures become apparently present for the subpicosecond pulses because of the Auger heating. A substantial increase in carrier temperature is observed for lasers with a few picosecond pulse duration, whereas the temperature rise of acoustic and phonon temperatures is relatively small with decreasing laser pulse widths. A slight lagging behavior is observed due to the differences in relaxation times and heat capacities between two different phonons. Moreover, the laser fluence has a significant effect on the decaying rate of the Auger recombination.

• Journal of IKEEE
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• v.5 no.2 s.9
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• pp.201-210
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• 2001

Wavelength and repetition-rate tunable optical pulse-trains for ultrafast optical time- and wavelength division multiplexing are generated from a semiconductor fiber ring laser by optical injection mode-locking. The pulse trains show the pulse with of ${\sim}10$ ps and the wavelength tuning of wider than 30 nm at various repetition-rates of 10 GHz, 20 GHz, 30 GHz and 40 GHz, respectively.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.209-210
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• 2000

The energy transfer from photoexcited polyvinylcarbazole (PVK) chromophores with a bandgap of 3.7 eV as a donor to fluorophores of poly(dihexylfluorenevinylene) (PDHFV) or poly(dihexylfluorenedihexoxyphenylenevinylene) (PDHFHPV) as an acceptor in bilayered specimens should be carried out since the spectral overlap pairs fulfills the requirement for the $F{\"{o}}rster-type$ condition. However, the energy transfer rate from the chromophores with a wider bandgap to the fluorophores with a narrower bandgap is proved to be strongly dependent on the lifetime ratio between the excitons.

• Bulletin of the Korean Chemical Society
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• v.26 no.1
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• pp.19-31
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• 2005

During the last decade, the exploration of nanoscale device and circuitry based on molecules has gained increasing interest. In parallel with this, considerable effort is being devoted to the development of molecular photonic/electronic materials based on various porphyrin arrays. This involves light as an input/output signal and excitation energy migration as a mechanism for signal transmission. Absorption of a photon at the light collector end of the porphyrin array yields the excited state, which migrates among the intervening pigments until reaching the emitter, whereupon another photon is emitted. As a consequence, it is relevant to understand the excitation energy transfer (EET) processes occurring in various forms of porphyrin arrays for the applications as artificial light harvesting arrays and molecular photonic/electronic wires. Since the excitonic (dipole) and electronic (conjugation) couplings between the adjacent porphyrin moieties in porphyrin arrays govern the EET processes, we have characterized the EET rates of various forms of multiporphyrin arrays (linear, cyclic, and box) based on various time-resolved spectroscopic measurements. We believe that our observations provide a platform for further development of molecular photonic/electronic materials based on porphyrin arrays.

• Journal of the Optical Society of Korea
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• v.20 no.4
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• pp.470-475
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• 2016

In this paper, the effects of filter parameters on a supercontinuum-based all-optical thresholder are experimentally investigated. By tuning the filter parameters, the power transfer function and power transmission function are tailored. The experimental results show that a thresholder with short center wavelength has a better power function, and the slope in the middle level of the thresholder increases with increasing bandwidth. Through tuning the filter parameters, the thresholder can achieve a steplike power transfer function for optical thresholding, and a steplike power transmission function for optical self-switching. This makes the supercontinuum-based thresholder more flexible, and allows customization of performance to meet different demands in various applications.

• Journal of the Korean Magnetics Society
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• v.21 no.6
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• pp.204-207
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• 2011

We developed a time-resolved magneto-optical Kerr effect microscope system to investigate ultrafast magnetization dynamics. Based on the pump-probe method, 0.1-ps time resolution was achieved by use of a fs Ti:Sapphire laser. The magnetization dynamics was then measured on Pt/Co/Pt thin films with various Co thicknesses. All the samples exhibited ultrafast demagnetization within a few ps by direct heating of pump laser. Some thicker samples showed precessional motion of magnetization, from which the Gilbert damping constant was determined based on the Landau-Lifshitz-Gilbert equation.

• Journal of IKEEE
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• v.12 no.4
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• pp.234-238
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• 2008

We demonstrate a simple method to generate a stable 40 GHz pulse train at 1550 nm by spectral filtering of a 10 GHz mode.locked pulse source using a fiber Fabry-Perot interferometer (FFPI). A high finesse FFPI with a 40 GHz free spectral range blocks successfully unwanted spectral components of a 10 GHz pulse source and passes only 40 GHz spaced spectral lines ensuring pulse repetition-frequency quadruplication of the input pulses.