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Engineering educational research section Information and Communication Technology Program |
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Associate Professor |
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NAKA Yoshihiro
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Papers 【 display / non-display 】
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NAKA Yoshihiro, NISHIMOTO Masahiko, YOKOTA Mitsuhiro
IEICE Transactions on Electronics E108.C ( 4 ) 195 - 200 2025.4
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：一般社団法人 電子情報通信学会
An optical resonator with two waveguide discontinuities constructed by a metal-dielectric-metal plasmonic waveguide has been analyzed using the finite-difference time-domain (FD-TD) method with the piecewise linear recursive convolution (PLRC) method. The waveguide discontinuity has been expressed as an equivalent transmission line circuit whose circuit parameters are estimated from the reflection coefficients analyzed by the FD-TD method. We have confirmed the validity of the circuit configuration because the reflection characteristics of the equivalent circuit with the circuit parameters agree with those of the FD-TD method. Next, we have analyzed a resonator structure with two waveguide discontinuities and shown that the equivalent circuit gives a good approximation for the structure with a large difference in waveguide width at the discontinuities, in which conventional equivalent circuits had large errors.
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YOKOTA Mitsuhiro, NAKA Yoshihiro
Lecture Notes in Electrical Engineering 1322 LNEE 291 - 300 2025.2
Publishing type：Research paper (international conference proceedings) Publisher：Lecture Notes in Electrical Engineering
The resonance properties of two-dimensional ring resonators consisted of the slot waveguide structure with throughput and drop ports and ring waveguides are numerically analyzed using the FDTD method. Polarization deals with TM waves that have components crossing the slot region. In the case of two-dimensional structures, the eigenmodes of slot waveguides can be analytically obtained, and these obtained eigenmodes are used as incident waves in the FDTD method. In numerical calculations, the influence of the radius of the ring waveguide, and the refractive index of the background medium on the resonant characteristics are investigated. Furthermore, sensitivity and FoM (figure of merit), which are important evaluation indices when using the ring resonator as a refractive index sensor, are also discussed.
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Numerical Examination on Resonance Properties of Ring Resonatore Consisted of Slot Waveguide Reviewed
YOKOTA Mitsuhiro, NAKA Yoshihiro
J107-C ( 7 ) 267 - 273 2024.7
Language：Japanese Publishing type：Research paper (scientific journal)
The resonance characteristics of a two-dimensional ring slot waveguide resonator consisting an input/output waveguide and a ring waveguide are numerically investigated using the FDTD method and the obtained results are discussed from the perspective of coupled-mode theory. Polarization deals with TM waves whose electric field has a component that crosses the slot region. In the case of a two-dimensional structure, the eigenmodes of the slot waveguide can be obtained analytically, and the eigenmodes as the incident wave in the FDTD method are applied. In the numerical calculations, the effects of the radius of the ring waveguide, the distance between the input/output waveguide and ring waveguide, and the refractive index of the background medium on the resonance characteristics are investigated. Also, the sensitivity and figure of merit (FoM), which are important evaluation indicators when using a ring resonator as a refractive index sensor are examined.
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NAKA Yoshihiro, NISHIMOTO Masahiko, YOKOTA Mitsuhiro
IEICE Transactions on Electronics E107.C ( 5 ) 141 - 145 2024.5
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：The Institute of Electronics, Information and Communication Engineers
An efficient optical power splitter constructed by a metal-dielectric-metal plasmonic waveguide with a resonator structure has been analyzed. The method of solution is the finite difference time domain (FD-TD) method with the piecewise linear recursive convolution (PLRC) method. The resonator structure consists of input/output waveguides and a narrow waveguide with a T-junction. The power splitter with the resonator structure is expressed by an equivalent transmission-line circuit. We can find that the transmittance and reflectance calculated by the FD-TD method and the equivalent circuit are matched when the difference in width between the input/output waveguides and the narrow waveguide is small. It is also shown that the transmission wavelength can be adjusted by changing the narrow waveguide lengths that satisfy the impedance matching condition in the equivalent circuit.
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Equivalent Circuit Expression of Optical Resonator Structure Constructed by Two-Dimensional MDM Plasmonic Narrow Waveguide Reviewed
NAKA Yoshihiro, NISHIMOTO Masahiko, YOKOTA Mitsuhiro
J106-C ( 9 ) 360 - 365 2023.9
Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)
The resonator structure constructed by a metal-dielectric-metal plasmonic waveguide have been expressed by an equivalent transmission line circuit. The resonator structure consists of input/output waveguides and a narrow waveguide. We have found that the transmittance of the equivalent circuit agreed with that by the finite difference time domain (FD-TD) method with the piecewise linear recursive convolution (PLRC) method when the difference in width between the input/output waveguides and the narrow waveguide is small. The result also shown that high transmittance was achieved by increasing waveguide widths of input/output and narrow waveguide.
Books 【 display / non-display 】
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Electromagnetic Theory and Applications for Photonic Crystals
K.Yasumoto(Eds.), H.Ikuno, Y.Naka, et al.（ Role： Joint author）
CRC Press 2005.10
Total pages：464 Responsible for pages：401-444 Language：English Book type：Scholarly book
Presentations 【 display / non-display 】
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2次元MDMプラズモニック導波路により構成される共振器構造を有する曲がり導波路の特性解析
中良弘, 横田光広, 西本昌彦
2021年電子情報通信学会ソサイエティ大会 2021.9.17
Event date： 2021.9.14 - 2021.9.17
Language：Japanese Presentation type：Oral presentation (general)