• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.12B
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• pp.1754-1757
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• 2001

In this paper, a R-band hybrid amplifier with the coplanar waveguide(CPW) and the photonic bandgap(PBG) structure is designed and fabricated. The PBG and the CPW techniques are simultaneously employed in amplifier to improve the power added efficiency(PAE) and the IMD(Intermodulation Distortion) in R-band. In this paper, the PBG structures are optimized to obtain matching network. The output impedance of amplifier and the input impedance of PBG are matched to minimize the return loss. The PAE and the IMD were improved 15% and 4.5dB compared with the conventional amplifier, respectively.

• Journal of the Optical Society of Korea
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• v.16 no.3
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• pp.282-287
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• 2012

In this paper, we have proposed a principle to design a compact and temperature independent electro-optic switch based on a slotted photonic crystal directional coupler (SPCDC). Infiltration of the slotted silicon photonic crystal with polymer enhances the slow light and decreases the switching length, whereas the different signs of thermo-optic coefficients of the polymer and silicon make the proposed switch stable within $25^{\circ}C$ to $85^{\circ}C$ temperature range. The SPCDC structure is modified to increase poling efficiency of the polymer in the slot and to flatten the dispersion diagram of the even mode to minimize the switching length.

• Current Optics and Photonics
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• v.3 no.5
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• pp.438-444
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• 2019

In this theoretical study, a line-defect photonic-crystal waveguide hosted in an annular photonic crystal was demonstrated to provide high-performance slow light with a wide band, low group-velocity dispersion, and a large normalized delay-bandwidth product. Combined with structural-parameter optimization and selective optofluid injection, the normalized delay-bandwidth product could be enhanced to a large value of 0.502 with a wide bandwidth of 58.4 nm in the optical-communication window, for a silicon-on-insulator structure. In addition, the group-velocity dispersion is on the order of $10^5$ ($ps^2/km$) in the slow-light region, which could be neglected while keeping the signal transmission unchanged.

• Transactions on Electrical and Electronic Materials
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• v.9 no.4
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• pp.163-168
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• 2008

Photonic crystal structures have been received considerable attention due to their high optical sensitivity. One of the techniques to construct their structure is the dip-pen lithography (DPN) process, which requires a nano-scale resolution and high reliability. In this paper, we propose a two dimensional photonic crystal array to improve the sensitivity of optical biosensor and DPN process to realize it. As a result of DPN patterning test, we have observed that the diffusion coefficient of the mercaptohexadecanoic acid (MHA) molecule ink in octanol is much larger than that in acetonitrile. In addition, we have designed and fabricated optical waveguides based on the mach-zehnder interferometer (MZI) for application to biosensors. The waveguides were optimized at a wavelength of 1550 nm and fabricated according to the design rule of 0.45 delta%, which is the difference of refractive index between the core and clad. The MZI optical waveguides were measured of the optical characteristics for the application of biosensor.

• Macromolecular Research
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• v.14 no.2
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• pp.155-165
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• 2006

The present article describes the experimental and theoretical observations on the formation of holographic, polymer-dispersed, liquid crystals and electrically switchable, photonic crystals. A phase diagram of the starting mixture of nematic liquid crystal and photo-reactive triacrylate monomer was established by means of differential scanning calorimetry (DSC) and cloud point measurement. Photolithographic patterns were imprinted on the starting mixture of LC/triacrylate via multi-beam interference. A similar study was extended to a dendrimer/photocurative mixture as well as to a single component system (tetra-acrylate). Theoretical modeling and numerical simulation were carried out based on the combination of Flory-Huggins free energy of mixing and Maier-Saupe free energy of nematic ordering. The combined free energy densities were incorporated into the time-dependent Ginzburg-Landau (Model C) equations coupled with the photopolymerization rate equation to elucidate the spatio-temporal structure growth. The 2-D photonic structures thus simulated were consistent with the experimental observations. Furthermore, 3-D simulation was performed to guide the fabrication of assorted photonic crystals under various beam-geometries. Electro-optical performance such as diffraction efficiency was evaluated during the pattern photopolymerization process and also as a function of driving voltage.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.276-276
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• 2010

Large-area micropatterned array of Co/Ni bilayer anti-dots was fabricated using photolithography and wet etching process. The surface morphology as well as the surface topography was checked by scanning electron microscopy and atomic force microscopy, whereas the magnetic properties were studied by magneto-optical Kerr effect (MOKE) and magnetic force microscopy (MFM). Systematic studies of the magnetic-reversal mechanism, the in-plane anisotropy and the switching field properties were carried out. To get a comprehensive knowledge about the domain configuration, we also employed OOMMF simulations. It was found from the MOKE measurements that a combined effect of configurational and the magneto-crystalline anisotropy simultaneously works in such micropatterned bilayer structures. In addition, the inclusion of holes in the uniform magnetic film drastically affected the switching field. The MFM images show well-defined domain structures which are periodic in nature. The micromagnetic simulations indicate that the magnetization reversal of such a structure proceeds by formation and annihilation of domain walls, which were equally manifested by the field-dependent MFM images. The observed changes in the magnetic properties are strongly related to both the patterning that hinders the domain-wall motion and to the magneto-anisotropic bilayered structure.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.4
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• pp.244-248
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• 2015

We proposed and demonstrated the double layered metallic nano-hole structure using polystyrene beads process to enhance the sensitivity of surface plasmon resonance (SPR). The double layered SPR structures are calculated using the finite-difference time-domain (FDTD) method for the width, thickness, and period of the metallic nano-hole structures. The thickness of the metal film and the metallic nano-hole is 30 and 20 nm in the 214 nm wide nano-hole size, respectively. The double layered SPR structures are fabricated with monolayer polystyrene beads of 420 nm wide. The sensitivities of the conventional SPR sensor and the double layered SPR sensor are obtained to 42.2 and 52.1 degree/RIU, respectively.

• Journal of Magnetics
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• v.11 no.4
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• pp.195-207
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• 2006

The recently published and new results on design and fabrication of magnetophotonic crystals of different dimensionality are surveyed. Coupling of polarized light to 3D photonic crystals based on synthetic opals was studied in the case of low dielectric contrast. Transmissivity of opals was demonstrated to strongly depend on the propagation direction of light and its polarization. It was shown that in a vicinity of the frequency of a single Bragg resonance in a 3D photonic crystal the incident linearly polarized light excites inside the crystal the TE- and TM-eigen modes which passing through the crystal is influenced by Brags diffraction of electromagnetic field from different (hkl) sets of crystallographic planes. We also measured the faraday effect of opals immersed in a magneto-optically active liquid. It was shown that the behavior of the faraday rotation spectrum of the system of the opal sample and magneto-optically active liquid directly interrelates with transmittance anisotropy of the opal sample. The photonic band structure, transmittance and Faraday rotation of the light in three-dimensional magnetophotonic crystals of simple cubic and face centered cubic lattices formed from magneto-optically active spheres where studied by the layer Korringa-Kohn-Rostoker method. We found that a photonic band structure is most significantly altered by the magneto-optical activity of spheres for the high-symmetry directions where the degeneracies between TE and TM polarized modes for the corresponding non-magnetic photonic crystals exist. The significant enhancement of the Faraday rotation appears for these directions in the proximity of the band edges, because of the slowing down of the light. New approaches for one-dimensional magnetophotonic crystals fabrication optimized for the magneto-optical Faraday effect enhancement are proposed and realized. One-dimensional magnetophotonic crystals utilizing the second and the third photonic band gaps optimized for the Faraday effect enhancement have been successfully fabricated. Additionally, magnetophotonic crystals consist of a stack of ferrimagnetic Bi-substituted yttrium-iron garnet layers alternated with dielectric silicon oxide layers of the same optical thickness. High refractive index difference provides the strong spatial localization of the electromagnetic field with the wavelength corresponding to the long-wavelength edge of the photonic band gap.

• Journal of Integrative Natural Science
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• v.3 no.3
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• pp.138-142
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• 2010

Polystyrene thin films containing Bragg structures have been successfully obtained by the removal of DBR porous silicon films from the DBR structured porous silicon/polystyrene composite film in HF/$H_2O$ mixture solution and by replicating the nano-structures of porous silicon containing Bragg structure. Polystyrene thin films containing Bragg structures displayed unique optical reflection resonances in optical reflection spectrum. This optical reflection band was resulted from the interference of reflection wavelength at Bragg structure of polystyrene thin films. The wavelength of reflection resonances could be modified by the change of Bragg structure of the master. Polystyrene thin films containing Bragg structures were flexible and maintained their optical characteristics upon bending. The Polystyrene thin films replicate the photonic features and the nanostructure of the master.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2002.11a
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• pp.413-422
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• 2002

A novel photonic bandgap(PBG) structure is proposed and measured for wide bandgap and compact circuit applications. The proposed structure realizes the ultra-wideband bandgap(2-octave) characteristics by superposing two different PBG structures into a coupled double-plane configuration. A low pass filter fabricated using 3-period of the PBG cells shows 2-octave 10 ㏈ stopband from 4.3 to 16.2 ㎓ and 0.2 ㏈ insertion loss in the passband. Moreover, we confirmed that 44∼70 % size reduction can be achieved using the proposed PBG structures. We expect this novel double-plane PBG structure is widely used for compact and wideband circuit applications, such as compact high-efficiency power amplifiers using harmonic tuning techniques.