• 한국광학회지
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• 제4권3호
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• pp.323-329
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• 1993

본 논문에서는 광굴절 특성을 나타내는 파라메타중 회절효율의 전도도비(${\sigma}_d$/{\sigma}_p$) 의존성에 관해 연구 하였다. 전도도비는 입사빔의 세기에 의존하며, 암전도도 ${\sigma}_d$가 광전도도 ${\sigma}_p$ 에 비해 무시할 수 없을 때 입사빔의 세기에 따라 전도도비가 변화되고, 전도도비의 변화는 결정 내의 정전기장에 영향을 주게 된다. 정전기장의 변화는 전기광학효과에 의해 굴절율을 변화시키고, 굴절율의 변화는 회절효율과 관계한다. 개방회로 상태에서 0.1%/mole $Fe:LiNbO_3$ 결정과 $LiNbO_3$ 웨이퍼에 Fe를 증착시킨 LiNb$O_3$에서 두 입사빔의 세기비와 입사빔세기의 합을 다르게 할 때 회절효율을 측정하고 이론값과 비교하였다.

• 한국재료학회지
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• 제12권4호
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• pp.254-258
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• 2002

To realize channel cross-connecting in optical communications systems, a high speed optical matrix switch was fabricated using z-cut $LiNbO_3$. For switch fabrication was design bending structure and coupling length and four $2{\times}2$ directional couplers were integrated on one substrate far construction of a $4{\times}4$ switch. Single-mode optical waveguides were formed by Ti-diffusion at a wet $O_2$ atmosphere. Ti-diffusion profile, refractive index variation and waveguide morphology were analyzed by Prism coupler and optical microscopy, respectively.

• E2M - 전기 전자와 첨단 소재
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• 제8권2호
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• pp.190-195
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• 1995

Temperature dependences of the dielectric constant K(T), remanent polarization $P_{r}$, (T), effective birefringence overbar .DELTA.n(T), transmitted light intensity and quadratic electro optic coefficient R(T) of the two-stage sintered xBa(L $a_{1}$2/N $b_{1}$2/) $O_{3}$-(1-x)Pb(Z $r_{y}$ $Ti_{1-y}$) $O_{3}$(x=0.085, 0.09, 0.40.leq.y.leq.0.70) ceramics were investigated. Increasing the PbZr $O_{3}$ contents, the crystal structure of a specimen was changed from a tetragonal phase to a rhombohedral and cubic phase, and the phase transition was showed a diffuse phase transition(DPT) characteristics. In the compositions which located on the PE-FE phase boundary, the discrepancy was observed between the Curie temperature and temperature which a microscopic polarization and effective birefringence were disappeared.red.d.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 춘계학술대회 논문집 유기절연재료 전자세라믹 방전플라즈마 연구회
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• pp.189-192
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• 2001

In this paper, an novel optical measuring system based on the electro-optic effect has been proposed and realized using Pockels cell with a view to detecting partial discharge taking place at the needle plane electrode. This system has the following advantages ; nonmetallic probe sensor, immune to external EMI noise and broad band response of the Pockels cell from DC to GHz. This system is constructed by He-Ne laser, Mach-Zehnder interferometer with Pockels sensor, balanced photo receiver, data acquisition board and PC. The response characteristics of the developed proto type sensor are examined for AC and corona discharge.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 제5회 영호남 학술대회 논문집
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• pp.98-102
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• 2003

$Ba_2NaNb_5O_{15}$, hereafter BNN, thin films are attractive candidates for nonvolatile memory and electro-optic devices. In the present work, thin films that have different contents of Ba, Na and Nb have been prepared by H-MOD technique on silicon and Pt substrates. XRD and SEM were used to investigate the phase evolution behavior and the microstructure of the films. It was found that the films of about 450nm thick were crack-free and uniform in microstructure. Nb content strongly influenced the phase formation of the films, where low temperature phase was always formed at the stoichiometric BNN composition. However, the amount of low temperature phase decreased with the increase of excess Nb content, and the single phase (orthorhombic tungsten bronze structure) BNN thin film was obtained at the temperature as low as $750^{\circ}C$ for samples with excess niobium. From this study, the sub-solidus phase diagram below $850^{\circ}C$ for $BaO-Na_2O-Nb_2O_5$ ternary system is proposed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 E
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• pp.1705-1707
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• 1997

In this work, a possible new PD de technique, based on the electro-optic effect(P effect), has been proposed. The refractive index ellipsoid of EO crystal, as $LiNbO_3$, is changed by both the externally a electric field and its hysteresis loop of which effect on this hysteresis loop gives rise t discrepancy of index variation. Therefore, an eq regarding the phase variation of modulated beam through $LiNbO_3$ crystal under applied e field, is newly proposed considering the influen hysteresis characteristics. For this purpose generated from needle-plane electrode in oil has detected by use of $LiNbO_3$ cell and analyzed b equation. As a result, it is observed that PD measu phase intervals are limited by the cr characteristics such as asymmertrical P-E hyst and half-wave voltage.

• Smart Structures and Systems
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• 제6권3호
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• pp.239-262
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• 2010

Tube Lines has carried out a "knowledge and investigation programme" on the deep tube tunnels comprising the Jubilee, Northern and Piccadilly lines, as required by the PPP contract with London Underground. Many of the tunnels have been in use for over 100 years, so this assessment was considered essential to the future safe functioning of the system. This programme has involved a number of generic investigations which guide the assessment methodology and the analysis of some 5,000 individual structures. A significant amount of investigation has been carried out, including ultrasonic thickness measurement, detection of brickwork laminations using radar, stress measurement using magnetic techniques, determination of soil parameters using CPT, pressuremeter and laboratory testing, installation of piezometers, material and tunnel segment testing, and trialling of remote photographic techniques for inspection of large tunnels and shafts. Vibrating wire, potentiometer, electro level, optical and fibre-optic monitoring has been used, and laser measurement and laser scanning has been employed to measure tunnel circularity. It is considered that there is scope for considerable improvements in non-destructive testing technology for structural assessment in particular, and some ideas are offered as a "wish-list". Assessment reports have now been produced for all assets forming Tube Lines' deep tube tunnel network. For assets which are non-compliant with London Underground standards, the risk to the operating railway has to be maintained as low as reasonably practicable (ALARP) using enhanced inspection and monitoring, or repair where required. Monitoring techniques have developed greatly during recent years and further advances will continue to support the economic whole life asset management of infrastructure networks.

• Macromolecular Research
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• 제15권2호
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• pp.114-128
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• 2007

Polyimides are one of the most important classes of polymers used in the microelectronics and photoelectronics industries. Because of their high thermal stability, chemical resistance, and good mechanical and electric properties, polyimides are often applied in photoresists, passivation and dielectric films, soft print circuit boards, and alignment films within displays. Recently, fully aliphatic and alicyclic polyimides have found applications as optoelectronics and inter layer dielectric materials, due to their good transparencies and low dielectric constants $(\varepsilon)$. The low molecular density, polarity and rare probability of forming inter- or intra-molecular charge transfers, resulting in lowering of the dielectric constant and high transparency, are the most striking characteristics of aliphatic polyimide. However, the ultimate end use of polyimides derived from aliphatic monomers is in their targeted applications that need less stringent thermal requirements. Much research effort has been exerted in the development of aliphatic polyimide with increased thermal and mechanical stabilities, while maintaining their transparencies and low dielectric constants, by the incorporation of rigid moieties. In this article, the recent research process in synthesizing fully aliphatic polyimides, with improved dimensional stability, high transparency and low $\delta$values, as well as the characterizations and future scope for their application in micro electric and photo-electronic industries, is reviewed.

• Bulletin of the Korean Chemical Society
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• 제24권12호
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• pp.1793-1798
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• 2003

A series of amorphous molecules that possess both photoconductive and electro-optic properties was synthesized in order to investigate photorefractive properties of bifunctional organic-glasses. Diethylaminobenzaldehyde-diphenylhydrazone was covalently attached to 5-(4-diethylamino-benzylidene)-1,3-dimethylpyrimidine-2,4,6-trione through a flexible alkyl chain (3, 4, 5, 6 and 10 carbons) containing two ether linkages. The longer linkage not only lowered the glass transition temperature ($T_g$) of the molecules, but also allowed faster orientation of the chromophore. To examine the photorefractive properties, a 50 ${\mu}$m-thick film was prepared from the mixture of a bifunctional molecule, butyl benzyl phthalate, and $C_{60}$. The photoconductivity of this composite was as high as $8.01\;{\times}\;10^{-12}$ S/cm at 60 V/ ${\mu}$m, and the maximum diffraction efficiency ( ${\eta}_{max}$) of 50 ${\mu}$m-thick film was about 5% at 80 V/ ${\mu}$m.

• Bulletin of the Korean Chemical Society
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• 제31권6호
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• pp.1509-1514
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• 2010

Methyl 3,4-di-(2'-hydroxyethoxy)benzylidenecyanoacetate (3) was prepared and condensed with terephthaloyl chloride to yield novel Y-type polyester (4) containing 3,4-dioxybenzylidenecyanoacetate groups as NLO-chromophores, which constituted parts of the polymer main chains. The resulting polymer 4 is soluble in common organic solvents such as acetone and N,N-dimethylformamide. Polymer 4 shows thermal stability up to $280^{\circ}C$ in thermogravimetric analysis with glass-transition temperature obtained from differential scanning calorimetry near $105^{\circ}C$. The second harmonic generation (SHG) coefficient ($d_{33}$) of poled polymer films at the 1064 nm fundamental wavelength is around 2.42 pm/V. The dipole alignment exhibits high thermal stability up to near $T_g$, and there is no SHG decay below $100^{\circ}C$ due to the partial main-chain character of polymer structure, which is acceptable for NLO device applications.