• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.9
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• pp.666-672
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• 2003

In this paper, we described the fabrication and the performance of wavelength tunable distributed bragg reflector (DBR) laser diode (LD), having different waveguide coupling mechanisms; integrated-twin-guide (ITG) DBR-LD and butt coupled (BT) DBR-LD. This deviceis fabricated by metal organic vapor phase epitaxy (MOVPE) growth and planar buried heterostructure (PBH)-type transverse current confinement structure. The result of measurement, the optical performance of BT-DBR-LD is better over 2 times than that of ITG-DBR-LD at the variation of threshold current and output power, and slop efficiency due to the higher coupling efficiency of the butt coupled structure than the integrated twin guide structure. The maximum wavelength tuning range is about 7.2nm for ITG DBR-LD and 7.4nm for BT DBR-LD. Both types of lasers have a very high yield of single mode operation with a side-mode suppression ratio of more than 35dB.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.10
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• pp.2935-2944
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• 2009

This paper proposes Dual DBR(Drum-Buffer-Rope) system for a small-to-medium-sized PCB(Printed Circuit Board) manufacturing line. DBR method of TOC(Theory of Constraints) is an effective system for a small-to-medium-sized company to build production scheduling system. But to apply it to PCB line, it needs more technical consideration because of multiple constraints, looping process line and complex buffer management. This paper proposes an answer of these problems using Dual DBR to build production scheduling system more successfully. And it was confirmed that lead time was reduced more than 20% applying Dual DBR system to a domestic PCB manufacturing line actually.

• Journal of the Korea Society for Simulation
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• v.21 no.4
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• pp.11-24
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• 2012

We compared a DBR(drum-buffer-rope) system with a CONWIP(constant work-in-process) system in a production line with constant processing times. Based on the observation that a WIP-controlled line production system such as DBR and CONWIP is equivalent to a m-node tandem queue with finite buffer, we applied a max-plus algebra based solution method for the tandem queue to evaluate the performance of two systems. Numerical examples with 6 workstations were also used to demonstrate the proposed analysis. The mathematical analyses support that CONWIP outperforms DBR in terms of expected waiting time and WIP. Unlike the CONWIP case, sequencing workstations in a DBR affects the performance of the system. Delaying a bottleneck station in a DBR reduces expected waiting time.

• Journal of Integrative Natural Science
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• v.2 no.4
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• pp.275-279
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• 2009

Recently, number of studies for porous silicon (PSi) have been investigated by many researchers. Multistructured porous silicon such as a distributed Bragg reflector (DBR) PSi, has been a topic of interest, because of its unique optical properties. DBR PSi were prepared by using an electrochemical etch of $P{^+}{^+}$-type silicon wafer with resistivity between 0.1 and $10m{\Omega}cm$. The electrochemical etch with square wave current density results in two different refractive indices in the porous layer. In this work, DBR porous silicon chips for a simple and portable organic vapor-sensing device have fabricated. The optical characteristics of DBR PSi have been investigated. DBR porous silicon have been characterized by FT-IR and Ocean optics 2000 spectrometer. The device used DBR PSi chip has been demonstrated as an excellent gas sensor, showing a great senstivity to organic vapor at room temperature.

• Journal of Integrative Natural Science
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• v.8 no.1
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• pp.67-74
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• 2015

Sensing characteristics for porous smart particle based on DBR smart particles were reported. Optically encoded porous silicon smart particles were successfully fabricated from the free-standing porous silicon thin films using ultrasono-method. DBR PSi was prepared by an electrochemical etch of heavily doped $p^{++}$-type silicon wafer. DBR PSi was prepared by using a periodic pseudo-square wave current. The surface-modified DBR PSi was prepared by either thermal oxidation or thermal hydrosilylation. Free-standing DBR PSi films were generated by lift-off from the silicon wafer substrate using an electropolishing current. Free-standing DBR PSi films were ultrasonicated to create DBR-structured porous smart particles. Three different surface-modified DBR smart particles have been prepared and used for sensing volatile organic vapors. For different types of surface-modified DBR smart particles, the shift of reflectivity mainly depends on the vapor pressure of analyte even though the surfaces of DBR smart particles are different. However huge difference in the shift of reflectivity depending on the different types of surface-modified DBR smart particles was obtained when the vapor pressures are quite similar which demonstrate a possible sensing application to specify the volatile organic vapors.

• Journal of Integrative Natural Science
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• v.3 no.2
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• pp.78-83
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• 2010

DBR/Host dual porous silicons containing DBR and host structure were prepared and their optical properties were characterized using Ocean Optics spectrometer. In this dual porous silicon, single porous silicon layer was used as host layer for possible biomolecule and drug materials and DBR porous silicon layer was used for signal transduction due to the recognition of molecules. Optical reflection spectrum of dual porous silicon displayed only DBR reflection but Fabry-Perot fringe pattern. DBR reflection band of dual porous silicon shifted to the shorter wavelength as the etching time of host layer increased. Cross-sectional FE-SEM image of dual porous silicon displayed a thickness of about 20 micrometer for DBR porous silicon layer. Developed etching technology could be useful to prepare DBR porous silicon which exhibited specific reflection resonance at the required wavelength and to provide an label-free biosensors and drug delivery materials.

• Journal of Integrative Natural Science
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• v.2 no.2
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• pp.82-85
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• 2009

Distributed Bragg reflector (DBR) porous silicon (PSi) was generated by an electrochemical etching a bragg structure into a silicon wafer through electrode current in aqueous ethanolic HF solution. DBR PSi exhibiting unique reflectivity was successfully obtained by an electrochemical etching of silicon wafer using square current waveform. The multilayered photonic crystals of DBR PSi exhibited the reflection of a specific wavelength with high reflectivity in the optical reflectivity spectrum. In this work, we have developed a method to create refractive index in Si substrate through intensity of an electric current. The electrochemical process allows for precise control of the structural properties of DBR PSi such as thickness of the porous layer, porosity, and average pore diameter. The number of reflection peak of DBR PSi and its pore size increased as the intensity of electric current increased. This might be a demonstration for the fabrication of specific reflectors or filters.

• Korean Journal of Optics and Photonics
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• v.14 no.3
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• pp.327-330
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• 2003

We present the fabrication and measured performance of a wavelength tunable Butt coupled DBR-LD. An average coupling efficiency between active layer and passive waveguide layer was measured over 85％per facet, and the average threshold current was 21 ㎃ for the waveguide integrated DBR laser. High output power of Butt coupled DBR-LD was obtained over 25 ㎽. As high as 25 ㎽ of output power was achieved by the butt coupled method. The maximum wavelength tuning range is about 7.4 nm, and the side mode suppression ratio was more than 40 ㏈ using 1.3 ${\mu}{\textrm}{m}$ InGaAsP waveguide layer.

• Journal of the Korean Vacuum Society
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• v.16 no.3
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• pp.221-226
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• 2007

DBR (distributed Bragg reflectors) PSi (porous silicon) composite films displaying dual optical properties, both optical reflectivity and photoluminescence had been developed. DBR PSi samples were prepared by electrochemical etch of heavily doped $p^{++}-type$ silicon wafers (boron doped, polished on the <100> face, resistivity of $0.8-1.2m{\Omega}-cm$, Siltronix, Inc.). Free-standing DBR PSi films were treated with PMMA (polymethyl methacrylate) to produce flexible, stable composite materials in which the PSi matrix is covered with PMMA containing photoluminescent polysiloles. Optical characteristics of DBR PSi/polysilole-impregnated PMMA composite materials exhibit both their photonic reflectivity at 565 nm and photoluminescence at 510 nm, simultaneously. A possible application of this materials will be discussed.

• Journal of the Korean Vacuum Society
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• v.15 no.3
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• pp.280-286
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• 2006

A distributed Bragg reflector (DBR) for the application of $1.3{\mu}m$ vertical cavity surface emitting laser (VCSEL) has grown by digital-alloy AlGaAs layer using the molecular beam epitaxy (MBE) method. The measured reflection spectra of the digital-alloy AlGaAs/GaAs DBR have uniformity in 0.35% over the 1/4 of 3-inch wafer. Furthermore, the TEM image showed that the composition and the thickness of the digital-alloy AlGaAs layer in AlGaAs/GaAs DBR was not affected by the temperature distribution over the wafer whole surface. Therefore, the digital-alloy AlGaAs/GaAs DBR can be used to get higher yield of VCSEL with the active medium of InAs quantum dots whose gain is inhomogeneously broadened.