• Title/Summary/Keyword: Longitudinal Modal Transmission-Line Theory

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Ultracompact Polarization-Insensitive Directional Coupler based on Double Sandwiched Rib-Type Waveguide (이중 샌드위치 Rib-형 도파로에 기초한 초소형 편광 무의존성 방향성 결합기)

  • Ho, Kwang-Chun
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.14 no.3
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    • pp.171-176
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    • 2014
  • The polarization characteristics of ultracompact polarization-insensitive directional coupler (PIDC) based on double sandwiched rib-type waveguide are explored in detail by using longitudinal modal transmission-line theory (L-MTLT). To obtain the polarization-insensitive condition of ultracompact directional coupler, the coupling length and coupling efficiency as functions of the refractive index and thickness of sandwiched rib-type waveguide are analyzed for quasi-TE and quasi-TM modes. The numerical results show that the ultracompact polarization-insensitive coupler with hundreds of micrometer scales is realized by properly choosing structural and material parameters of double sandwiched layers. Furthermore, the influence of fundamental mode profile, which is distributed in lateral waveguide of coupler, on the coupler performance has been investigated.

Nano-scale Power Splitters by using Plasmonic Multimode Interference Couplers (플라즈마 다중모드 간섭 결합기를 사용한 나노 크기의 전력분배기)

  • Ho, Kwang-Chun
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.11 no.4
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    • pp.47-52
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    • 2011
  • Nano-scale power splitter based on Si plasmonic waveguides are designed by utilizing the multimode interference (MMI) coupler. Effective dielectric method and longitudinal modal transmission-line theory are used for simulating the light propagation and optimizing the structural parameters at 3-D guiding geometry. The designed $1{\times}2$ 50:50 MMI power splitter has a nano-scale size of only $800nm{\times}850nm$. In order to achieve a variable power splitting ratio, a $2{\times}2$ MMI coupler is designed and the corresponding power splitting ratio can be tuned in the range of 78.5%:15.5%~5.5%:86.6%. Also, it is shown that it has a large bandwidth of $1.5{\mu}m{\sim}1.7{\mu}m$. In this range, the transmission is over 0.8.

Design of Polarization-Insensitive Directional Couplers and Multimode Interference Couplers Integrated with Bragg Grating Waveguide (Bragg 격자구조가 집적된 편광 무의존성 방향성 결합기와 다중모드 간섭 결합기의 설계)

  • Ho, Kwang-Chun
    • Korean Journal of Optics and Photonics
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    • v.18 no.5
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    • pp.295-302
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    • 2007
  • This paper presents a rigorous comparison of the design characteristics of polarization-insensitive directional coupler (DC) and multimode interference (MMI) coupler based on rib type waveguides, by using longitudinal modal transmission-line theory (L-MTLT). It shows that the multimode mixing and interference property of MMI can be structurally designed through the continuous evolution of the two-mode coupling property of DC. It also compares and analyzes the coupling efficiency along with the coupling length and the wavelength between polarization-insensitive DC and MMI. From the design properties obtained, it demonstrates for the first time the integration of polarization-insensitive DC or MMI with a Bragg grating and evaluates precisely the filtering characteristics. The numerical results reveal that the DC, as long as it is designed to have the same coupling length for TE and TM modes, has better performance than the MMI in polarization-insensitive filtering behaviour. However, it shows that the MMI with much less coupling length than DC is preferred in the miniaturization of integrated devices.

Implementation of Polarization-Insensitive Directional Coupler using Curved Waveguides (곡면형 도파로를 사용한 편광 무의존성 방향성 결합기의 구현)

  • Ho, Kwang-Chun
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.16 no.1
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    • pp.239-244
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    • 2016
  • The polarization characteristics of polarization-insensitive directional coupler based on double sandwiched rib-type and curved waveguides are explored in detail by using conformal transformation method (CTM) and longitudinal modal transmission-line theory(L-MTLT). To obtain the polarization-insensitive condition of polarization-insensitive curved directional coupler(PI-CDC), the coupling length and coupling efficiency according to the inner radius of PI-CDC are analyzed for quasi-TE and quasi-TM modes. The numerical results show that the PI-CDC with a few micrometer scales can be realized by properly choosing the curvature and structural and material parameters of double sandwiched layers. Furthermore, the mode profiles propagating through PI-CDC are evaluated, and the influence on coupler performance has been investigated.

Realization of Plasmonic Adaptive Coupler using Curved Multimode Interference Waveguide (곡면형 다중모드 간섭 도파로를 사용한 플라즈마 적응 결합기의 구현)

  • Ho, Kwang-Chun
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.16 no.2
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    • pp.165-170
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    • 2016
  • Nano-scale power splitter based on curved plasmonic waveguides are designed by utilizing the multimode interference (MMI) coupler. To analyze easily the adaptive properties of plasmonic curverd multimode interference coupler(PC-MMIC), the curved form transforms equivalently into a planar form by using conformal transformation method. Also, effective dielectric method and longitudinal modal transmission-line theory are used for simulating the light propagation and optimizing the structural parameters at 3-D guiding geometry. The designed $2{\times}2$ PC-MMIC does not work well for quasi-TM mode case due to the bending structure, and it does not exist 3dB coupling property, in which the power splitting ratio is 50%:50%, for quasi-TE mode case. Further, the coupling efficiency is better when the signal is incident at channel with large curvature radius than small curvature radius.