• Transactions of the Society of Information Storage Systems
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• v.4 no.1
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• pp.13-18
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• 2008

Scratches are observed on a polymer cover-layer of near-field recording (NFR) media after a servo test with rotating disc. The scratches are formed by the collision of a solid immersion lens (SIL)-media. One of the possible ways to avoid the scratch problem is to coat a dielectric protective film on the polymer cover-layer which enhances the hardness of the surface. The surface with hard characteristics in the surface reduces the scratch problem in the cover-layer. Not only the mechanical properties but also the optical properties should be controlled. Specifically, the refractive index of the dielectric protective film should be matched with the polymer cover-layer not to lose light at the interface due to the difference of the refractive index. The refractive index of the dielectric film can be tailored by controlling process parameters during sputtering and matched with that of the polymer cover-layer.

• International Journal of Fluid Machinery and Systems
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• v.2 no.2
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• pp.121-126
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• 2009

The internal flow field in a centrifugal pump working at the several flow conditions has been measured by using the particle image velocimetry (PIV) technique with the laser induced fluorescence (LIF) particles and the refractive index matched (RIM) facilities. The impeller of the centrifugal pump has an outlet diameter in 100mm, and consists of six two-dimensional curvature backward swept blades of constant thickness. Measured results give reliable flow patterns in the pump. It is obvious that application of LIF particle and RIM are the key methods to obtain the right PIV measured results in pump internal flow.

• Transactions of the Society of Information Storage Systems
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• v.2 no.3
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• pp.189-195
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• 2006

Bragg detuning effect if, one of the serious problems if the photopolymer is used for the recording material of holography memories. And the critical reasons of that are known as the bulk refractive index change and shrinkage of recording material. However, the trials for analyzing the effect are mainly on the K-sphere and biased on the transmission hologram. So, we approached Bragg detuning effect numerically and applied the method to the transmission holograms and the reflection holograms all together. We simulated it with MATLAB. As a result, the bulk refractive index change causes+Bragg detuning effect on the transmission holograms and the reflection holograms. But the shrinkage leads to+Bragg detuning effect on the transmission hologram and-Bragg detuning effect on the reflective hologram. Compared to experimental result, the bulk refractive index change(${\fallingdotseq}4{\times}10^{-4}$) and the ratio of shrinkage to the thickness of the material(${\fallingdotseq}1.67{\times}10^{-3}$) could be matched with Bragg detuning effect on the transmission hologram and the reflection hologram.

• 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.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2007.04a
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• pp.128-129
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• 2007

$ZnS/Na_3AlF_6$ multi-layer thin film were produced by evaporation system. ZnS were selected as a high refractive index material and $Na_3AlF_6$ were selected as low refractive index material. Optical properties including color effect were systematically studied in terms of different optical thickness by spectrophotometer. In oder to compare with experimental data, the Essential Macleod Program(EMP) was adopted that simulation program. The thin film consisting of $ZnS/Na_3AlF_6$ multi-layer show the wave length of $530{\sim}600nm$, typically color range between purple, blue, green. It was confirmed that this experimental result was well matched with simulation data.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.11
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• pp.78-84
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• 1998

Refractive index was matched using the inhomogeneous dielectric layers to enhance the optical transmittance of surface discharge type AC PDP. The transmittance of upper panel which had two index-matched inhomogeneous dielectric layers was measured as 85%, and this result is regarded as 15% better transmittance than that of conventional structure, which is about 70%.

• Journal of Sensor Science and Technology
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• v.24 no.1
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• pp.1-5
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• 2015

The V-grooved single-mode fiber in which a surface part of the core was removed was investigated as a quasi-distributed water detection sensor. In the normal state, the V-grooved region is filled and covered with a specific RI (Refractive Index)-matched medium, and the sensor experiences minimal optical loss. As water invades the V-grooved region, the material is dissolved and removed, and a considerable optical loss occurs owing to the large RI difference between the fiber core and water. The experimental results showed the feasibility of the device as a sensor element of the quasi-distributed water detection sensor system based on general optical time domain reflectometry (OTDR).

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.1
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• pp.84-93
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• 1998

Planar graded index optical waveguides have been formed by Ag$^{+}$ ion exchange in the BK7 optical glass. The experimental results of diffusion and modal characteristics of Ag$^{+}$-Na$^{+}$ exchanged BK7 glass waveguides are presented. Measurements of the mode indices have been measured. We found the relations between the process and device parameters such as the diffusion depth and the square root of the diffusion time, diffusion coefficient and diffusion temperature, and diffusion ion concentration and surface index change. A theoretical gaussian function refractive index profile matched best with the measured data for all the guided modes. The empirical relations between the process and the device parameters are derived and subsequently used to formulate a systematic procedure for fabricating singlemode and multimode waveguides.uides.

• Polymer(Korea)
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• v.39 no.3
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• pp.370-381
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• 2015

In the system of poly(vinyl alcohol) (PVA)/dimethyl sulfoxide, the refractive index of polymer was very well matched to that of solvent and thus its scattered intensity could be minimized. After adding small amount of polystyrene latex particle (nominal diameter 200 nm), diffusion behavior of only probe particle was investigated against the concentration of polymer matrix by means of dynamic light scattering. The polymer concentration dependence of its reduced diffusion coefficient was able to be analysed with the stretched exponential function of the reduced concentration $C[{\eta}]$. In very dilute concentration regime, the depletion layer kept constant but at the early semi-dilute regime of $1{\leq}C[{\eta}]{\leq}2.5$, the concentration-dependent exponent of depletion layer ${\delta}$ was appeared to be -0.8 which was very close to theoretical one of -0.85. However it was also observed at the higher concentration that its layer thickness decreased more abruptly than theoretical expectation and this phenomenon was ascribed to Oosawa type attractive interaction between adjacent latex particles.

• Polymer(Korea)
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• v.31 no.4
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• pp.335-342
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• 2007

The goal of this study is to investigate the effect of molecular structure modifications on the kinetics of physical aging of thin films formed from 6FDA-based polyimides with time. The permeability for 6FDA-based polyimide thin films containing carboxyl acid groups commonly decreased 20-50% after the isothermal aging and the selectivity gained anywhere from 10% to 30% while the rate of permeability loss on the change of polymer structure showed different reciprocal relationship between 6FDA-6FpDA based polyimides and 6FDA-DAM based polyimides. The Lorenz-Lorentz equation was used to relate changes in refractive index to densification and volume relaxation with aging time. The permeability as a function of aging time fits the expected form $P=Ae^{(-B/f)}$. The results matched well with the data for different polymer membranes.