• Title/Summary/Keyword: Periodic poling

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Effective Periodic Poling in Optical Fibers

  • Kim, Jong-Bae;Ju, Jung-Jin;Kim, Min-Su;Seo, Hong-Seok
    • ETRI Journal
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    • v.26 no.3
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    • pp.277-280
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    • 2004
  • The distributions of electric field and induced second-order nonlinearity are analyzed in the periodic poling of optical fibers. A quasi-phase matching efficiency for the induced nonlinearity is calculated in terms of both the electrode separation distance between the applied voltage and generalized electrode width for the periodic poling. Our analysis of the quasi-phase matching efficiency implies that the conversion efficiency can be enhanced through adjusting the separation distance, and the electrode width can be maximized if the electrode width is optimized.

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Periodically Poled $KNbO_3$ Crystals for Quasi-Phase-Matching

  • Kim, Joong-Hyun;Lee, Sooseok;Yoon, Choon-Sup
    • Proceedings of the Korea Crystallographic Association Conference
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    • 2002.11a
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    • pp.18-18
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    • 2002
  • Although it was suggested in 1962 that an efficient wavelength conversion could be achieved using ferroelectric crystals of periodic 180° domains, it was not until 1990's that quasi-phase-matching (QPM) became realized, as technology for periodic poling of LiNbO₃ crystals was readily available. Since ferroelectric domain inversion brings about change of the sign of second-order nonlinear susceptibility, periodically poled ferroelectric structures provide an ideal way of achieving QPM for second-harmonic generation and optical parametric oscillation. Periodically poled ferroelectric domains can also be utilized for optical devices, such as Brags electrooptic modulators. fabrication of stable periodic domain structures depends on a number of poling parameters of a ferroelectric crystal, such as coercive field, internal field and electrical conductivity. We present poling kinetics of KNbO₃ crystals, which involve domain nucleation and growth, backswitching, relaxation of internal field. Optimum poling conditions were established by designing a proper wave shape of external field. We demonstrate an efficient second-harmonic generation using QPM in a periodically poled KNbO₃ crystal.

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A study on the fabrication of periodically poled Ti:LiNbO3 (PPLN) by the control of charge (전하량제어에 의한 주기적 분극반전 Ti:LiNbO3 (PPLN) 제작 공정에 관한 연구)

  • Kim, Won-Joung;Jung, Hong-Sik;Lee, Han-Young
    • Korean Journal of Optics and Photonics
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    • v.16 no.4
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    • pp.366-375
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    • 2005
  • A fabrication process of periodic electric field assisted poling of Ti-diffused channel waveguides in LiNbO3 (Ti:PPLN) has been developed and improved using a periodic 180o phase inversion along the z-axis. The zig for poling inversion and the Labview program of charge control have been devised. Pulse high voltage and duty cycle were adjusted based on the estimated charge required for poling inversion. Monitoring the change of leakage current under applied voltage less than the coercive voltage also minimized a breakdown.

Passive Polarization Converter Fabricated by Controlling Optic Axis of Poled Polymer Waveguides (폴링된 폴리머 광도파로의 광축을 조절하여 제작한 수동형 편광 변환기)

  • 오민철;신상영
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.32A no.12
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    • pp.166-172
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    • 1995
  • A novel passive TE/TM polarization mode converter is fabricated by using poled polymer waveguides. The optic axis of the poling induced waveguide is slowly rotated by using a slowly varying structure of poling electrodes. Thus the polarization conversion is achieved as the guided mode propagates through the waveguide. The proposed device is simulated by a full vectorial beam propagation method (VBPM) for anisotropic medium. For the rotation length of 1 mm, the TE polarization of the guided mode is successfully converted to the TM polarization with negligible loss. Based on the simulation results, we fabricated the polarization converter which is tested by using 1.3 $\mu$m laser diode. TE to TM mode conversion is observed with a polarization extinction ratio higher than 30 dB, and the excess loss is less than 1 dB. The polarization conversion is relatively insensitive to wavelength since the device contains no periodic structures. These devices are easier to fabricate than others containing periodic structures.

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Congruent LiNbO3 Crystal Periodically Poled by Applying External Field (외부전계 인가에 의한 조화용융조성 LiNbO3 결정의 주기적 분극반전)

  • Kwon, Soon-Woo;Yang, Woo-Seok;Lee, Hyung-Man;Kim, Woo-Kyung;Lee, Han-Young;Yoon, Dae-Ho;Song, Yo-Seung
    • Journal of the Korean Ceramic Society
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    • v.42 no.11 s.282
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    • pp.749-752
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    • 2005
  • When an electric field higher than a characteristic coercive field is applied to a ferroelectric such as $LiNbO_3$, the orientation of the spontaneous polarization is reversed, which causes the reversal of the sign of odd-rank tensor properties such as electro-optic and nonlinear optic coefficients. A fabrication process of insulator and periodic external field assisted poling of a z-cut $LiNbO_3$ have been optimized for a periodic $180^{\circ}$ phase inversion along z-axis. The poling jig and the poling control system, fully controlled by a computer, for high quality and reproducible PPLN fabrication have been devised. Periodically polarization reversed PPLN was adjusted based on the fabricated thickness of insulator. The poling structure of PPLN was observed under a microscope after etching PPLN samples by an etching solution ($HF:HNO_3$ = 1 : 2) for about 15 min.

Integrated-Optic Polarization Controlling Devices Using Electro-Optic Polymers

  • Oh, Min-Cheol;Hwang, Wol-Yon;Kim, Jang-Joo
    • ETRI Journal
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    • v.18 no.4
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    • pp.287-299
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    • 1997
  • Integrated-optic polarization controlling devices such as polarizers, polarization splitters, and polarization converters, are proposed and demonstrated in nonlinear optic polymers. Poling-induced birefringence in electro-optic polymers is exploited to fabricate the devices. The polymeric waveguide polarizers show low excess losses, and extinction ratios of 20.7 dB and 17.1 dB for TM-pass and TE-pass polarizers, respectively. The polymeric waveguide polarization splitters exhibit TE-TM mode splittings with crosstalk of 14.2 dB and 10.1 dB for TM and TE mode splittings, respectively. The polymeric waveguide polarization converters show successful TE/TM polarization mode conversion with conversion efficiencies of higher than 30 dB. The device employs poling-induced waveguides which have slowly rotating azimuth angle of optic axis along the light propagation direction. The novel polarization converter is insensitive to wavelength and easier to fabricate than the other polarization converters containing periodic structures.

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Periodically domain inversion and optical properties of low-loss Ti : $LiNbO_3$ waveguides (저손실 Ti : $LiNbO_3$ 광도파로의 주기적 분극 반전과 광학특성)

  • Yang, W.S.;Kwon, S.W.;Lee, H.M.;Kim, W.K.;Yoon, D.H.;Lee, H.Y.
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.16 no.2
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    • pp.49-52
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    • 2006
  • Periodic electric field assisted poling low loss (${\sim}0.1dB/cm$) single-mode Ti-diffused waveguides in $LiNbO_3$ has been achieved using a periodically patterned electrode on the +Z surface of Ti : $LiNbO_3$ crystal and homogeneous LiCl solution. Using selective chemical etching, we confirmed the periodic (${\sim}16{\mu}m$) domain inverted structure and measured SH (second harmonic) properties of fabricated periodically poled Ti : $LiNbO_3$ waveguides.

Domain formation and expansion during periodic poling of congruent $LiNbO_3$ using external field (조화용융조성 $LiNbO_3$의 주기적 분극 반전 동안 도메인 생성 및 이동에 관한 연구)

  • Kwon, S.W.;Yang, W.S.;Lee, H.M.;Kim, W.K.;Lee, H.Y.;Yoon, D.H.;Song, Y.S.
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.16 no.2
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    • pp.53-58
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    • 2006
  • When external field was applied to congruent $LiNbO_3$, it was investgated for domain formation and expansion of $LiNbO_3$. The domain wall velocities of 0.5 mm thickness $LiNbO_3$ were 28.70, 16.02 and $5.75{\mu}m/sec$ under poling field of 23.5, 22.0 and 21.0 kV/mm, respectively. As $1 M{\Omega}$ resistor was used in domain inversion system, harmonic domain inversion was not achieved by rapid domain expansion. And 50% duty cycle periodically poled $LiNbO_3$ have been fabricated by charge control using $10 M{\Omega}$ resistor.

Fabrication of a periodically poled MgO : $LiNbO_3$ ridge waveguide for a green laser generation (녹색 광 발진을 위한 주기적 분극 반전된 MgO : $LiNbO_3$ ridge waveguide 제작)

  • Yang, W.S.;Kwon, S.W.;Song, M.K.;Lee, H.M.;Kim, W.K.;Koo, K.H.;Yoon, D.H.;Lee, H.Y.
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.17 no.4
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    • pp.151-155
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    • 2007
  • Quasi-phase-matched (QPM) second harmonic generation (SHG) waveguide devices for a green light generation were fabricated by a periodically patterned electrode on the +Z crystal surface and homogeneous LiCl solution using a 5 mol% MgO doped congruent z-cut lithium niobate crystals. Using selective chemical etching, we confirmed the periodic (${\sim}6.8{\mu}m$) domain inverted structure and measured SHG properties of fabricated periodically poled MgO : $LiNbO_3$ ridge-type waveguides.

Characteristic of $LiNbO_3$ Domain Inversion and Fabrication of Electrooptic Device Application using Domain Reversal ($LiNbO_3$ 기판의 도메인 반전 특성과 이를 이용한 기능성 광변조기의 제작)

  • Jeong, W.J.;Kim, W.K.;Yang, W.S.;Lee, H.M.;Kwon, S.W.;Song, M.K.;Lee, H.Y.
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.44 no.3 s.357
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    • pp.20-25
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    • 2007
  • The periodic domain-inversion in the selective areas of $Ti:LiNbO_3$ Mach-Zender waveguides was performed and band-pass modulators and single sideband (SSB) modulators were fabricated by using domain-reversal. The domain wall velocity was precisely controlled by real-time analysis of a poling-induced response current under an applied voltage. The domain wall velocity was significantly affected by the crystal orientation of the domain wall propagation which influenced the final domain geometry. In a certain case, the decomposition of $LiNbO_3$ crystal was observed, for example, under the condition of too fast domain wall propagation. The fabricated band-pass modulator with a periodic domain-inversion structure showed the maximum modulation efficiency at 30.3 GHz with 5.1 GHz 3dB-bandwidth, and SSB modulator was measured to show 33 dB USB suppression over LSB at 5.8 GHz RF.