• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.12
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• pp.1271-1276
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• 2004

Two-dimensionally arrayed nanocolumn lattices were fabricated by using double-exposure laser holographic method. The hexagonal lattice was formed by rotating the sample with 60 degree while the square lattice by 90 degree before the second laser-exposure. The reactive ion etching for a typical time of 30 min using CH$_4$/H$_2$ plasma enhanced the aspect-ratio by more than 1.5 with a slight increase of the bottom width of columns. The etch-damage was observed by photoluminescence (PL) spectroscopy which was removed by the wet chemical etching using HBr/$H_2O$$_2$/$H_2O$ solution, leading into the enhanced PL intensities of the PCs.

• Journal of the Microelectronics and Packaging Society
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• v.11 no.1
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• pp.13-19
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• 2004

This paper demonstrates the detailed study of a microstrip Yagi-Uda antenna with and without PBG structure at wireless LAN(5725∼5825 MHz) frequency band. The impedance bandwidth of the antenna with the PBG holes is greater than (about 30 MHz) that of its counter part without PBG holes. The measured gains of the antenna at the frequency band are 7 dB and 6 dB respectively for antenna with and without PBG. The improvement of gain of about 1 dB is likely due to the suppression of surface wave.

• Journal of IKEEE
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• v.11 no.4
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• pp.265-271
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• 2007

A new type of photonic bandgap(PBG) structures that consist of arrays of spiral metal patches is proposed in this paper. Reflection phases and radiation of these PBG structures are simulated by high frequency structure simulator(HFSS) to characterize their performance. The simulation results show that the resonant frequency of the proposed PBG structures gets significantly lower than those of the PBG structures with square metal patches, but that the radiation is nearly the same for both of the PBG structures. Analysis on reflection phases reveals that the lowering of the resonant frequency is associated with the increase in capacitance.

• Journal of the Optical Society of Korea
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• v.13 no.1
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• pp.33-36
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• 2009

Laser ablation with femtosecond lasers is highly promising for microfabrication of materials. Also, the high peak power of femtosecond lasers could induce a multiphoton absorption to ablate transparent materials. Similar results have also been were obtained in the case of optical fibers. In this paper, we present our experimental results of femtosecond laser microstructuring of optical fiber and its applications to microelectronic components and fiber optic devices. Finally, we directly produced micro holes with femtosecond laser pulses in a single step by moving an optical fiber in a preprogrammed structure. When water was introduced into a hole drilled from the bottom surface of the optical fiber, the effects of blocking and redeposition of ablated material were greatly reduced and the aspect ratio of the depth of the hole was increased. We have presented circular and rectangular-shaped holes in optical fiber.

• Journal of electromagnetic engineering and science
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• v.6 no.1
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• pp.62-70
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• 2006

This paper presents a new power plane design method incorporating a single geometry derived from a unit cell of photonic bandgap(PBG) structure. This method yields constantly wide suppression of parallel plate resonances from 0.9 GHz to 4.2 GHz and is very efficient to eliminate PCB resonances in a specified frequency region to provide effective suppression of simultaneous switching noise(SSN). It is shown that with only two cells the propagation of unwanted high frequency signals is effectively suppressed, while it could provide continuous return signal path. The measured results agree very well with theoretically predicted ones, and confirm that proposed method is effective for reducing EMI, with measured near-field distribution. The proposed topology is suitable for design of high speed digital system.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.106-107
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• 2007

We fabricated anodic aluminium oxides (AAO) on Si and sapphire substrates from the electrochemical reactions of thin AI films in an aqueous solution of oxalic acid. The thin AI films have deposited on Si and Sapphire substructure by using E-beam evaporation and thermal evaporation, respectively. The formation of AAO structures has investigated from FE-SEM measurement image and showed randomly distributed phase of nanoholes instead of the periodic lattice of photonic crystals. The AAO structure on sapphire shows the double layers of nanoholes.

• Journal of Integrative Natural Science
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• v.5 no.1
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• pp.27-31
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• 2012

Relationship between reflection resonance and applied current density in Bragg photonic crystal has been investigated. Multiple bit encodes of distributed Bragg reflector features have been prepared by electrochemical etching of crystalline silicon by using various square wave current densities. Optical characterization of multi-encoding of distributed Bragg reflectors on porous silicon was achieved by Ocean optics 2000 spectrometer for the search of possible applications of multiple bit encoding of distributed Bragg reflectors such as multiplexed assays and chemical sensors. The morphology and cross-sectional structure of multi-encoded distributed Bragg reflectors was investigated by field emission scanning electron micrograph.

• Journal of Integrative Natural Science
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• v.4 no.1
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• pp.7-10
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• 2011

Various types of smart dust based on photonic crystal exhibiting unique reflectivity were successfully obtained by an electrochemical etching of silicon wafer using square wave currents. Smart dust containing Bragg structure obtained from the sonication of DBR porous silicon film in solution retained its optical reflectivity. Field emission scanning electron micrograph (FE-SEM) was used to measure the size of optically encoded smart dust and its size can be tuned from few hundred nanometers to few microns depending on the duration of sonication. Optical characteristics of smart dust were used to investigate a possible applications such as chemical sensors.

• Current Optics and Photonics
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• v.6 no.1
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• pp.10-14
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• 2022

Low-threshold optical bistability is essential for practical nonlinear optical applications. Many bistable optical devices based on high-quality-factor resonators have been proposed to reduce the threshold intensity. However, demonstrating high-quality-factor resonance requires complex fabrication techniques. In this work, we numerically demonstrate optical bistability with bound states in the continuum in a simple one-dimensional Si photonic crystal. The designed structure supports bound states in the continuum, producing an ultrahigh quality factor without tough fabrication conditions. The threshold intensity of the designed device is 150 MW/cm² at the optical communication wavelength. This scheme may lead to a new class of nonlinear photonics.

• Journal of electromagnetic engineering and science
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• v.5 no.4
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• pp.204-207
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• 2005

In this paper, PBG structure and feedforward circuit has been used to suppress the phase noise of the oscillator. Microstrip line resonator have low Q, but we can obtain high LO power by feedforward circuit and improve the resonator Q by the PBG, simultaneously. The proposed oscillator which uses PBG and feedforward circuit shows 0${\~}$20 dB phase noise reduction compared to the conventional oscillator. We have obtained -115.8 dBc of phase noise at 100 kHz offset from 2.4 GHz center.