• Journal of Korean Ophthalmic Optics Society
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• v.18 no.1
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• pp.27-35
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• 2013

Purpose: The present study was conducted to investigate the changes in the physical properties of RGP lenses induced by the polishing during the process of RGP lens manufacturing, and further evaluate the differences in the actual wearer's comfort and the tear film break-up time caused by these changes. Methods: RGP lenses (fluorosilicone acrylate material) were divided into 4 groups by the different lens-polishing time like 0, 25, 50 and 100 seconds and the thickness, the surface roughness and the wetting angle of those lenses were compared. Furthermore, the comfortability of the lens wear was surveyed after applying these lenses on the subject's eyes with normal tear volume and the non-invasive tear break-up time of the wearers was measured. Results: The central thickness of 4 RGP lenses made of different lens-polishing time was not significantly different however, the lens surface was changed smoother after polishing to be confirmed by scanning electron microscopy. The wetting angle of the RGP lens significantly decreased in accordance with the increase of polishing time. Thus, the difference of approximately $16^{\circ}$ between 0 second and 100 seconds-polishing was statistically significant. The actual wearing feeling of RGP lens was tended to improve in accordance with the increase of the lens wettability however, it was not proportional improvement. The non-invasive tear break-up time of the lens wearers showed different aspect compared with the changes in lens wettability and the actual feeling of RGP lens wear. Conclusions: In this study, better lens wettability, thinner lens thickness, and/or improved lens surface induced by physical stimuli in the process of RGP lens manufacturing was not well-correlated with the increase of actual subjective/objective satisfaction in RGP lens wear. Thus, the consideration of physical properties of the lens as well as the lens wearers' physiological factors in the process of RGP lens manufacturing may be suggested.

• Korean Journal of Optics and Photonics
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• v.23 no.1
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• pp.12-16
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• 2012

In the paper, we fabricated a Ni master with $45^{\circ}$-mirror structures for flexible waveguide fabrication. The flexible waveguide films with embedded $45^{\circ}$-angled mirrors at the waveguide ends were successfully fabricated using a UV-imprint process. Next, in order to enhance the reflectivity of the mirrors, Ni(3 nm)-Au(200 nm) bilayers were evaporated on the $45^{\circ}$-angled facets through a locally opened thin mask using an electron beam evaporator. We measured propagation loss, bending loss, mirror loss and bending reliability of the fabricated waveguide.

• Korean Journal of Optics and Photonics
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• v.13 no.2
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• pp.105-112
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• 2002

We studied the optical and structural properties of conventional and ion-beam-assisted-deposition (IBAD) Nb$_2$O$_{5}$ films which were evaporated by an electron beam gun. The vacuum-to-air spectral shift and the cross sectional SEM images of the Nb$_2$O$_{5}$ films were investigated. The results show that the IBAD Nb$_2$O$_{5}$ films have a higher packing density than the conventional Nb$_2$O$_{5}$ films. The average refractive index of IBAD Nb$_2$O$_{5}$ films was increased, while the extinction coefficient was decreased compared with the conventional films. As the oxygen flow was increased, the average refractive index and extinction coefficient of the conventional and IBAD films decreased. Both the conventional and IBAD Nb$_2$O$_{5}$ films showed inhomogeneity in refractive index, and the degree of inhomogeneity of the IBAD Nb$_2$O$_{5}$ films became larger as the ion current density was increased. All Nb$_2$O$_{5}$ films were found to be amorphous by x-ray diffraction (XRD) analysis, and hence the crystal structure of Nb$_2$O$_{5}$ films was not changed by IBAD.

• Journal of the Korean Society of Food Science and Nutrition
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• v.38 no.9
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• pp.1284-1288
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• 2009

Identification of various inorganic compound crystals contained in solar salts, which are produced from 12 areas of Jeonnam, was firstly made by the X-ray diffraction (XRD) technique. The analysis of the XRD spectra was carried out on the basis of Joint Committee on Powder Diffraction Standards (JCPDS) data and the results of Energy Dispersive X-ray Spectrometer (EDX) measurements. In particular, the analysis of the XRD spectra supported that each solar salt contains $Na_2S$ (Shinan Jeungdo and Sinui), $KMgCl_3$ (Shinan Bigeum), $Ca(ClO_3)_2$ (Shinan Docho), $CaAl_4O_7$ (Haenam Songji), $CaSiO_3$ and $CaCl_2$ (Goheung) as inorganic compound crystals, which have not been reported for the solar salts. Also, the XRD results indicated that the solar salts maintain a cubic NaCl crystal structure without any change of lattice parameters etc. However, it was shown in the Field Emission Scanning Electron Microscope (FE-SEM) images that an external form of the solar salts has a lamination layer shape of a cubic structure, which is different from a simple cubic form for the purified salts and the reagent NaCl.

• Korean Journal of Optics and Photonics
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• v.21 no.1
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• pp.33-37
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• 2010

We performed time-domain terahertz (THz) spectroscopy to determine optical constants of highly conductive carbon nanotube (CNT) films. The CNT films have been fabricated on a flexible plastic substrate by using spin-coating or vacuum filtration. We found that the transmission of THz waves can be controlled by manipulating the thickness of the films and by post-treatments. From amplitude and phase information of the transmitted THz waves, we obtain optical constants such as refractive indices and dielectric constants of the CNT films. The frequency dependent dielectric constants show good metallic behaviors, relevant to the Drude free electron models with high plasma frequencies. It is also found that the dielectric constants are higher for the acid-treated films. Finally, the frequency dependent dielectric constants which are free from substrate effects have been demonstrated by using CNT films deposited on cellulose membranes.

• Analytical Science and Technology
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• v.11 no.6
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• pp.460-468
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• 1998

Schiff base ligands such as $SOPDH_2$, $SNDH_2$, $EBNH_2$, and $PBNH_2$ and their Co(II) complexes such as [$Co(II)(SND)(H_2O)_2$], [$Co(II)(SOPD)(H_2O)_2$], [$Co(II)(EBN)(H_2O)$], and [$Co(II)(PBN)(H_2O)$] have been synthesized. The mole ratio of Shiff base ligand to cobalt(II) for the Co(II) complexes was found to be 1:1. Also these complexes have been configurated with hexa-coordination. Reduction of dioxygen was investigated by cyclic voltammetry at glassy carbon electrodes modified with Schiff base Co(II) complexes in 1 M KOH aqueous solution. At modified glassy carbon electrode with Schiff base Co(II) complexes, reduction peak current of oxygen was increased and peak potential was shifted to more positive direction compared to bare glassy carbon electrode. The electrokinetic parameters such as number of electron and exchange rate constant were calculated from the results of cyclic voltammogrms. The reduction of dioxygen at glassy carbon electrode has been $2e^-$ reaction pathway. Exchange rate constant at glassy carbon electrode modified with Co(II) complexes was increased 2~10 times compared to bare electrode.

• Korean Journal of Optics and Photonics
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• v.18 no.5
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• pp.351-361
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• 2007

The samples composed of a GST thin film and the protective layers of $ZnS-SiO_2$ or $Al_2O_3$ coated on c-Si substrate were prepared by using the magnetron sputtering method. Samples of three different structures were prepared, that is, i) the GST single film on c-Si substrate, ii) the GST film sandwiched by the protective $ZnS-SiO_2$ layers on c-Si substrate, and iii) the GST film sandwiched by $Al_2O_3$ protective layers on c-Si substrate. The ellipsometric constants in the temperature range from room temperature to $700^{\circ}C$ were obtained by using the in-situ ellipsometer equipped with a conventional heating chamber. The measured ellipsometric constants show strong variations versus temperature. The variation of ellipsometric constants at the temperature region higher than $300^{\circ}C$ shows different behaviors as the ambient medium is changed from in air to in vacuum or the protective layers are changed from $ZnS-SiO_2$ to $Al_2O_3$. Since the long heating time of 1-2 hours is believed to be the origin of the high temperature variation of ellipsometric constants upon the heating environment and the protective layers, a PRAM (Phase-Change Random Access Memory) recorder is introduced to reduce the heating time drastically. By using the PRAM recorder, the GST samples are heated up to $700^{\circ}C$ decomposed preventing its partial evaporation or chemical reactions with adjacent protective layers. The surface image obtained by SEM and the surface micro-roughness verified by AFM also confirmed that samples prepared by the PRAM recorder have smoother surface than the samples prepared by using the conventional heater.

• Korean Journal of Optics and Photonics
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• v.14 no.1
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• pp.23-32
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• 2003

The spectroe-ellipsometric constant $\Delta$, Ψ and the ellipsometric growth curves at the wavelength of 632.8 nm are collected. These are critically examined to find out the optimum growth condition of phase change $Ge_2Sb_2Te_5(GST)$ thin films as an optical recording medium. GST films are prepared using DC magnetron sputtering technique, under the selected experimental conditions of Ar gas pressure (5 mTorr, 7 mTorr and 10 mTorr), DC power of sputtering gun (15 W, 30 W and 45 W), and substrate temperature (from room temperature to 18$0^{\circ}C$). Based on the three film model, the density distribution of deposited GST films are obtained versus Ar gas pressure and DC power by analyzing spectro-ellipsometric data. The calculated evolution curves at the wavelength of 632.8 nm, are fit into the in situ observed ones to get information about the evolution of density distribution during film growth. The density distribution showed different evolution curves depending on deposition conditions. The GST films fabricated at DC power of 30 W or 45 W, and at Ar gas pressure of 7 mTorr turned out to be the most homogeneous one out of those prepared at room temperature, even though the maximum density difference between the dense region and the dilute region of the GST film was still significant (~50%). Finally, in order to find the optimum growth condition of homogeneous GST thin films, the substrate temperature is varied while Ar gas pressure is fixed at 7 mTorr and DC power at 30 W and 45 W respectively. A monotonic decrease of void fraction except for a slight increase at 18$0^{\circ}C$ is observed as the substrate temperature increases. Decrease of void fraction indicates an increase of film density and hence an improvement of film homogeneity. The optimum condition of the most homogeneous GST film growth turned out to be 7 mTorr of Ar gas pressure, 15$0^{\circ}C$ of substrate temperature. and 45 W of DC power. The microscopic images obtained using scanning electron microscope, of the samples prepared at the optimum growth condition, confirmed this conclusion. It is believed that the fabrication of homogeneous GST films will be quite beneficial to provide a reliable optical recording medium compatible with repeated write/erase cycles.