• 한국레이저가공학회지
• /
• 제14권3호
• /
• pp.17-20
• /
• 2011

We fabricated a multi-layer diffraction grating inside fused silica glass by using a femtosecond laser direct writing method. The femtosecond laser with a wavelength of 515 nm, a pulse width of 250 fs, a repetition rate of 100 kHz, and an average output power of 6 W was used. Two layer diffraction grating with a grating period of $6{\mu}m$ was successfully fabricated with the layer gap of 0.5, 1, 2, 3, and $5{\mu}m$, respectively. Also, we investigated the diffraction pattern by illuminating a He-Ne laser beam. Finally, we demonstrated the diffraction grating with a grating period of $3{\mu}m$ by adjusting the gap of each layer with a grating period of $6{\mu}m$. Femtosecond laser direct writing technology of multi-layer has a potential to fabricate the diffraction grating with a grating period of below $1.5{\mu}m$.

• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 1998년도 Proceedings of International Symposium on Remote Sensing
• /
• pp.399-403
• /
• 1998

Absorption coefficient per mass unit of particles, specific absorption coefficient, is one of main parameters in developing algorithms for ocean color remote sensing. Specific absorption coefficient of chlorophyll (a$^*_{ph}$) and suspended sediment (SS) were analyzed by "wet filter technique" and "Kishino method" for data sets observed in the Yellow and Mediterranean Seas. A new data-recovering method for the filter technique was also developed using spectrum slopes. This method recovered the baseline of spectrum that was often missed in the Kishino method. High a$^*_{ph}$($\lambda$) values in the oligotrophic Mediterranean Sea and low values in the Yellow Sea were observed, spanning over the range of 0.02 to 0.12 $m^2$/mg, at the chlorophyll maximum absorption wavelength 440nm. The empirical relationship between a$^*_{ph}$ and chlorophyll concentration was found to fit a power function, which was slightly different from that proposed by Bricaud et ai. (1995). Absorption specific coefficients for suspended sediment (a$^*_{SS}$) didn't show any relationship with concentrations of suspended sediment. However, the average value of a$^*_{SS}$ at 440nm was close to the specific absorption coefficient of soil (loess) measured by Ahn (1990). The more-pronounced variability of a$^*_{SS}$ than a$^*_{ph}$ perhaps can explain more wide range of size-distribution for SS, which were determined by their specific gravity and agitation of water mass in the sea surface.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2011년도 추계학술대회 초록집
• /
• pp.62.1-62.1
• /
• 2011

The structural, optical, and electrical properties of Ga-doped ZnO (GZO) thin films on glass substrates grown by radio-frequency(RF) magnetron sputtering were investigated. The flow ratio of Ar was varied as a deposition parameter for growing high-quality GZO thin films. The structural properties and surface morphologies of GZO were characterized by the X-ray diffraction. To analyze the optical properties of GZO, the optical absorbance was measured in the wavelength range of 300-1100 nm by using UV-VIS spectrophotometer. The optical transmittance, absorption coefficient, and optical bandgap energy of GZO thin films were calculated from the measured data. The crystallinity of GZO thin films is improved and the bandgap energy increases from 3.08 to 3.23eV with the increasing Ar flow ratio from 10 to 100 sccm. The average transmittance of the films is over 88% in the visible range. The lowest resistivity of the GZO is $6.215{\times}10^{-4}{\Omega}{\cdot}cm$ and the hall mobility increases with the increasing Ar flow ratio. We can optimize the characteristics of GZO as a transparent electrode for thin film solar cells by controlling Ar flow ratio during deposition process.

• 한국염색가공학회지
• /
• 제19권6호
• /
• pp.28-34
• /
• 2007

The optical and physical properties of alkyl-substituted anthraquinoid dyes were investigated in terms of dyeing of pure polypropylene fiber. The length of alkyl substituents of the dyes did not affect the molar extinction coefficient and maximum absorption wavelength of them. The use of a double-tailed cationic surfactant, didodecyldimethylammonium bromide(DDDMAB), could make the hydrophobic dyes dispersed in water effectively. As the amount of DDDMAB increased, the average particle size of dye dispersion decreased. Maximum color strength of the fabrics was shown in the case that 1.5 molar ratio of DDDMAB was used. As for the fastness properties, commercially acceptable result was obtained in general.

• 반도체디스플레이기술학회지
• /
• 제6권3호
• /
• pp.35-39
• /
• 2007

ITO(Indium Tin Oxide) is the most attractive TCO(Transparent Conducting Oxide) materials for LCD, PDP, OLEDs and solar cell, because of their high optical transparency and electrical conductivity. However due to the shortage of indium resource, hard processing at low temperature, and decrease of optical property during hydrogen plasma treatment, their applications to the display industries are limited. Thus, recently the Al-doped ZnO(AZO) has been studied to substitute ITO. In this study, we have investigated the effect of different substrate temperature(RT, $150^{\circ}C$, $225^{\circ}C$, $300^{\circ}C$) and working pressure(10 mTorr, 20 mTorr, 30 mTorr, 80 mTorr) on the characteristics of AZO(2 wt.% Al, 98 wt.% ZnO) films deposited by RF-magnetron sputtering. We have obtained AZO thin films deposited at low temperature and all the deposited AZO thin films are grown as colunmar. The average transmittance in the visible wavelength region is over 80% for all the films and transmittance improved with increasing substrate temperature. Electrical properties of the AZO films improved with increasing substrate temperature.

• Journal of Astronomy and Space Sciences
• /
• 제29권2호
• /
• pp.199-208
• /
• 2012

The world's first geostationary ocean color imager (GOCI) is a three-mirror anastigmat optical system 140 mm in diameter. Designed for 500 m ground sampling distance, this paper deals with on-orbit modulation transfer function (MTF)measurement and analysis for GOCI. First, the knife-edge and point source methods were applied to the 8th band (865 nm) image measured April 5th, 2011. The target details used are the coastlines of the Korean peninsula and of Japan, and an island 400 meters in diameter. The resulting MTFs are 0.35 and 0.34 for the Korean East Coastline and Japanese West Coastline edge targets, respectively, and 0.38 for the island target. The daily and seasonal MTF variations at the Nyquist frequency were also checked, and the result is $0.32{\pm}0.04$ on average. From these results, we confirm that the GOCI on-orbit MTF performance satisfies the design requirements of 0.32 for 865 nm wavelength.

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
• /
• pp.1437-1439
• /
• 2009

Electrical and optical properties of $SiO_2$-doped ZnO (SZO) films on the corning 7059 glass substrates by using rfmagnetron sputtering method are investigated. The deposition rate becomes maximum near 3 wt.% and gradually decreases when the $SiO_2$ content further increases. The growth rates at 3 wt.% is $4^{\circ}$A/s. We found that the average transmittance of all films is over 80% in the wavelength range above 500 nm. The optical band gap decreases from 3.52 to 3.33 eV with an increase in thickness. X-ray diffraction patterns show that the film with a relatively low $SiO_2$ content (< 4 wt.%) is amorphous. SZO films at the $SiO_2$ contents of 2 wt.% shows the resistivity of about $3.8{\times}10^{-3}{\cdot}cm$. The sheet resistance decreases with increasing the heat treatment temperature.

• Transactions on Electrical and Electronic Materials
• /
• 제10권6호
• /
• pp.185-188
• /
• 2009

The effects of the growth temperature on the properties of ZnO thin films were investigated by using X-ray diffraction, scanning electron microscopy, ultraviolet-visible spectrophotometry, and Hall measurements. The ZnO films were deposited by rf magnetron sputtering at various growth temperatures in the range of 100-$400{^{\circ}C}$. A strong c-axis preferred orientation is observed for all of the samples. As the growth temperature increases, the crystalline orientation of the ZnO (002) plane is not changed, but the full width at half maximum gets smaller. The dependence of the electron concentration, mobility, and resistivity on the growth temperature exhibits that the ZnO films have a higher electron concentration at higher temperatures, thus giving them a low resistivity. The optical transmittance and band gap energy, calculated from the spectra of optical absorbance, show a significant dependence on the growth temperature. As for the sample grown at $100{^{\circ}C}$, the average transmittance is about 90% in the visible wavelength range and the band gap is estimated to be 3.13 eV.

• ETRI Journal
• /
• 제35권4호
• /
• pp.587-593
• /
• 2013

We demonstrate semitransparent organic photovoltaics (OPVs) based on thin metal electrodes and polymer photoactive layers consisting of poly(3-hexylthiophene) and [6,6]-phenyl $C_{61}$ butyric acid methyl ester. The power conversion efficiency of a semitransparent OPV device comprising a 15-nm silver (Ag) rear electrode is 1.98% under AM 1.5-G illumination through the indium-tin-oxide side of the front anode at 100 $mW/cm^2$ with 15.6% average transmittance of the entire cell in the visible wavelength range. As its thickness increases, a thin Ag electrode mainly influences the enhancement of the short circuit current density and fill factor. Its relatively low absorption intensity makes a Ag thin film a viable option for semitransparent electrodes compatible with organic layers.

• 천문학회보
• /
• 제37권2호
• /
• pp.106.1-106.1
• /
• 2012

The Gegenschein is a faint glow around the anti-solar point caused by the interplanetary dust particle(IDP)'s back-scattering enhancement. From the previous low resolution observations, the overall morphology of the Gegenschein has been intensively studied. However, sub-degree scale fine structure of the Gegenschein is still not well known, even though the detailed morphology of the Gegenschein within a few degree from the anti-solar point may supply pivotal information about the property of the IDPs. We made optical CCD observations of the Gegenschein between 2003 March and 2006 November. From the observations, we succeeded in making high resolution images of the Gegenschein, with unprecedented 1.'4 resolution. Our results concur with IDP cloud model based on the infrared observations combined with scattering phase function derived from low resolution data. The only exception is the anti-solar point. We found a steep additional brightness enhancement existing at the exact anti-solar point. Plausible explanation of the finding is that the IDPs are significantly larger than observing wavelength, and have irregular morphology or inhomogeneous internal structure. Furthermore, we measured average geometric albedo of the IDPs from the optical brightness of the anti-solar point. The geometric albedo was $0.06{\pm}0.01$, similar to those of comets or C-type asteroids.