Yuhei Ishizaka

Yuhei Ishizaka
Kanto Gakuin University · College of Science and Engineering

PhD

About

26
Publications
2,123
Reads
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531
Citations
Additional affiliations
April 2014 - March 2015
Hokkaido University
Position
  • PostDoc Position

Publications

Publications (26)
Article
We present a photonic-plasmonic mode converter using modecoupling-based polarization rotation for connecting a silicon wire and hybrid plasmonic waveguides on a metal-inserted silicon platform. By using the polarization rotator based on defect-introduced silicon wire waveguide, the proposed mode converter can convert the photonic TE mode into the h...
Article
A metal-assisted silicon slot waveguide for highly sensitive gas detection is proposed. To show the superiority of the proposed structure, the optical confinement factor in the gas region and the sensitivity are theoretically investigated using the two-dimensional vector finite element method. Numerical results show that the proposed structure can...
Article
A 3-D finite-element time-domain beam propagation method is described for the first time, to the best of our knowledge, for the analysis of transmission characteristics of any kind of photonic structures. In order to avoid nonphysical reflections from computational window edges, the perfectly matched layer boundary condition is introduced. Furtherm...
Conference Paper
We demonstrated a six-spatial-mode multiplexer using effective index matching and adiabatic mode transition. Six-mode multiplexing including the equal effective indices of LP 21 b and LP 02 was successfully achieved with a fabricated PLC on one chip.
Article
A rigorous definition of nonlinear parameter ? for high-index-contrast (HIC) periodic optical waveguides, such as photonic crystal (PC) optical waveguides, is proposed. The definition is fully vectorial, and approximations assumed in previous works are unnecessary. The ? values calculated by the proposed definition are compared with those obtained...
Article
A 3-D finite-element mode-solver, based on a self-consistent algorithm, is newly developed for nonlinear periodic optical waveguides. The developed method makes it possible to calculate various nonlinear characteristics based on optical Kerr effect rigorously, including the nonlinear phase shift, the nonlinear refractive index distribution, and γ-v...
Article
A PLC-based LP11 mode rotator is proposed. The proposed mode rotator is composed of a waveguide with a trench that provides asymmetry of the waveguide. Numerical simulations show that converting LP11a (LP11b) mode to LP11b (LP11a) mode can be achieved with high conversion efficiency (more than 90%) and little polarization dependence over a wide wav...
Article
Full-text available
An ultrabroadband silicon wire polarization beam combiner/splitter (PBCS) based on a wavelength-insensitive coupler is proposed. The proposed PBCS consists of three identical directional couplers and two identical delay lines. We design the PBCS using the 3-D finite element method. Numerical simulations show that the proposed PBCS can achieve the t...
Conference Paper
PLC-type LP11 mode rotator with a single-trench waveguide is designed and fabricated. Converting LP11a (LP11b) mode into LP11b (LP11a) mode is achieved with high conversion efficiency over a wide wavelength range.
Conference Paper
We propose coupled resonator optical waveguides based on slotted nanobeam cavities. We show that our proposed structure can achieve a high effective nonlinear coefficient because of small group velocity and light confinement in slot region.
Article
Full-text available
We present transmission-efficient bent and crossing silicon slot waveguides for compact silicon slot waveguide-based circuits. To begin with, using the 3-D vector finite-element method, we investigate the transmission characteristics of a bent silicon slot waveguide with an asymmetric slot that is connected to straight waveguides. Numerical results...
Conference Paper
We propose a novel surface plasmon nanocavity composed of a metallic wall and a 1-D photonic crystal. Numerical results show that the proposed structure achieves a ultra-small mode volume of 0.065(λ /n)3.
Article
We propose the coupled ring resonator based on one-dimensional photonic crystal (1-D PC) nanocavity. The proposed structure is composed by introducing 1-D PC nanocavity into the CROW based on ring resonator, and we expect that it can achieve small group velocity. We investigate the transmission characteristics of the proposed structure by using 2-D...
Conference Paper
We propose coupled resonator optical waveguides based on slotted nanobeam cavities. Numerical results show that our proposed structure can achieve a high effective nonlinear coefficient because of small group velocity and small effective mode area.
Conference Paper
We propose a metallic wall-based plasmon nanocavity with 1-D photonic crystals. Numerical results show that the proposed structure achieves a mode volume of 0.39(λ/n)3 and a Q factor of 604.
Conference Paper
We propose a hybrid plasmonic waveguide with a uniform silica layer and evaluate its propagation length and coupling characteristics. Numerical results show that we should carefully choose structural parameters to obtain a longer propagation length.
Conference Paper
We investigate structural dependence of nonlinear characteristics in slot waveguides composed of photonic crystal nanobeam cavities. Numerical results show that our proposed structure can realize a high effective nonlinear coefficient.
Article
Full-text available
We investigate slow-light-enhanced nonlinear characteristics in slot waveguides composed of photonic crystal (PC) nanobeam cavities. To evaluate the effective nonlinear coefficient, numerical simulations are performed by using 3-D vector finite-element method for periodic waveguide analysis. Results show that the maximum nonlinear coefficient of 11...
Article
A three-dimensional vectorial finite element method (3-D-VFEM) for waveguide discontinuity problems is newly formulated and implemented. Through the use of the 3-D-VFEM, transmission characteristics of two types of crossing slot-waveguides with finite core-height are investigated for the first time. One is a direct crossing and the other is a cross...
Article
A compact two-mode (de)multiplexer (TM-MUX) based on Si nanowire for mode-division multiplexing is designed. The TM-MUX is composed of two multimode interference (MMI) waveguides and a butterfly-shape tapered phase shifter between two MMI waveguides. Numerical simulations show that the designed device is compact compared with conventional-mode (de)...
Conference Paper
We investigate transmission characteristics of two types of crossing slot-waveguides using three-dimensional finite element method, a direct crossing and a crossing with filled slots. Results show that three-dimensional analysis considering the finite core-height is indispensable.
Article
We present a novel design method and potential application for optical XOR, XNOR, NAND, and OR logic gates for binary-phase-shift-keyed signal processing devices. The devices are composed of multi-mode interference waveguides and convert the phase information of the input signal to amplitude at the output. We apply the finite element method for num...
Article
We propose a novel ultra-compact all-optical XOR and AND logic gates without using nonlinear optics. In order to realize these devices, we adopt photonic crystal waveguides (PCWs) based on multi-mode interference devices. Numerical results show that the operating bandwidth of the ON to OFF logic-level contrast ratio of not less than 6.79dB is 35nm...
Article
We propose architecture of reconfigurable optical logic gates for BPSK signal. The logic gates operate as NAND, OR, XOR, and XNOR by changing phase of input-lights appropriately and produce high contrast ratio.
Article
We propose ultra-compact all-optical XOR and AND logic gates based on multi-mode interference (MMI) without using nonlinear optics. Numerical simulations show that the least ON to OFF logic-level contrast ratio is 13.3 dB for XOR logic gate and 4.3 dB for AND logic gate in the whole C-band.

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