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time-domain 2D modeling of slab-waveguide-based photonic-crystal devices in the presence of radiation losses

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS 2002年第5期34卷 387-393页

作者： Qiu, M Jaskorzynska, B Swillo, M Benisty, H Royal Inst Technol KTH Dept Microelect & Informat Technol Lab Photon & Microwave Engn S-16440 Kista Sweden Ecole Polytech Phys Mat Condensee Lab F-91128 Palaiseau France

Devices based on two-dimensional (2D) photonic crystals (PCs) arc typically realized as 3D structures consisting of an array of holes (or rods) vertically etched through a slab waveguide. The existence of holes in a slob waveguide may induce strong radiation losses to the slab claddings. Exact modeling of devices affected by such losses requires 3D calculations. In the present Letter, with the use of the effective-index method to account for the vertical confinement and the effective losses method by the nonvanishing conductivity, the 3D modeling is reduced into 2D. It is then shown that good agreement with experiments can be obtained for slab-waveguide-based photonic crystal devices. (C) 2002 Wiley Periodicals, Inc.

关键词： finite-difference time-domain method radiation losses photonic crystals photonic crystal waveguides

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Single-mode silicon optical switch with T-shaped SiO₂ optical waveguide as a control gate

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JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 2002年第4B期41卷 2563-2565页

作者： Kobayashi, H Iida, Y Omura, Y Kansai Univ Fac Engn High Technol Res Ctr Suita Osaka 5648680 Japan

An electrooptic silicon switch and modulator are reported. A single-mode silicon optical switch with a T-shaped SiO2 optical waveguide as a control gate is studied by electromagnetic field simulation using the finite-difference time-domain method. It has been shown that signal light of lambda = 1.55 mum is attenuated by more than 30 dB under the illumination of control light of lambda = 0.85 mum. For a structure with an interaction length of 1 mum, it is estimated that the control light power of about 5.5 mW is needed. For a new structure with a long interaction length, the control light power is estimated to be about 44 muW when 50% of the transferred energy is consumed in the silicon core, the interaction area is 10 mum long, and the lifetime of carriers is 10 mus.

关键词： silicon microphotonics silicon on insulator optical switch optical modulator free carrier effect finite-difference time-domain method

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Microstrip filter design using FDTD and neural networks

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MICROWAVE AND OPTICAL TECHNOLOGY LETTERS 2002年第3期34卷 219-224页

作者： Banciu, MG Ambikairajah, E Ramer, R Univ New S Wales Sch Elect Engn & Telecommun Sydney NSW 2052 Australia

A new design technique using the FDTD method and neural networks is applied to a microstrip filter. The total design time is reduced by two means. First, an iterative ARMA signal estimation technique is utilized to reduce the computation time for each FDTD run. Second, the number of FDTD simulations is decreased with the use of the device model provided by a neural network with the ARMA coefficients at the output. The trained network was then incorporated to an optimization procedure for a microstrip filter design. (C) 2002 Wiley Periodicals, Inc.

关键词： microstrip filters microwave design neural networks finite-difference time-domain method

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Optical waveguide analysis using a Yee-lattice-based modified finite-difference formula for an arbitrary dielectric interface

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ELECTRONICS AND COMMUNICATIONS IN JAPAN PART II-ELECTRONICS 2002年第12期85卷 1-9页

作者： Ando, T Nakayama, H Yamauchi, J Nakano, H Hosei Univ Fac Engn Koganei Tokyo 1848584 Japan

A modified finite-difference formula including the boundary condition of the field is applied to the eigenmode and propagation analysis of optical waveguides. First, in order to show the effectiveness of the modified finite-difference formula, the eigenmode solver is formulated using the imaginary axis method based on the Yee lattice. The fundamental mode of a two-dimensional step-index slab is computed. It is proved that the discontinuous field at the dielectric interface can be evaluated accurately. Further, a circular fiber is analyzed and its converged field is obtained with a lattice spacing larger than that in the conventional method. Finally, by using the finite-difference time-domain method, the propagating wave in a slanted waveguide is analyzed. It is pointed out that the quantization error caused by the staircase approximation can be reduced by the application of the modified finite-difference formula. (C) 2002 Wiley Periodicals, Inc.

关键词： Yee lattice modified finite-difference formula imaginary axis method finite-difference time-domain method eigenmode analysis propagating wave analysis quantization error

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Light propagation through alignment-patterned liquid crystal gratings

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MOLECULAR CRYSTALS AND LIQUID CRYSTALS 2002年 375卷 491-500页

作者： Scharf, T Bohley, C Univ Neuchatel Inst Microtechnol CH-2000 Neuchatel Switzerland

We analysed the light propagation through alignment-patterned liquid crystal films where the alignment is planar and homeotropic for different domains, respectively. Using elastic theory the nematic director field can be analytically calculated with the method of conformal mapping in the one elastic constant approximation. A smooth change of the nematic director field is found with defect points at the substrate surfaces. In order to investigate the propagation of light passing through such a liquid crystalline thin film with spatially varying birefringence, we use a rigorous method. The use of rigorous methods allows the simulation of the time-dependent electric and magnetic fields for a region that is two-dimensional and possibly anisotropic. Simulations are made by the finite-difference time-domain method (FDTD), which is a numerical approach for the rigorous solution of the Maxwell equations. This method, in contrast to methods of geometrical and matrix optics, delivers results which include diffraction and scattering.

关键词： liquid crystal gratings anisotropic gradient index media light propagation finite-difference time-domain method

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Simulation of simultaneous tracking/data signal detection using novel aperture-mounted surface recording head

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JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 2002年第3B期41卷 1628-1631页

作者： Tanaka, K Ohkubo, T Oumi, M Mitsuoka, Y Nakajima, K Hosaka, H Itao, K Univ Tokyo Grad Sch Frontier Sci Bunkyo Ku Tokyo 1138656 Japan Seiko Instruments Inc Matsudo Chiba 2702222 Japan

Recently, near-field surface recording based on near-field optical principles has been vigorously studied for higher data storage density. In near-field optics which utilizes an aperture, in addition to the high spatial resolution property, there is another characteristic that the shape of the optical spot can be arbitrarily controlled by the aperture configuration, and its application to various technologies in the optical disk drive is possible. From this perspective, we propose a novel tracking method utilizing an asymmetric configured aperture head which could provide continuous signal of readout data and tracking error simultaneously, and analyze its data read-out and tracking detection performance through the three-dimensional finite-difference time-domain (3D-FDTD) method. Our simulations reveal that this novel tracking head has sufficient data readout performance and high tracking sensitivity, and has the potential to readout both a data signal and a tracking signal simultaneously.

关键词： near-field optics near-field optical head tracking method finite-difference time-domain method

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Mechanisms for enhancing power throughput from planar nano-apertures for near-field optical data storage

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JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 2002年第3B期41卷 1632-1635页

作者： Shi, XL Hesselink, L Stanford Univ Dept Elect Engn Palo Alto CA 94305 USA

Near-field optical data storage systems are important for ultrahigh density data storage. One type of near-field optical data Storage system uses a planar nano-aperture to define the data storage resolution. However, conventional nano-apertures have a tradeoff between resolution and power throughput. Recently, we reported a novel "C"-aperture design to overcome this problem. In this paper, we present our study on the mechanisms for power throughput enhancement, based on a detailed study of nano-slits using numerical simulations. We find that generating a propagation mode is essential for high power throughput, and by optimizing the design of the aperture thickness, resonant transmission can be achieved for even higher power throughput.

关键词： nano-aperture nano-slits near-field optics finite-difference time-domain method power throughput "C"-aperture mechanism

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Analysis of resonance processes in microstrip ring resonators by the FDTD method

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MICROWAVE AND OPTICAL TECHNOLOGY LETTERS 2001年第5期28卷 312-321页

作者： Semouchkina, E Cao, WW Mittra, R Yu, WH Penn State Univ Mat Res Lab University Pk PA 16802 USA Penn State Univ Dept Math University Pk PA 16802 USA Penn State Univ Dept Elect Engn University Pk PA 16802 USA

In this paper, the finite-difference time-domain method is used to analyze resonance processes in microstrip ring resonators, which are either edge or side coupled to the feedlines, in both the time and frequency domains. Standing waves established in resonant structures are visualized by simulating the spatial distribution of electromagnetic fields at resonant frequencies. The wave processes, which determine the resonance formation in edge- and side-coupled resonators, are found to be significantly different in these two structures. (C) 2001 John Wiley & Sons, Inc.

关键词： microwave resonator microstrip ring finite-difference time-domain method electromagnetic waves resonance

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FDTD and PSTD simulations for plasma applications

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IEEE TRANSACTIONS ON PLASMA SCIENCE 2001年第2期29卷 341-348页

作者： Fan, GX Liu, QH Hutchinson, SA Duke Univ Dept Elect & Comp Engn Durham NC 27708 USA Sandia Natl Labs Albuquerque NM 87185 USA

Three-dimensional finite-difference time-domain (FDTD) and pseudospectral time-domain (PSTD) algorithms, with perfectly matched layer absorbing boundary condition, are presented for nonmagnetized plasma as a special case of general inhomogeneous, dispersive, conductive media. The algorithms are tested for three typical frequency bands, and an excellent agreement between the FDTD/PSTD numerical results and analytical solutions is obtained for all cases. Several applications, such as laser-pulse propagation in plasma hollow channels, surface-wave propagation along a plasma column of finite length, and energy deposition of electron cyclotron resonance plasma source, demonstrate the capability and effectiveness of these algorithms. The PSTD algorithm is more efficient and accurate than the FDTD algorithm, and is suitable for large-scale problems, while the FDTD algorithm is more suitable for fine details. The numerical results also show that plasma has complex transient responses, especially in the low-frequency and resonance regimes, Because of their flexibility and generality, the algorithms and computer programs can be used to simulate various electromagnetic waves-plasma interactions with complex geometry and medium properties, both in time and frequency domains.

关键词： finite-difference time-domain method perfectly matched layer plasma plasma applications plasma sources pseudospectral time-domain method

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finite-difference time-domain analysis on nonlinear Fabry-Perot resonator in optical waveguide geometry

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JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS 2001年第4A期40卷 2259-2263页

作者： Fujii, M Okamoto, T Haraguchi, M Fukui, M Al-Bader, SJ Univ Tokushima Fac Engn Dept Opt Sci & Technol Tokushima 7708506 Japan King Fahd Univ Petr & Minerals Dept Elect Engn Dhahran 31261 Saudi Arabia

The finite-difference time-domain (FDTD) method is applied to investigate the characteristics of nonlinear Fabry-Perot (FP) resonators in optical waveguide geometries. Our treatment, which is the extension of Tran's method developed to analyse the characteristics of nonlinear photonic crystals, correctly reproduces analytical results on optical bistabilities of the FP resonator provided by Chen and Mills in 1987. It is found that the minimum power required for optical bistabilities is significantry decreased by adopting the optical waveguide geometry, compared with the case of Chen and Mills, i.e., a conventional nonlinear FP interferometer.

关键词： finite-difference time-domain method nonlinear Fabry-Perot resonator third-order nonlinear optical effect guided optics

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