• Korean Journal of Optics and Photonics
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• v.22 no.2
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• pp.102-107
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• 2011

In this paper, a small double ring resonator reflector was designed and fabricated using a polymer waveguide, and the measurement result was discussed. A widely tunable characteristic of the small double ring resonator caused by the Vernier effect, which results from the difference of the ring radii, was observed. The insertion loss of the double ring reflector was reduced by minimizing the device length to be as short as possible, and thus the output power and the SMSR (side mode suppression ratio) was greatly enhanced. The hybrid integrated laser based on the small double ring resonator reflector lased with the SMSR of 45 dB. In addition, the wide tuning range of 40 nm could be obtained by injecting a current of 30 mA to an electrode on top of the reflector.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.2
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• pp.165-170
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• 2016

Nano-scale power splitter based on curved plasmonic waveguides are designed by utilizing the multimode interference (MMI) coupler. To analyze easily the adaptive properties of plasmonic curverd multimode interference coupler(PC-MMIC), the curved form transforms equivalently into a planar form by using conformal transformation method. Also, effective dielectric method and longitudinal modal transmission-line theory are used for simulating the light propagation and optimizing the structural parameters at 3-D guiding geometry. The designed $2{\times}2$ PC-MMIC does not work well for quasi-TM mode case due to the bending structure, and it does not exist 3dB coupling property, in which the power splitting ratio is 50%:50%, for quasi-TE mode case. Further, the coupling efficiency is better when the signal is incident at channel with large curvature radius than small curvature radius.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.6
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• pp.1369-1375
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• 2007

The recent, a large capacity of telecommunication networks is required in order to it is in proportion to capacity of information communication increase and to satisfy a demand because of the demand about Internet, a multimedia service of internet, Video of internet protocol(VoIP), Audio/Video streaming. As a result, DWDM(Dense Wavelength Division Multiplexing)technologies are emerging to be a prevailing the method of solving it without additional optical fiber network building and high-speed equipment. Therefore this thesis proposed the optical filter of fiber/multilayer slab coupled structure combining it to multilayer slab waveguide by polishing the cladding of one side of fiber to design the optical filter having these functions. When a separation distance of fiber and slab was $3{\mu}m$, The optical filter proposed as the simulation result was satisfied with a DWDM filter characteristic with FWHM of 0.1nm on TM mode and TE mode as 32nm polarization independence in a communication window of $1.3{\mu}m$ when center wavelength was each ${\lambda}_0=1.274755{\mu}m$ and ${\lambda}_0=1.30591{\mu}m$.

• Applied Science and Convergence Technology
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• v.26 no.4
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• pp.79-85
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• 2017

The crack-free AlGaN template has been successfully grown by using selective area growth with triangular GaN facet. The triangular GaN stripe structure was obtained by vertical growth rate enhanced mode with low growth temperature of $950^{\circ}C$ and high growth pressure of 500 torr. The lateral growth rate enhanced mode of AlGaN for crack-free and flat surface was also investigated. Low pressure of 30 torr and high V/III ratio of 4400 were favorable for lateral growth of AlGaN. It was confirmed that the $4{\mu}m$ -thick $Al_{0.2}Ga_{0.8}N$ was crack-free over entire 2-inch wafer. The dislocation density of $Al_{0.2}Ga_{0.8}N$ was as low as ${\sim}7.6{\times}10^8/cm^2$ measured by cathodoluminescence. Based on the high quality AlGaN with low dislocation density, the ultraviolet laser diode epitaxy with cladding, waveguide and GaN/AlGaN multiple quantum well (MQW) was grown by metalorganic chemical vapor deposition. The stimulated emission at 349 nm with full width at half maximum of 1.8 nm from the MQW was observed through optical pumping experiment with 193 nm KrF laser. We also have fabricated the deep ridge type ultraviolet laser diode (UV-LD) with $5{\mu}m-wide$ and $700{\mu}m-long$ cavity for electrical properties. The turn on voltage was below 5 V and the resistance was ${\sim}55{\Omega}$ at applied voltage of 10 V. The amplified spontaneous emission spectrum of UV-LD was also observed from pulsed current injection.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.7
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• pp.1359-1366
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• 2007

The recent, a large capacity of communication is required in order to it is in proportion to capacity of information communication increase and to satisfy a demand because of the demand about Internet, a multimedia service of Video of internet protocol(VoIP), Audio/Video steaming. DWDM(Dense Wavelength Division Multiplexing) technique has been emerged as the method of solving it without additional optical fiber network building and hish-speed equipment. Therefore this thesis proposed the optical filter of fiber/multilayer slab coupled structure combining it to multilayer slab waveguide by polishing the cladding of one side of fiber to design the optical filter having these functions. The optical filter proposed as the simulation result satisfies DWDM filter characteristic; 1) when the separation distance between fiber and slab is $4.15{\mu}m$ at the communication window of $1.5{\mu}m$, the polarization independence is 65nm, 2) when the center wavelengths about TM mode and TE mode are each ${\lambda}_0=1.54946\;{\mu}m$ and ${\lambda}_0=1.6144\;{\mu}m$ and, FWHM(Full at Half Maximun) is 0.1nm.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.4
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• pp.217-222
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• 2015

Longitudinal transmission-line modal theory is applied to analyze the guiding mode characteristics along 1D & 2D grating patterns of plasmonic grating-assisted directional couplers (P-GADC) based on silicon waveguide. By defining supermodes amenable to rigorous analytical solutions and interference between even and odd modes, the field distributions of TE modes for each grating patterns are evaluated. The numerical result reveals that the field distribution with maximum coupling efficiency occurs at P-GADC composed by square grating pattern. That is, it reveals at a minium gap condition of grating period $d_{min}=8.8{\mu}m$ different from conventional phase-matching condition of GADC.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.62-67
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• 2002

It has been shown that the vibrational response of a tire can be represented by a set of decaying waves, each associated with a particular cross-sectional mode shape in the region near the contact patch. Thus, it can be concluded that tires can be effectively modeled as lossy waveguides. It has also been shown that the sound radiation from tires is mainly from the region close to the contact patch. In consequence, it may be computationally efficient to analyze tire vibration and sound radiation in the region close to the contact patch by using a hybrid finite element model in which the cross-section of a tire is approximated by 2-D finite elements while an analytical wave solution is assumed in the circumferential direction of the tire. In this article. a hybrid finite element was formulated based on a composite shell model. The dispersion relations for sample structures obtained by using the hybrid FE model were then compared with those obtained by using a full, three-dimensional FE model. It has been shown that the FE analysis made using the hybrid 2-D finite elements yields results in close agreement with the three-dimensional model.

• Proceedings of the KSRS Conference
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• v.1
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• pp.364-367
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• 2006

Nonlinear internal waves (NLIWs) are usually generated by nonlinear process on linear internal waves (IW). Near HengChun Ridge that links Taiwan and Luzon Islands, we found that there are linear internal waves following NLIW and they travel westward at different speed, about 1.5 m/s for IW and 2.9 m/s for NLIW. This phenomenon was observed on site with ship radar and echo sounders, and later verified with thermistor chain. West of Luzon Strait, the separation of NLIW are 5 km or more, while linear internal waves are lines of wave crests at nearly equal distance that is only a few hundred meters apart. The current hypothesis is that most of the energy of internal tide forms a beam that propagates upward from the eastern shoulder of ocean ridge and later interacts with sea surface and thermocline. The interaction with thermocline generates linear internal wave that propagate along the pycnocline at about 1.5 m/s. The interaction with sea surface scatters internal wave energy downward, ensonifies the water column and generates large nonlinear waves that propagate westward at 2.9 m/s as mode 1 in a waveguide.

• Korean Journal of Optics and Photonics
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• v.7 no.4
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• pp.414-418
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• 1996

An electro-optic polymer digital optical switch was fabricated by using a photobleached waveguide and a self-aligned electrode. It features wavelength insensitive operation, fabrication tolerance and flexible design. And its possible advantages include low coupling losses to the fibers and wide bandwidths. For improving its switching performance, the guided mode profiles of the photobleached waveguides were controlled by photobleaching times to achieve optimized coupling in the branch. And the self-aligned electrode was employed to achieve both efficient overlap of the optical and electric fields and easy introduction of the adiabatically tapered electrodes. The measured crosstalks were better than -21dB at 1.32 ${\mu}{\textrm}{m}$ and 1.55 ${\mu}{\textrm}{m}$, and the extinction ratios of each output port were also more than 20 dB.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.7 no.3
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• pp.254-262
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• 1996

In this paper, we present a polarizer that consists of three step rotary detents which can selectively convert linear polarzation into circular polarization and vice versa. For the design of the polarizer, the transmission line theory is applied to design the wa- veguide mode transducer for the modes to be smothly converted in waveguides, and a dielectric plate is inserted in circular waveguide for the conversion of a polarized wave with the angle of an inserted dielectric plate. Also, we simulated to obtain the optimum values of the transmission and the reflection coefficient characteristics at input and output port, and proved the propriety of the theory from the knowledge of measuring the constructed polarizer with the designed data.