• Journal of the Optical Society of Korea
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• v.11 no.1
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• pp.10-17
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• 2007

We need two operation modes to obtain the complex hologram without bias and the conjugate image in the modified triangular interferometer (MTI). To solve the problem, we proposed the optimized MTI with one wave plate, which can obtain cosine and sine functions by the combination of one wave plate and one linear polarizer. In the extraction of phase term using the combination of polarization components, the phase error occurs, and we analyzed such potential phase errors in the optimized MTI.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.04b
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• pp.105-108
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• 2002

We report on the polarization-insensitive design and fabrication of an arrayed waveguide gratings (AWG's) using sol-gel derived silica glass films formed on fused silica substrates to provide cheap and stable tools for better design. An arrayed-waveguide grating multiplexer with raised structure is fabricated in order to effect polarization sensitivity. Since polarization is usually not known after propagation in an optical fiber. passive WDM components such as monolithic wavelength demultiplexer have to be polarization insensitive. Here, we observed that polarization have effect on crosstalk of output spectrum in arrayed-waveguide grating

• ETRI Journal
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• v.38 no.5
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• pp.981-987
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• 2016

We present a cost-effective dual polarization quadrature phase-shift coherent receiver module using a silica planar lightwave circuit (PLC) hybrid assembly. Two polarization beam splitters and two $90^{\circ}$ optical hybrids are monolithically integrated in one silica PLC chip with an index contrast of $2%-{\Delta}$. Two four-channel spot-size converter integrated waveguide-photodetector (PD) arrays are bonded on PD carriers for transverse-electric/transverse-magnetic polarization, and butt-coupled to a polished facet of the PLC using a simple chip-to-chip bonding method. Instead of a ceramic sub-mount, a low-cost printed circuit board is applied in the module. A stepped CuW block is used to dissipate the heat generated from trans-impedance amplifiers and to vertically align RF transmission lines. The fabricated coherent receiver shows a 3-dB bandwidth of 26 GHz and a common mode rejection ratio of 16 dB at 22 GHz for a local oscillator optical input. A bit error rate of $8.3{\times}10^{-11}$ is achieved at a 112-Gbps back-to-back transmission with off-line digital signal processing.

• Current Optics and Photonics
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• v.1 no.4
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• pp.396-401
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• 2017

In this article, we proposed hybrid polarization singularity configurations, based on the superposition of two orthogonal circularly polarized components, one of which is a light beam with two optical vortices. The topological configurations are the hybridization of lowest-order polarization singularities, but are different from high-order polarization singularities. Our numerical simulation may provide a theoretical basis for expanding the variety of polarization singularity configuration.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.3
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• pp.10-18
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• 2003

In this paper, we propose an optical encryption system based on the encryption of information using the phase component of a wavefront and orthogonal polarization in a Mach-Zehnder interferometer. Since the incoherence of the two perpendicularly polarized lights removes interference component, the decrypted image is stable. In encryption process, the original image is converted into an image having random polarization state by the relative phase difference of horizontal polarization and vertical polarization, so we cannot obtain the original information from the random polarization distribution. To decrypt an Image, the random polarization distribution of encrypted image is divided into two orthogonal components, then key image must be placed on vertical path of Mach-Zehnder interferometer. The decrypted image is obtained In the form of intensity by use of an analyzer.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.8 s.251
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• pp.965-975
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• 2006

High pressure turbine blades are one of the key components in fossil power plants operated at high temperature. The blade is usually made of 12Cr steel and its operating temperature is above $500^{\circ}C$. Long term service at this temperature causes material degradation accompanied by changes in microstructures and mechanical properties such as strength and toughness. Quantitative assessment of reduction of strength and toughness due to high temperature material degradation is required for residual life assessment of the blade components. Nondestructive technique is preferred. So far most of the research of this kind was conducted with low alloy steels such as carbon steel, 1.25Cr0.5Mo steel or 2.25Cr1Mo steel. High alloy steel was not investigated. In this study one of the high Cr steel, 12Cr steel, was selected for high temperature material degradation. Electrochemical polarization method was employed to measure degradation. Strength reduction of the 12Cr steel was represented by hardness and toughness reduction was represented by change of transition temperature, FATT. Empirical relationships between the electrochemical polarization parameter and significance of material degradation were established. These relationship can be used for assessing the strength and toughness on the aged high pressure blade components indirectly by using the electrochemical method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.7
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• pp.1241-1249
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• 2002

The extent of materials deterioration can be evaluated accurately by mechanical test such as impact test or creep test. But it is almost impossible to extract a large test specimen from in-service components. Thus material degradation evaluation by non-destructive method is earnestly required. In this paper, the material degradation for virgin and several aged materials of a Cr-Mo-V steel, which is an candidated as structural material of the turbine casing components for electric power plant, is nondestructively evaluated by reactivation polarization testing method. And, the results obtained from the test are compared with those in small punch(SP) tests recommended as a semi-nondestructive testing method using miniaturized specimen. In contrast to the aged materials up to 1,000hrs which exhibit the degradation behaviors with increased ${\Delta}[DBTT]_{SP}$, the improvement of mechanical property can be observed on the 2,000hrs and 3,000hrs aged materials. This is because of the softening of material due to the carbide precipitation, the increase of ferritic structures and the recovery of dislocation microstructure by long-time heat treatment. The reactivation rates($I_R/I_{Crit},\;Q_R/Q_{Crit}$) calculated by reactivation current densityt ($I_R$) and charge($Q_R$) in the polarization curves exhibit a good correlation with ${\Delta}[DBTT]_{SP}$ behaviors.

• Journal of Communications and Networks
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• v.8 no.3
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• pp.286-289
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• 2006

Measurement results are presented for the effects of people moving near and across short-range indoor propagation links at 2.45 GHz (ISM band). Excess loss due to scattering and blockage by human bodies in the vicinity of one terminal were measured for different radio links in an office environment. Statistics on fades due to human body motion are given. Polarization coupling (depolarization) for various radio links was measured, and correlation of polarization components is discussed as a basis for using polarization diversity reception in short-range indoor systems.

• Korean Journal of Optics and Photonics
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• v.8 no.6
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• pp.486-491
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• 1997

A division-of-amplitude type photopolarimeter has been constructed for the analysis of the dynamic optical characteristics of liquid crystal panels, one of the essential components of liquid crystal displays. In this instrument an incoming light ray, whose state of polarization is to be determined, is divided into three rays of nearly same intensities and of identical polarization state by using NPBS'(non-polarizing beam splitters). Each of the three rays is further divided into two components of orthogonal polarization states by using a PBS(polarizing cube beamsplitter) or by using a combination of a quater wave plate followed by a PBS. The intensity of each ray is measured by using a photodiode to produce a set of six photo-signals, which in turn are converted into four Stokes parameters describing the state of polarization of the incoming ray. Performance test of the insrument shows that its time resolution is 80 $mutextrm{s}$, accuracy $\pm$0.3 degrees when the state of polarization of the incoming ray is representated on the Poincare sphere.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.6 s.177
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• pp.1398-1407
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• 2000

The structural steels of power plant show the decrease of mechanical properties due to degradation such as temper embrittlement, creep damage and softening during long-term operation at high temper ature. The typical causes of material degradation damage are the creation and coarsening of carbides(M23C6, M6C) and the segregation of impurities(P, Sb and Sn) to grain boundary. It is also well known that material degradation induces the cleavage fracture and increases the ductile-brittle transition temperature of steels. So, it is very important to evaluate degradation damage to secure the reliable and efficient service condition and to prevent brittle failure in service. However, it would not be appropriate to sample a large test piece from in-service components. Therefore, it is necessary to develop a couple of new approaches to the non-destructive estimation technique which may be applicable to assessing the material degradation of the components with not to influence their essential strength. The purpose of this study is to propose and establish a new electrochemical technique for non-destructive evaluation of material degradation damage for Cr-Mo steels which is widely used in the high temperature structural components. And the electrochemical anodic polarization test results are compared with those of semi-nondestructive SP test.