• Korean Journal of Optics and Photonics
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• v.14 no.6
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• pp.600-605
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• 2003

We have experimentally demonstrated a Direct Optical Switching (DOS) CDMA for future wide-band mobile communication systems at the 40 ㎓ band by using orthogonal (crosscorrelation $\leq$2) unipolar type codes with code length of 16 and chip rate of 2.5 Gcps for radio-over-fiber (RoF) systems. Pulse-amplitude-equalized 40 ㎓ laser pulses were provided by rational-harmonically mode-locking a 10 ㎓ fiber ring laser.

• Journal of the Institute of Convergence Signal Processing
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• v.10 no.2
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• pp.120-126
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• 2009

There are many different types of surface defects on semiconductor Integrated Chips (IC's) caused by various factors during manufacturing process, such as cracks, foreign materials, chip-outs, chips, and voids. These defects must be detected and classified by an inspection system for productivity improvement and effective process control. Among defects, in particular, foreign materials and chips are the most difficult ones to classify accurately. A vision system composed of a carefully designed optical system and a processing algorithm is proposed to detect and classify the defects on QFN(Quad Flat No-leads) packages. The processing algorithm uses features derived from the defect's position and brightness value in the Maximum Likelihood classifier and the optical system is designed to effectively extract the features used in the classifier. In experiments we confirm that this method gives more effective result in classifying foreign materials and chips.

• Journal of the Korean Physical Society
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• v.73 no.9
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• pp.1346-1350
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• 2018

An electrode-evaporation technology on both the top and bottom sides of the bare vertical-type single chip separated from the traditional substrate by cooling, was developed for III-nitride vertical-type single chip LEDs with thick GaN epilayer. The post-process of the cooling step was followed by sorting the bare vertical-type single chip LEDs into the holes in a pocket-type shadow mask for deposition of the electrodes at the top and bottom sides of bare vertical-type single chip LEDs without the traditional substrate for electrode evaporation technology for vertical-type single chip LEDs. The variation in size of the hole between the designed shadow mask and the deposited electrodes owing to the use of the designed pocket-type shadow mask is investigated. Furthermore, the electrical and the optical properties of bare vertical-type single chip LEDs deposited with two different shapes of n-type electrodes using the pocket-type shadow mask are investigated to explore the possibility of the e-beam evaporation method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.7
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• pp.1347-1353
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• 2015

We implemented a 10 Gb/s 4-channel vertical cavity surface emission lasers (VCSEL) driver array in a $0.13{\mu}m$ CMOS process technology. To enhance high current resolution, power dissipation, and chip space area, digital APC/AMC with time division sensing technology is primarily adopted. The measured -3 dB frequency bandwidth is 9.2 GHz; the small signal gain is 10.5 dB; the current resolution is 0.01 mA/step, suitable for the wavelength operation up to 10 Gb/s over a wide temperature range. The proposed APC and AMC demonstrate 5 to 20 mA of bias current control and 5 to 20 mA of modulation current control. The whole chip consumes 371 mW of low power under the maximum modulation and bias currents. The active chip size is $3.71{\times}1.3mm^2$.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.7
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• pp.40-48
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• 2015

An optical network-on-chip(ONoC) architecture is emerging as a new paradigm for solving on-chip communication bottleneck. Recent studies on ONoC have been focusing on supporting the parallel transmission and avoiding path collisions using wavelength division multiplexing(WDM). However, since the maximum number of wavelengths, which a single waveguide can accommodate is limited by crosstalk and insertion loss. Therefore previous WDM studies based on incrementing the number of different wavelengths according to the number of nodes would be infeasible due to the implementation complexity. To solve such problems, we combined time division multiplexing(TDM) and wavelength-routed ONoC, along with an optimized channel allocation algorithm, which can minimize the number of extra wavelength channels and latency caused by combining TDM scheme.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.6
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• pp.472-476
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• 2019

We have proposed a novel planar lightwave circuit (PLC) optical sensor to monitor the contamination in a flow-cell where water is continuously supplied through a water quality measurement system. We designed a PLC chip with a V-shape waveguide and the simulated its function as a sensor for monitoring contamination in a flow-cell using a numerical the FDTD (finite-difference time-domain) analysis. A novel cross type of waveguide was introduced to make the PLC chip of the V-shaped waveguide. The fabricated PLC was cut into the cross waveguide. A change in the optical propagation loss of the PLC sensor was observed after immersing the PLC sensor into city water. It was determined that the propagation loss of the PLC sensor was 3 dB at a wavelength of $1.55{\mu}m$ in the city water for 15 days.

• Proceedings of the Optical Society of Korea Conference
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• 2002.07a
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• pp.172-173
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• 2002

As feature sizes of circuits and devices approach 100 m and chip frequencies climb into the upper gigahertz to terahertz range, it becomes increasingly important to have a convenient method of characterizing properties of thin dielectric films in the GHz to THz frequency range [1]. To measure the dielectric and optical properties of materials at THz frequency, a TH2 time-domain spectroscopy has been utilized during past decade. (중략)

• Korean Journal of Optics and Photonics
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• v.10 no.6
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• pp.500-506
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• 1999

We designed and fabricated a bidirectional optical transceiver module for low cost access network. An integrated chip forming a pin-PD on an 1.3 urn FP-LD was assembled by flip-chip bonding on a Si optical bench, a single mode fiber with an angled end facet was aligned passively with the integrated chip on V-groove of Si-optical bench. Gaussian beam theory was applied to evaluate the coupling coefficients as a function of some parameters such as alignment distance, angle of fiber end facet, vertical alignment error. The theory is also used to search the bottle-neck between transmittance and receiving coupling efficiency in the bi-directional optical system. Tn this paper, we confirmed that reduction of coupling efficiency by the vertical alignment error between laser beam and fiber core axis can be compensated by controlling the fiber facet angle. In the fabrication of sub-module, a'||'&'||' we made such that the fiber facet have a corn shape with an angled facet only core part, the reflection of transmitted laser beam from the fiber facet could be minimized below -35 dE in alignment distance of 2: 30 /J.m. In the same condition, transmitted output power of -12.1 dEm and responsivity of 0.2. AIW were obtained.

• Proceedings of the Optical Society of Korea Conference
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• 1990.02a
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• pp.79-81
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• 1990

Temperature distribution of laser diode chip mounted on ideal heat kink was calculated by numerical analysis. In numerical analysis, infinite difference method and Gauss-Scidel iteration was adopted on the basis of two dimensional heat conduction phenomena. As a result, temperature increase of active medium of laser diode driven at 60mA was calculated to be 1.47$^{\circ}C$

• Proceedings of the Optical Society of Korea Conference
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• 2005.07a
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• pp.306-307
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• 2005