• Journal of the Institute of Convergence Signal Processing
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• v.9 no.4
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• pp.261-271
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• 2008

Holographic volume grating couplers (VGCs) are become increasingly attractive device for the application of optical interconnects because of their higher preferential coupling, dry fabrication processing, compact, and low cost. In this paper, the analysis, design, and implementation of the waveguide-imbedded input-output VGC with $45^{\circ}$ grating slant angle using holographic photopolymer(Dupont HRF600-20) for guided-wave optical interconnection applications, are presented. To show the usefulness of the proposed VGC, we fabricated the VGCs operating at 632.8nm and 1550nm wavelengths and its results are presented. The measured input coupling efficiency of the single VGC with $0.5{\mu}m$ grating period at 632.8nm wavelength is above 86.6% for TE-polarization. The input coupling efficiency of the $1\times2$ VGC with $0.73068{\mu}m$ grating period at 1550nm wavelength is about 90.8%.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.11
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• pp.765-770
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• 2001

Metal-ferroelectric-insulator- semiconductor(MFTS) devices by using rapid thermal annealed (RTA) LiNbO$_3$/AIN/Si(100) structures were successfully fabricated and demonstrated nonvolatile memory operations. Metal-insulator-semiconductor(MIS) C-V properties with high dielectric AIN thin films showed no hysteresis and good interface properties. The dielectric constant of the AIN film calculated from the capacitance at the accumulation region in the capacitance-voltage(C-V) characteristics was about 8. The C-V characteristics of MFIS capacitor showed a hysteresis loop due to the ferroelectric nature of the LiNbO$_3$ thin films. Typical dielectric constant value of LiNbO$_3$ film of MFIS device was about 23. The memory window width was about 1.2 V at the gate voltage of $\pm$5 V ranges. Typical gate leakage current density of the MFIS structure was the order of 10$^{-9}$ A/$\textrm{cm}^2$ at the range of within $\pm$500 kV/cm. The ferroelectric capacitors showed no polarization degradation up to about 10$^{11}$ switching cycles when subjected to symmetric bipolar voltage pulse(peak-to-peak 8 V, 50 % duty cycle) in the 500 kHz.

• Journal of the Korean Ceramic Society
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• v.48 no.4
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• pp.307-311
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• 2011

Solid solutions of the (1-x)$BiFeO_3-xSrTiO_3$ ceramic system (x = 0~0.4) are explored here in attempts to obtain multiferroic properties in these systems. The polarization-electric field hysteresis, magnetization-magnetic field curves, and dielectric properties are also characterized. This solid-solution system shows a crystal structural transition from a noncentrosymmetric (R3c) structure to a centrosymmetric (Pm-3m) structure at 0.3 < x < 0.4. The solid solution ceramic shows unsaturated M-H behavior and low remanent magnetization over the composition region of 0.1 ${\leq}$ x ${\leq}$ 0.3. The $0.7BiFeO_3-0.3SrTiO_3$ system shows the largest value of $M_s$ at 0.17 emu/g and the smallest value of $H_c$ at 1.06 kOe. The P-E hysteresis curves were not saturated under an electric field as high as E = 70 kV/cm. This system is considered to have multiferroic characteristics in the composition range of 0.1 ${\leq}$ x ${\leq}$ 0.3.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.624-627
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• 2003

The BLT thin-films were one of the promising ferroelectric materials with a good leakage current and degradation behavior on Pt electrode. The BLT target was sintered at $1100^{\circ}C$ for 4 hours at the air ambient. $Bi_{3.25}La_{0.75}Ti_3O_{12}$ (BLT) thin-film deposited on $Pt/Ti/SIO_2/Si$ wafer by rf magnetron sputtering method. At annealed $700^{\circ}C$, (117) and (006) peaks appeared the high intensity. The hysteresis loop of the BLT thin films showed that the remanent polarization ($2Pr=Pr^+-Pr^-$) was $16uC/cm^2$ and leakage current density was $1.8{\times}10^{-9}A/cm^2$ at 50 kV/cm with coersive electric field when BLT thin-films were annealed at $700^{\circ}C$. Also, the thin film showed fatigue property at least up to $10^{10}$ switching bipolar pulse cycles under 7 V. Therefore, we induce access to optimum fabrication condition of memory device application by rf-magnetron sputtering method in this report.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.1
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• pp.136-142
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• 2005

In this paper, we wrote about the basic experimentation of Optical CT's temperature characteristic to measure high-current in a super-high-voltage electric power equipment which is using Faraday effect. We used the 1310[nm] Laser Diode as the light source and PIN Photodiode as receiver. For the transmission line of light, we used 30[m] single mode fiber which could maintain the state of polarization in the optical fiber. For the experiment, the temperature transformation device make by aluminium. the The range of current was from 400[A] and 1300[A] and the range of temperature was from $-40[^{\circ}C]\;to\;50[^{\circ}C]$. In a same experimental condition, magnitude increased input current increase follow by increasing proportion of input current.

• Journal of Advanced Navigation Technology
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• v.21 no.5
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• pp.466-471
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• 2017

SOTM is a device for the satellite communication on the move. Many studies are conducted on microstrip, waveguide and array antenna for the low profile of the SOTM's antenna. But those antennas have a problem that is difficult to adjust the polarization, and for that reason we have studied the parabolic antenna structure. The general form of parabolic reflector structure is circular, but we used cut-off shape reflector by cutting the upper and lower reflector for low profile antenna. Accordingly, this results in the decrease of reflector area which causes reduced gain and G/T ratio. In order to solve this problem, we have transformed and designed the sub reflector for improving the efficiency and gain of the cut- off shape parabolic antenna.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.101-104
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• 1998

We report some methods for measuring a LiNbO$_3$ optical phase modulator bandwidth. Since Mach-Zehnder waveguide type, one of methods for modulation bandwidth measurement, is comparatively simple and useful, it was adapted in this work. In order to confirm this method, the waveguide of single and Mach-Zehnder type were fabricated on the same wafer. The Mach-Zehnder interferometric waveguide and the single channel waveguide were used for the measurement of the phase modulator's driving voltage and bandwidth for device fabrications, respectively. Ti-860$\AA$ in-diffusion was achieved in a wet-bubbling oxygen environment at 105$0^{\circ}C$/8hours. LINbO$_3$ internal chips were pigtailed to PMF(polarization maintaining fiber)/SMF(single mode fiber) using an epoxy curing technique. Examined were optical properties such as an insertion loss, propagation loss and mode size, and the loss mechanism of optical coupling between an optical fiber and a waveguide was considered.

• Korean Journal of Optics and Photonics
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• v.17 no.2
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• pp.181-185
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• 2006

A novel 60GHz optical carrier generator with a polarization domain-inverted structure is suggested and is demonstrated. The two arms of the Mach-Zehnder optical waveguide are periodically poled for quasi-phase velocity matching between the optical wave at 1550nm and the RF wave at 30 GHz. The center frequency of band-pass modulation and the 3 dB bandwidth of the fabricated modulator were measured to be 30.3 GHz and 5.1 GHz, respectively. Sub-carriers with the frequency difference of 60GHz waeregenerated under appropriate DC biac voltage application while the carrier was suppressed to lead to the power ratio between the modulated sub-carrier and the suppressed fundamental carrier of 28 dB, which proves that double sideband- suppressed carrier(DSB-SC) operation can be realized by the suggested single device.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.6
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• pp.465-470
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• 2020

Heterolayered K(Ta,Nb)O₃/Pb(Zr,Ti)O₃ thin films on Pt/Ti/SiO₂/Si substrates were prepared by a sol-gel process and spin-coating method. The structural and electrical properties were measured to investigate the possibility of application as an electrocaloric effect device. All specimens exhibited dense and uniform cross-sectional structures without pores, and the average thickness of the specimen coated six times was approximately 394 nm. Curie temperatures were observed at 5℃ or less in type-I and 10℃ in type-II specimens, respectively. Type-II specimens coated 6 times showed a relative dielectric constant of 758 and remanent polarization of 9.71 μC/㎠ at room temperature. The maximum electrocaloric effect occurred between 20 and 25℃, slightly higher than their Curie temperature, and the electrocaloric property (ΔT) of the type-II specimens coated 6 times was approximately 1.2℃ at room temperature.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.169-170
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• 2006

In this study, ultra thin films of ferroelectric vinylidene fluoride-trifluoroethylene (VF2-TrFE) copolymer were fabricated on degenerated Si (n+, $0.002\;{\Omega}{\cdot}cm$) using by spin coating method. A 1~5 wt% diluted solution of purified vinylidene fluoride-trifluoroethylene (VF2:TrFE=70:30) in a dimethylformamide (DMF) solvent were prepared and deposited on silicon wafers at a spin rate of 2000~5000rpm for 30 seconds. After annealing in a vacuum ambient at $200^{\circ}C$ for 60 min, upper gold electrodes were deposited by vacuum evaporation for electrical measurement. X-ray diffraction results showed that the VF2-TrFE films on Si substrates had $\beta$-phase of copolymer structures. The capacitance on $n^+$-Si(100) wafer showed hysteresis behavior like a butterfly shape and this result indicates clearly that the dielectric films have ferroelectric properties. The typical measured remnant polarization (2Pr) and coercive filed (EC) values measured using a computer controlled a RT-66A standardized ferroelectric test system (Radiant Technologies) were about $0.54\;C/cm^2$ and 172 kV/cm, respectively, in an applied electric field of ${\pm}0.75\;MV/cm$.