• Journal of the Korean Physical Society
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• v.73 no.11
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• pp.1663-1674
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• 2018

We propose the Poynting vector analysis of the air mode in a top-emitting organic light-emitting diode (OLED) by combining the transfer matrix method and dipole source term. The spatial profiles of the time-averaged optical power flow of the air mode are calculated inside and outside the multilayer structure of the OLED with respect to the thickness of the semi-transparent top cathode and capping layer (CPL). We elucidate how the micro-cavity effect controlled by the thickness variation of the semi-transparent top cathode or CPL affects the internal optical power and absorption loss inside the OLED multilayer and the external optical power coupled into the air. When the calculated absorption loss and external power obtained by the proposed Poynting vector and currently-used point dipole models are compared, two calculation results are identical, which demonstrates the validity of the two models.

• Journal of Korean Society for Atmospheric Environment
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• v.17 no.5
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• pp.375-384
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• 2001

Optical remote sensing techniques are particularly advantageous over the conventional fixed point methods because with these methods large-area monitoring can be possible and sample preparation difficulties are avoidable. Instruments based on the differential optical absorption spectroscopy (DOAS) technique are widely used for monitoring air pollutants in urban areas in recent years. In this study, $O_3$, SO$_2$, NO$_2$, and VOCs (benzene, toluene, xylene, and styrene) are measured continuously at Sihwa industrial area using a DOAS from February to November. 1999. Intercomparison between the DOAS method and the conventional methods (filed point samplers for $O_3$, NO$_2$, and SO$_2$, and adsorbent sampling methods and gas chromatography for VOCs) are performed simultaneously at the same site. The time series of the DOAS data and that of fixed point method show good match at the view point of the tendency, but the absolute concentration values of these two methods differ quite a lot from each other; correlation coefficients shows 0.78 for $O_3$and 0.97 for SO$_2$. However, the results of VOCs measurements are not quite satisfactory ; the spectral interference with $O_2$and $O_3$appears to be the major cause of the errors for VOCs .

• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1398-1400
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• 1998

The physical properties of the LB films with merocyanine dyes have been published and attract attention due to the possibility of molecular structure control. The evaluation of the thin films was focused for the purpose of molecular structure control. The molecular structure in the case of the thin films with dyes can be examine by optical absorption spectra measurements. In the case of optical absorption spectra of the LB films by the heat treatment at $70^{\circ}C$ in the air, both of the shifted absorption bands decay and a monomer absorption peak of about 530 nm appears instead. And, the formation and dissociation of J-aggregates, anisotropic behavior was no longer observed in the heat treated merocyanine dyes LB films. In the results, study of the merocyanine dyes LB films using optical absorption spectra would an interesting problem of absorption peak shifts and mixed components.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.34.2-34.2
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• 2009

The silver sulphide (Ag2S) thin films have been chemically deposited from an alkaline medium (pH 8 to 10) by using a silver nitrate and thiourea as a Ag and S ion precursor sources. Ethylene Damine tetraacetic acid (EDTA) was used as a complexing agent. The effect of annealing atmosphere such as Ar, N2+H2S and O2 on the structural, morphological and optical properties of Ag2S thin films has been studied. The annealed films were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and optical absorption techniques for the structural, morphological, and optical properties, respectively. XRD studies reveal that the as-deposited thin films are polycrystalline with monoclinic crystal structure, is converted in to silver oxide after air annealing. The surface morphology study shows that grains are uniformly distributed over the entire surface of the substrate. Optical absorption study shows the as-deposited Ag2S thin films with band gap energy of 0.92eV and after air annealing it is found to be 2.25 eV corresponding to silver oxide thin films.

• Korean Journal of Materials Research
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• v.14 no.2
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• pp.152-156
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• 2004

We have studied the effective optical absorption power of Si solar cell with $SiO_2$-antireflection layer based on a mathematical modelling of AM(air mass)1 spectrum and Si refractive index in the wavelength range(0.4 $\mu\textrm{m}\leq$λ$\leq$$0.97\mu\textrm{m}$). The effective optical absorption power obtained from the theoretical calculation was 450 and 520 W/$\m^2$ for the Si solar cells with $SiO_2$-antireflection layer of 500$\AA$ and 1000$\AA$, respectively. The optimum thickness of $SiO_2$-antireflection layer showing the minimum reflection loss was about 1000$\AA$ in the computer simulation. Two kinds of Si solar cells named EBS(500$\AA$) and EBS(l000$\AA$) were fabricated to evaluate the effect of $SiO_2$-antireflection layer thickness on the optical absorption. The epitaxial base Si cell with $SiO_2$-antireflection layer of 1000$\AA$ [EBS(l000$\AA$)] showed the output power improvement of about 15% upon the EBS(500$\AA$) cell due to larger absorption of effective optical power under illumination of AM1, 1 sun.

• Journal of the Optical Society of Korea
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• v.19 no.1
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• pp.1-6
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• 2015

We investigate the propagation characteristics of a pulse laser in a time-of-flight laser range finder (TOF-LRF) system with variations in atmospheric conditions, such as temperature, pressure, relative humidity, and the concentration of $CO_2$. The measurement error of distance related with the group velocity change in the TOF-LRF system is analyzed by considering the refractive index of the standard atmosphere with variations in atmospheric conditions. The dependence of the pulse width broadening induced by chromatic dispersion of the standard atmosphere on the operating wavelength and the initial pulse width of the light sources is discussed. The transmission of air with variations in the relative humidity or the concentration of $CO_2$ is analyzed by using different values of absorption coefficients depending on the operation wavelength of the light source in the TOF-LRF system.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.352-353
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• 2007

The spectrum for $0_{\circ}$, $90_{\circ}$-polarized light coincides with the spectrum for non-polarized light and also with the spectrum was observed in the LB film deposited using a fresh solution. And, the formation and dissociation of J-aggregates, anisotropic behavior was no longer observed in the heat treated merocyanine dyes LB films. But, in the optical absorption spectra of same LB films by UV irradiation at room temperature, their were observed only dissociation of J-aggregates, that is decrease of absorbance peak without change spectral shape. On the other hand, in the case of optical absorption spectra of the LB films by the heat treatment at $70^{\circ}C$ in the air, both of the shifted absorption bands decay and a monomer absorption peak of about 530 nm appears instead.

• Korean Journal of Remote Sensing
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• v.22 no.2
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• pp.141-151
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• 2006

UV-visible absorption measurement techniques using several horizone viewing directions in addition to the traditional zenith-sky pointing have been recently developed in ground-based remote sensing of atmospheric constituents. The spatial distribution of various trace gases close to the instrument can be derived by combing several viewing directions. Multi-axis differential optical absorption spectroscopy (MAX-DOAS) technique, one of the remote sensing techniques for air quality measurements, uses the scattered sunlight as a light source and measures it at various elevation angles (corresponding to the viewing directions) by sequential scanning with a stepper motor. A MAX-DOAS system developed by GIST/ADEMRC has been applied to measuring trace gases in urban air and plumes of the volcano and fossil fuel power plant in January, May, and October 2004, respectively. MAX-DOAS spectra were analyzed to identify and quantify $SO_2,\;NO_2,\;BrO,\;and\;O_4$ (based on Slant Column Densities, SCD) in the urban air, volcanic plume, and fossil fuel power plant utilizing theirs specific structured absorption features in the UV-visible region. Vertical scan through the multiple elevation angles was performed at different directions perpendicular to the plume dispersion to retrieve cross-sectional distribution of $SO_2\;or\;NO_2$ in the plumes of the volcano and fossil fuel power plant. Based on the estimated cross sections of the plumes the mixing ratios were estimated to 580 $SO_2$ ppbv in the volcanic Plume, and 337 $NO_2\;and\;227\;SO_2$ ppbv in the plume of the fossil fuel power plant, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.182-185
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• 2001

The functionlized dendrimer containing 48 azobenzene was synthesized. Many isolated featureless domains were explicitly observed even at the air-water interface. Also, these monolayers were representatively observed, showing the change of surface pressure with irradiation time and wavelength. In AFM images. the larger domains irregularly shaped structures on the top while the smaller ones were free from such defects. In the optical absorption spectra of the LB films by UV irradiation and heat treatment, only photoisomerization of the G4-48Az monolayers was observed, a decrease of absorbance peak without change of the spectral shape. This suggests that optical behavior and morphological change are affected by the functional group and the symmetric chain.

• Current Optics and Photonics
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• v.7 no.2
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• pp.136-146
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• 2023

Based on calculations using the macroscopic Maxwell's equations with mesoscopic boundary conditions, light absorption by a layered metal-insulator-metal (MIM) metamaterial system embedded in three different environments is investigated. Increasing the top metal thickness shifts the broad absorption band to lower dielectric-constant regions and longer wavelengths, for either TM or TE waves. Boosting the dielectric-layer thickness redshifts the broadband absorption to regions of larger dielectric constant. In air, for the dielectric-constant range of 0.86-3.40, the absorption of the system exceeds 98% across 680-1,033 nm. In seawater with optimized dielectric constant, ≥94% light absorption over 400-1,200 nm can be achieved; particularly in the wavelength range of 480-960 nm and dielectric-constant range of 0.82-3.50, the absorption is greater than 98%. In an environment with even higher refractive index (1.74), ≥98% light absorption over 400-1,200 nm can be achieved, giving better performance. The influence of angle of incidence on light absorption of the MIM system is also analyzed, and the angle tolerance for ≥90% broadband absorption of a TM wave is up to 40° in an environment with large refractive index. While the incident-angle dependence of the absorption of a TE wave is nearly the same for different circumstances, the situation is different for a TM wave.