• 제목/요약/키워드: Photorefractive

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Parametric Instability Boundaries for Spatial Subharmonics in Photorefractive Moving Gratings: Theory and Experiments

  • Kwak, Chong-Hoon;Lee, El-Hang
    • ETRI Journal
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    • 제16권4호
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    • pp.13-25
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    • 1995
  • We have derived a nonlinear spatiotemporal differential equation for space-charge fields from Kukhtarev’s material equations in a moving coordinate system and obtained the spatial subharmonic instability boundaries by using linear stability analysis. It is also found that there is an analogy between the temporal subharmonic and the spatial subharmonc instabilities in the sense that the governing differential equations describing the instability boundaries are formally identical. The experiments for generating spatial subharmonic waves are performed in a photorefractive $Bi_{12}SiO_{20}$ crystal by using conventional moving grating technique. The threshold detunings are experimentally determined and the results are compared with the theory.

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열고정에 의한 광굴절 LiNbO$_3$결정에서의 굴절률 역전 (The reversal of photorefractive index in LiNbO$_3$ by thermal fixing)

  • 박남기;김경염;양병춘;이병호
    • 한국광학회:학술대회논문집
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    • 한국광학회 2000년도 제11회 정기총회 및 00년 동계학술발표회 논문집
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    • pp.286-287
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    • 2000
  • 최근에 광연결(optical interconnection)을 위한 목적으로 LiNbO$_3$(0.03 mol% Fe doped)결정에 광굴절(photorefractive) 도파로를 기록하는 방법이 소개되고$^{(1-2)}$ 있는데 제작 방법과 원리는 다음과 같다. 17mW 출력의 He-Ne 레이저광을 렌즈로 통과시켜 빔의 크기를 줄인 후 초점은 LiNbO$_3$크리스털에 입사하는 반대편 면에 맞추어 입사시킨다. 그림 1에서 +y방향으로 초점이 입사면을 통과할 때까지 크리스털을 이동시켜 도파로를 만든다. 이 때 이동하는 방법은 10ms 노광시킨 후 15$mu extrm{m}$씩 불연속적으로 움직여 나간다. (중략)

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Photorefractive Performance of Poly[methyl-3-(9-carbazolyl) propylsiloxane] Based Composites Sensitized with Poly(3-hexylthiophene) in a 0.2-1wt % Range

  • Oh, Jin-Woo;Kim, Nak-Joong
    • Bulletin of the Korean Chemical Society
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    • 제31권1호
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    • pp.41-46
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    • 2010
  • In this work, we report on the characterization of six low-$T_g$ poly[methyl-3-(9-carbazolyl) propylsiloxane] based photorefractive (PR) composites sensitized with poly(3-hexylthiophene) (P3HT) in different concentrations, ranging from 0.2 to 1 wt %. At 632.8 nm, photoconductivity, space charge field, refractive index modulation, and grating buildup time were measured versus external electric field. The photoconductivity was strongly dependent on the visible light absorption and mobility. The magnitude of space charge field was affected by the conductivity contrast $\sigma_{ph}/(\sigma_{ph}+\sigma_d)$. The refractive index modulation increased with the magnitude of space charge field and the PR grating buildup speed increased with the photoconductivity.

A.C. 전장이 인가된 광굴절 Bi12SiO20 결정의 2광파 혼합 이득의 시간종속 변화 (Transient Behaviour of Photorefractive $Bi_{12}SiO_{20}$ Crystal: Two Wave Mixing with an External A.C. Field)

  • 곽종훈
    • 한국광학회지
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    • 제4권1호
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    • pp.73-83
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    • 1993
  • 광굴절결정에 구형과 및 저현파형의 외부 전장을 인가할 때 유기되는 공간 전하장의 시간 종속 해를 해석적으로 유도하였다. B$i_{12}$Si$O_{20}$ 결정에 최대 7KV/cm (주파수<1KHz)의 전장을 가하면서 시간 종속적인 2광파 혼합의 이득 변화를 측정하고 이론치와 정량적으로 비교 분석하였다.

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Power Characteristics of cw Second-harmonic Generation in Periodically Poled LiNbO3

  • Kang, Bong-Hoon;Joo, Gi-Tae;Rhee, Bum-Ku
    • 한국세라믹학회지
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    • 제47권5호
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    • pp.430-432
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    • 2010
  • We verified through a noncritical phase-matched second-harmonic generation experiment that the periodically-poled $LiNbO_3$ (PPLN) had a large effective nonlinear optical coefficient, demonstrating that the QPM grating was uniform throughout the entire length of PPLN. The quasi-phase matching temperature was $193.4^{\circ}C$. The maximum SHG output power at the fundamental power of 2.0 W was found to be 18.0 mW; generated second-harmonic beam was found to have no photorefractive effect.