• Korean Chemical Engineering Research
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• v.53 no.6
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• pp.776-782
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• 2015

$TiO_2-SnO_2$ nanoparticles with an average diameter of 3~5 nm were synthesized by hydrolysis of titanium tetraisopropoxide (TTIP) and tin chloride to depress the photocatalytic activity of $TiO_2$ nanoparticles. Organic-inorganic hybrid coating solutions were prepared by reacting the $TiO_2-SnO_2$ nanoparticles with 3-glycidoxypropyl trimethoxysilane (GPTMS) by the sol-gel method. The hard coating films with high refractive index were obtained by curing thermally at $120^{\circ}C$ after spin-coating the coating solutions on the polycarbonate (PC) sheets. The coating films from $TiO_2-SnO_2$ nanoparticles showed an improved pencil hardness of 3H compared to 2H of the coating films from $TiO_2$ nanoparticles. Besides, the refractive index of the coating films from $TiO_2-SnO_2$ nanoparticles enhanced from 1.543 to 1.623 at 633 nm as the Sn/Ti molar ratio increased from 0 to 0.5.

• Journal of Korean Ophthalmic Optics Society
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• v.4 no.1
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• pp.45-49
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• 1999

To prepare high-transmittance films, thin films were fabricated on the microscope slide glasses with silicon alkoxides and boric acids as starting materials by using a dip-coating technique. Thicknesses of the thin films were controled as viscosity of the sol used and composition of the $B_2O_3$ was changed at 5, 10, 15 and 20 mol%. Transmittance at visible range and IR transmittance of the films according to the composition were measured, and refractive index of the films were analyzed also. Maximum transmittance at visible range and minimum refractive index were obtained at 15 mol% $B_2O_3$. We will discuss a decrease of the transmittance at 20 mol% on the basis of the refractive index.

• Korean Chemical Engineering Research
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• v.52 no.3
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• pp.388-394
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• 2014

Inorganic-organic hybrid coating solutions were synthesized using titania sol from titanium isopropoxide (TTIP) as an inorganic component and mixture of two or three types of silane coupling agents, such as methacryloxypropyl trimethoxysilane (MPTMS), aminopropyl triethoxysilane (APS), glycidoxypropyl trimethoxysilane (GPTMS) and vinyltriethoxysilane (VTES) as an organic component. The hard coating films were obtained by spin-coating on the polycarbonate sheets and curing the inorganic-organic hybrid coating solutions. The coating films made from the mixture of two types of silane coupling agents showed poor pencil hardness and adhesion, while those from the mixture of three types of silane coupling agents exhibited an improved pencil hardness of 2H~4H and adhesion of 5B. The refractive indexes of coating films were increased from 1.56 to 1.63 at 550 nm by increasing the content of titania sols from 20 to 30 g.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.5
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• pp.31-40
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• 2002

We propose a novel ultra-short asymmetric vertical directional coupler switch (VDCS) with high extinction ratios larger than 30㏈ composed of switching operation induced section (SOIS), extinction ratio adjusted section (ERAS), and extinction ratio enhanced section (ERES). In this VDCSs, switching operation is achieved by changing the refractive index of one core in SOIS. The improvement of extinction ratios larger than 30㏈ for both cross and bar states is achieved by controlling the asymmetry of refractive indices between both cores in ERES. After propagating through ERAS with symmetry in the structure, different extinction ratios between cross and bar states at the end of SOIS are changed to the same value. For this reason, the optimum asymmetry of the refractive indices of cores to have the maximum extinction ratios and the lengths of ERES are the same for cross and bar states. Design guidelines to achieve high extinction ratios with large tolerances are presented.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.5
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• pp.69-79
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• 1999

In this paper, we proposed a diffuion model of Ti diffused lithium niobate optical waveguide for fabricating waveguides with high refractive index and compared with conventional one. The achivement of low optical insertion loss between waveguide interface and single mode fibers was discussed as a function of Ti thickness for $\lambda$=1.55$\mu\textrm{m}$ The proposed diffusion method exhibited higher refractive index waveguide than conventional one for $\lambda$=0.6328$\mu\textrm{m}$ We have achieved the total fiber-waveguide-fiber insertion loss as low as 0.5dB/cm in z-cut and 1$\pm$0.5dB/cm in x-cut for both TM and TE mode of Mach-Zehnder interferometric waveguide in the range of Ti thickness 1000-1400$\AA$ for $\lambda$=1.55$\mu\textrm{m}$ From these results, this diffusion model for making a low loss waveguide can be used for low-power-modulators and switches.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.12
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• pp.1367-1374
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• 2008

A new high-gain Fabry-$P{\acute{e}}rot$ cavity antenna for wireless broadband internet(Wibro) base station antennas, which is covered with metamaterial superstrate presenting simultaneous negative values of permittivity and permeability, is proposed. To facilitate the fabrication process using the printed circuit board(PCB) technology of today, a new planar-type metamaterial superstrate is designed, which shows negative and low positive values of a refractive index near the Wibro service frequency band. And the principle of antenna gain enhancement is analyzed from the two different view points of effectively low refractive index and of the Fabry-$P{\acute{e}}rot$ resonance condition. Single square patch antenna is used as a feeder. The separation distance is determined by considering the reflection phases of the metamaterial superstrate and the substrate satisfying Fabry-$P{\acute{e}}rot$ resonance condition, respectively. Comparison between the prediction and the measurement shows good agreement, which verifies the validity of our design approach.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.23 no.6
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• pp.157-162
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• 2023

A highly sensitive refractive index bio-sensor based on grating-assisted strip directional coupler (GASDC) is proposed. The sensor is designed using two asymmetric strip waveguides with a top-loaded grating structure in one of the waveguides. Maximum light couples from one waveguide to the other at the resonance wavelength satisfying phase-matching condition (PMC), and it shows that the change in phase-matching condition with the change in refractive index of the analyte medium in the cover region can be used as a measure of the sensitivity. The proposed sensor will be an on-chip device with a high refractive index sensitivity, and the sensor configuration offers a low propagation loss, thereby enhancing the sensitivity. Furthermore, variation of the sensitivity with the waveguide parameters of sensor is evaluated to optimize the design.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.430-433
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• 2004

The ophthalmic lens manufacturing processes need to extract the aspherical surface equation from the unknown surface since its real profile can be adjusted by the process variables to make the ideal curve without the optical aberration. This paper presents a procedure to get the aspherical surface equation of an aspherical ophthalmic lens. Aspherical form generally consists of the Schulz formula to describe its profile. Therefore, the base curvature, conic constant, and high-order polynomial coefficient should be set to the original design equation. To find an estimated aspherical profile, firstly lens profile is measured by a contact profiler, which has a sub-micrometer measurement resolution. A mathematical tool is based on the minimization of the error function to get the estimated aspherical surface equation from the scanned aspherical profile. Error minimization step uses the Nelder-Mead simplex (direct search) method. The result of the refractive power measurement is compared with the curvature distribution on the estimated aspherical surface equation

• The Korean Journal of Food And Nutrition
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• v.13 no.5
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• pp.425-433
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• 2000

This study was conducted to estimate the prevalence of ametropias such as myopia and hyperopia from the community based population study. Another purpose of this study was to determine the association between ametropia and nutrient intake. The study subjects was 492 residents over 20 years of age residing in Kuri City. Ametropia was tested based on re(rector error using auto referactor. Nutrient intake was estimated from the dietary survey using 24 hour recall method. As a result of data analysis, the prevalence of myopia was 57% and that of hyperopia was 11%. Such a high rate of ametropia prevalence may suggest the increasing risk of eye health in a Korean society. Nutrient intake of myopia group was 5∼15% higher than that of normal group in most of the nutrients. Whereas intake of most nutrient except calcium, retinal, fiber for the hyperopia group was lower than that of normal group. The result may suggest that inbalance of nutrient intake has been related with ametropia.

• Journal of information and communication convergence engineering
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• v.14 no.3
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• pp.163-170
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• 2016

Because of rapid technological advancements, increased data rate support has become the key criterion for future communication medium selection. Multimode optical fibers and multicore optical fibers are well matched to high data rate throughput requirements because of their tendency to support multiple modes through one core at a time, which results in higher data rates. Using the numerical mode solver OptiFiber, we have designed a concentric core fiber by investigating certain design parameters, namely core diameter (µm), wavelength (nm), and refractive index profile, and as a result, the number of channels, material losses, bending losses, polarization mode dispersion, and the effective nonlinear refractive index have been determined. Space division multiplexing is a promising future technology that uses few-mode fibers in parallel to form a multicore fiber. The experimental tests are conducted using the standard second window wavelength of 1,550 nm and simulated results are presented.