Browsing by Author "Teng, Chun-Hao"

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A High-Accuracy Multidomain Legendre Pseudospectral Frequency-Domain Method With Penalty Scheme for Solving Scattering and Coupling Problems of Nano-Cylinders
(2013-03-01)
Wang, Chih-Yu
;
Chung, Shih-Yung
;
Teng, Chun-Hao
;
Wang, Juen-Kai
;
Chen, Chung-Ping
A new multidomain pseudospectral frequency-domain (PSFD) method based on the Legendre polynomials with penalty scheme is developed for numerically modeling electromagnetic wave scattering problems. The primary aim of the proposed method is to more accurately analyzing scattering and coupling problems in plasmonics, in which optical waves interact with nanometer-sized metallic structures. Using light scattering by a silver circular cylinder as a first example, the formulated method is demonstrated to achieve numerical accuracy in near-field calculations on the order of 10(-9) with respect to a unity field strength of the incident wave with excellent exponentially convergent behavior in numerical accuracy. Then, scattering by a dielectric square cylinder and that by several coupled metallic structures involving circular cylinders, square cylinders, or dielectric coated cylinders are examined to provide high-accuracy coupled near-field results.
A Multidomain Pseudospectral Mode Solver for Optical Waveguide Analysis
(2012-07-01)
Chiang, Shun-Fan
;
Lin, Bang-Yan
;
Chang, Hung-Chun
;
Teng, Chun-Hao
;
Wang, Chih-Yu
We propose a pseudospectral mode solver for optical waveguide mode analysis formulated by the frequency-domain Maxwell equations. Special attention is paid upon identifying the required boundary operator for the formulation and the relationships between the derived operator and the physical boundary conditions. These theoretical results are adopted into a Legendre pseudospectral multidomain computational framework to compute the propagation characteristics of optical waveguides. Numerical experiments are conducted, and the expected spectral convergence of the scheme is observed for smooth problems and for problems having field jumps at material interfaces. For dielectric waveguides with sharp corners, the spectral convergence is lost due to the singular nature of fields at the corner. Nevertheless, compared with other methods, the present formulation remains as an efficient approach to obtain waveguide modes.
An error minimized pseudospectral penalty direct Poisson solver
(2012-03-20)
Horng, Tzyy-Leng
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Teng, Chun-Hao
;
應用數學系
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數學建模與科學計算所(含中心)
;
Department of Applied Mathematics
This paper presents a direct Poisson solver based on an error minimized Chebyshev pseudospectral penalty formulation for problems defined on rectangular domains. In this study the penalty parameters are determined analytically such that the discrete L-2 error is minimized. Numerical experiments are conducted and the results show that the penalty scheme computes numerical solutions with better accuracy, compared to the traditional approach with boundary conditions enforced strongly. (C) 2011 Elsevier Inc. All rights reserved.
High-Accuracy Waveguide Leaky-Mode Analysis Using a Multidomain Pseudospectral Frequency-Domain Method Incorporated With Stretched Coordinate PML
(2013-07-15)
Wang, Chih-Yu
;
Liu, Hsuan-Hao
;
Chung, Shih-Yung
;
Teng, Chun-Hao
;
Chen, Chung-Ping
A recently developed pseudospectral frequency-domain (PSFD) method employing a penalty scheme is further incorporated with stretched coordinate perfectly matched layers (PMLs) in order to solve waveguide leaky modes. Several standard leaky-mode slab and circular waveguides, including the W-type and M-type ones, are examined first by solving their complex effective indexes and field profiles, showing that the PSFD method achieves computational accuracy on the order of. Then, this high-accuracy solver is used to analyze waveguide structures with more complicated geometries, such as the leaky six-air-hole fiber, for which self convergence of accuracy in calculated effective indexes is demonstrated to be on the orders of, and two rectilineal waveguides with sharp corners, i.e., the rib waveguide and the photonic wire. Comparison of the PSFD method obtained results for these more complicated waveguide structures with those from other methods in the literature is presented and discussed.
Investigation of Nanoelectromagnetics Problems Using the Multidomain Legendre Pseudospectral Time-Domain Method
(2012)
Chang, Hung-chun
;
Chung, Shih-Yung
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Wang, Chih-Yu
;
Teng, Chun-Hao
;
Wang, Juen-Kai
Nanoelectromagnetics problems in nanophotonics and plasmonics in the optical-wavelength regime are concerned in this paper. Very often such problems demand more accurate electromagnetic computation and analysis. A multidomain Legendre pseudospectral time-domain (PSTD) method recently developed and demonstrated to provide high numerical accuracy is utilized to study light interaction with sub-wavelength three-dimensional plasmonic structures and associated plasmonic resonances. With the multidomain technique, the simulation region is partitioned into curvilinear hexahedral subdomains with better fitting to the structural shapes and material interfaces so as to achieve high-accuracy near-field calculations. Light scattering by multiple plasmonic nanospheres and light transmission through a metallic thin film perforated with periodic apertures are investigated with the PSTD analysis.
Pseudospectral Modeling of Nano-Optics in Ag Sphere Arrays
(2010-10-01)
Lin, Bang-Yan
;
Teng, Chun-Hao
;
Chang, Hung-Chun
;
Hsiao, Hui-Hsin
;
Wang, Juen-Kai
We report a Legendre pseudospectral modeling of silver sphere arrays illuminated by light waves. A special feature of the present computation is that the dispersive nature of silver is described by a Drude-Lorentz model with model parameters obtained by fitting the frequency-domain complex-valued dielectric constants measured experimentally. Numerical validations are conducted based on solving both the near and far fields of the Mie scattering problem, and we observe good convergence on the numerical fields. The far-field patterns of the Ag sphere arrays are simulated. The results are compared to those obtained by the dipole-coupling-model method, and we observe very good agreement between these results. The near-field patterns are also computed, and localized enhanced electric fields in the inter-particle gap regions due to plasmonic coupling between Ag particles are visualized. As the gap between Ag particles is reduced the strength of the localized enhanced electric field is increased.
Pseudospectral Modeling of Nano-Optics in Ag Sphere Arrays
(2010-10-01)
Lin, Bang-Yan
;
Teng, Chun-Hao
;
Chang, Hung-Chun
;
Hsiao, Hui-Hsin
;
Wang, Juen-Kai
We report a Legendre pseudospectral modeling of silver sphere arrays illuminated by light waves. A special feature of the present computation is that the dispersive nature of silver is described by a Drude-Lorentz model with model parameters obtained by fitting the frequency-domain complex-valued dielectric constants measured experimentally. Numerical validations are conducted based on solving both the near and far fields of the Mie scattering problem, and we observe good convergence on the numerical fields. The far-field patterns of the Ag sphere arrays are simulated. The results are compared to those obtained by the dipole-coupling-model method, and we observe very good agreement between these results. The near-field patterns are also computed, and localized enhanced electric fields in the inter-particle gap regions due to plasmonic coupling between Ag particles are visualized. As the gap between Ag particles is reduced the strength of the localized enhanced electric field is increased.
SIMULATING BINARY FLUID-SURFACTANT DYNAMICS BY A PHASE FIELD MODEL
(2012-06-01)
Teng, Chun-Hao
;
Chern, I-Liang
;
Lai, Ming-Chih
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數學建模與科學計算所(含中心)
;
Graduate Program of Mathematical Modeling and Scientific Computing, Department of Applied Mathematics
In this paper, the dynamics of a binary fluid-surfactant system described by a phenomenological phase field model is investigated through analytical and numerical computations. We first consider the case of one-dimensional planar interface and prove the existence of the equilibrium solution. Then we derive the analytical equilibrium solution for the order parameter and the surfactant concentration in a particular case. The results show that the present phase field formulation qualitatively mimics the surfactant adsorption on the binary fluid interfaces. We further study the time-dependent solutions of the system by numerical computations based on the pseudospectral Fourier computational framework. The present numerical results are in a good agreement with the previous theoretical study in the way that the surfactant favors the creation of interfaces and also stabilizes the formation of phase regions.
Simulations of Dielectric and Plasmonic Waveguide-Coupled Ring Resonators Using the Legendre Pseudospectral Time-Domain Method
(2012-06-01)
Chung, Shih-Yung
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Wang, Chih-Yu
;
Teng, Chun-Hao
;
Chen, Chung-Ping
;
Chang, Hung-Chun
The accurate Legendre pseudospectral time-domain (PSTD) method is applied in this paper to the study of optical behaviors of 2-D dielectric and plasmonic waveguide-coupled ring resonators. Based on its inherent multidomain scheme with curvilinear-quadrilateral subdomain partitioning, the PSTD method possesses superior advantage in fulfilling field continuity conditions across material interfaces, which provides better numerical handling upon circular or even more complicated ring structures. Accordingly, investigations of several plasmonic nanoring resonators of different shapes with surface plasmon polariton (SPP) waves propagating on the metal/dielectric/metal waveguides are made with the aids of a well-fitted Drude-Lorentz material-dispersion model through analyzing their characteristics in the near-infrared and visible parts of the light spectrum. Especially, the racetrack-shaped ring is carefully designed with optimized track length to avoid the over-or under-coupling problem between the ring and input waveguides and, thus, achieve excellent spectral performance.
Solving Optical Waveguide Leaky Modes Using a Multidomain Legendre Pseudospectral Frequency-Domain Method
(2013)
Wang, Chih-Yu
;
Chung, Shih-Yung
;
Teng, Chun-Hao
;
Chen, Chung-Ping
;
Chang, Hung-chun
A Legendre pseudospectral frequency-domain (PSFD) method incorporated with stretched coordinate perfectly matched layers (PMLs) and a multidomain technique is established for solving optical waveguide leaky modes. A recently developed penalty scheme is employed to assure numerical accuracy. This high-accuracy solver is used to analyze a leaky six-air-hole microstructured fiber, for which self convergence of accuracy in calculated effective indexes is demonstrated to be on the orders of 10(-14). Then, the photonic wire is analyzed and the comparison with the analysis results from other methods is discussed.