• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 C
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• pp.2020-2021
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• 2004

Distributed optical feedback by gain coupling in V-groove quantum-wire lasers is investigated using InGaAs/AlGaAs active materials grown by metalorganic chemical vapor deposition (MOCVD). In order to avoid grating overgrowth during the fabrication of DFB structures, a newly developed constant MOCVD growth method is employed. Gain anisotropy in emission spectra near Bragg wavelength, resulting from optical feedback along the DFB direction, is clearly observed at room temperature.

• 천문학회보
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• 제39권1호
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• pp.42.2-42.2
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• 2014

We present high-resolution optical spectra of newly selected candidates of intermediate-mass black holes. The sample was selected based on the variability and spectral shape in X-ray. The spectra was taken with Magellan 6.5 m Clay Telescope and cover the rest-frame region 3500-10000A. The high spectral resolution (R~4000) of the spectrum allows us to estimate BH masses of the sources. Interestingly, the majority of the sample appears to have broad emission lines. Using this dataset, we will estimate the BH masses and Eddington ratio in order to understand their physical properties.

• 한국진공학회:학술대회논문집
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• 한국진공학회 1999년도 제17회 학술발표회 논문개요집
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• pp.140-140
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• 1999

Ti/Ni multilayered films (MLF) are ideal for neutron optics particularly in neutron guides and focusing devices. This system also possesses the tendency of amorphization through a solid-state reaction (SSR). This behaviors are closely related to the electronic structures and both magneto-optical (MO) and optical properties of metals depend strongly on their electron energy structures. Mutual inter-diffusion of the Tin and Ni atoms in the MLF caused by a low temperature annealing should decrease the thickness of pure Ni, as well as change the chemical and atomic order in the reactive zone. The application of the MO spectroscopy to the study of SSR in the MLF allows us to obtain an additional information on the changes in the atomic and chemical orders in the interface region. The optical one has no restriction on the magnetic state of the constituent sublayers. Therefore, the changes in magnetic, MO and optical properties of the Ti/Ni MLF due to SSR can be expected. To the best of our knowledge, the MO and optical spectroscopies were not used for this purpose. SSR has been studied in the series of the Ti/Ni MLFs with bilayer periods of 0.65-22.2nm and constant ratio of the Ti to Ni sublayers thickness by using MO and optical spectroscopies as well as an x-ray diffraction. The experimental MO and optical spectra are compared with the computer-simulated spectra, assuming various interface models. The relative changes in the x-ray diffraction spectra and MO properties of the Ti/Ni MLF caused by annealing are bigger for the multilayers with "thick" sublayers, or the SSR with the formation of amorphous alloy takes place mainly in the Ti/Ni multilayers with "thick" sublayers, while in the nominal threshold thickness of the Ni-sublayer for the observation of the equatorial Kerr effect in the as-deposited and annealed Ti/Ni MLFs of about 3.0 and 4.5nm thick is explained by the formation of amorphous alloy during the deposition or the formation of the nonmagnetic alloyed regions between pure components as a result of the SSR. For the case of Ti/Ni MLF the MO approach is more sensitive for the determination of the thickness of the reacted zone, while x-ray diffraction is more useful for structural analyses.structural analyses.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.382-382
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• 2010

$TaO_2$ thin films as gate dielectrics have been proposed to overcome the problems of tunneling current and degradation mobility in achieving a thin equivalent oxide thickness. An extremely thin $SiO_2$ layer is used in order to separate the carrier in MOSFETchannel from the dielectric field fluctuation caused by phonons in the dielectric which decreases the carrier mobility. The electronic and optical properties influenced the device performance to a great extent. The atomic structure of amorphous and crystalline Tantalum oxide ($TaO_2$) gate dielectrics thin film on Si (100) were grown by utilizing atomic layer deposition method was examined using Ta-K edge x-ray absorption spectroscopy. By using X-ray photoelectron spectroscopy and reflection electron energy loss spectroscopy (REELS) the electronic and optical properties was obtained. In this study, the band gap (3.400.1 eV) and the optical properties of $TaO_2$ thin films were obtained from the experimental inelastic scattering cross section of reflection electron energy loss spectroscopy (REELS) spectra. EXAFS spectra show that the ordered bonding of Ta-Ta for c-$TaO_2$ which is not for c-$TaO_2$ thin film. The optical properties' e.g., index refractive (n), extinction coefficient (k) and dielectric function ($\varepsilon$) were obtained from REELS spectra by using QUEELS-$\varepsilon$(k, $\omega$)-REELS software shows good agreement with other results. The energy-dependent behaviors of reflection, absorption or transparency in $TaO_2$ thin films also have been determined from the optical properties.

• Bulletin of the Korean Chemical Society
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• 제24권8호
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• pp.1075-1080
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• 2003

We have investigated femtosecond coherent vibrational motions of Zn(II)-5,15-diphenylporphyrin in toluene using chirp-controlled ultrashort pulses. The oscillatory features superimposed on the temporal profiles of the pump-probe transient absorption signal are affected by the chirping and energy of excitation pulses. Using chirp- and excitation energy-controlled femtosecond pulses, we are able to obtain information on the structural changes between the electronic ground and excited states based on a comparative analysis of the Fouriertransformed frequency-domain spectra retrieved from the oscillatory components with the ground state resonance Raman spectra and normal mode calculations.

• 한국광학회:학술대회논문집
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• 한국광학회 2000년도 제11회 정기총회 및 00년 동계학술발표회 논문집
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• pp.258-259
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• 2000

Quantum Well Disordering (QWD) has drawn a considerable attention in recent years$^{(1-3)}$ due to its wide applicability to optoelectronic devices. QWD allows modification of the shape of QW in selected regions, hence it modifies the subband energies in conduction and valance bands$^{(4)}$ . This leads to changes in optical properties such as band gap, absorption coefficient and refractive index. Thus such disordering in selected areas enables monolithic integration of various optoelectronic devices such as lasers, EA/EO modulators, waveguides and optical amplifiers. In this paper, we investigate the quantum well disordering effects on photoluminescence spectra by using experimental measurements and theoretical analysis$^{(5)}$ . (omitted)

• 한국광학회:학술대회논문집
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• 한국광학회 2009년도 창립 20주년기념 특별학술발표회
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• pp.343-344
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• 2009

Pump wavelength dependence of the gain spectra was investigated by simulating the model of single-pumped fiber optical parametric amplifiers (FOPAs). Conditions for the single-pumped FOPAs having broad bandwidths with relatively large gains were optimized and the gain bandwidth was found to be as large as 146.4 nm when signal power and pump power were 316 nW and 7 W, respectively.

• 한국표면공학회지
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• 제29권5호
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• pp.556-562
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• 1996

Carbon nitride (CN) films were synthesized on silicon substrates by a combined ion-beam and laser-ablation method under various conditions; ion-beam energy and ion-beam current were varied. Raman spectroscopy and spectroscopic ellipsometry (SE) were employed to characterize respectively the structural and the optical properties of the CN films. Raman spectra show that all the CN films are amorphous independent of the ion-beam current and the ion-beam energy. Refractive indices, extinction coefficients and optical band gaps which were determined from the measured SE spectra exhibit a significant dependence on the synthesis conditions. Especially, the decrease of the refractive indices and the shrinkage of the optical band gap is noticeable as the ion-beam current and/or the ion-beam energy increase.

• 한국광학회:학술대회논문집
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• 한국광학회 2009년도 동계학술발표회 논문집
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• pp.205-206
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• 2009

• 한국광학회:학술대회논문집
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• 한국광학회 2009년도 창립 20주년기념 특별학술발표회
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• pp.46-47
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• 2009