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ABSTRACT: In this paper, a 3 × 1 Multiplexer/Demultiplexer (MUX/DEMUX) Photonic Crystal (PhC) based structure is presented. This is
achieved by carefully considering the coupling length of the propagating wave and accurately engineering the geometrical design
of the microcavities. The design is highly selective, such that, a microcavity embedded between two waveguides selects a particular
wavelength to couple from one waveguide into an adjacent waveguide. The numerical technique used for the designs throughout
this paper is the Complex Envelope Alternating Direction Implicit Finite Difference Time Domain (CE-ADI-FDTD).
KeywordsPhotonic crystal–Waveguide–Multiplexer–Complex-envelope alternating-direction-implicit finite-difference-time-domain (CE-ADI-FDTD)
Optical and Quantum Electronics 04/2012; 42(8):425-433. · 0.82 Impact Factor
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ABSTRACT: In this paper, several nonlinear media with different instantaneous third-order nonlinearity responses are analysed. A Finite-Difference-Time-Domain
method (FDTD), developed for nonlinear structures, is used to analyse the nonlinear waveguides and periodic nonlinear structures
that exhibit attractive properties that make them suitable for novel devices with wavelength tuneable characteristics.
Optical and Quantum Electronics 04/2012; 38(15):1217-1235. · 0.82 Impact Factor
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ABSTRACT: In this paper an accurate analysis of two-dimensional (2D) Photonic Crystal (PhC) based multimode resonant cavities is carried
out. The analysis is performed with a robust and accurate Finite Volume Time Domain (FVTD) technique. The analysis proves
the ability of the FVTD method to extract different resonant modes from a multimode PhC resonant cavity with the use of appropriate
source profiles. A detailed explanation on how the source is engineered and used to excite different modes is given. Furthermore,
parameters such as resonant frequency and quality factor for each resonant mode are accurately calculated.
Optical and Quantum Electronics 04/2012; 40(11):875-890. · 0.82 Impact Factor
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ABSTRACT: In this letter, highly nonlinear birefringent soft glass photonic crystal fiber is presented and analyzed using the full vectorial finite-difference method. The suggested design has a central hole infiltrated with a nematic liquid crystal (NLC). The reported design offers high birefringence of 0.042 at the operating wavelength 1.55 μm with low losses for the two polarized modes. In addition, high nonlinearities of 425.5 W<sup>-1</sup> km<sup>-1</sup> and 470.8 W<sup>-1</sup> km<sup>-1</sup> are achieved for the quasi-transverse electric (TE) and quasi-transverse magnetic (TM) modes, respectively, at the operating wavelength of 1.55 μm.
IEEE Photonics Technology Letters 11/2011; · 2.19 Impact Factor
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ABSTRACT: This study presents an accurate numerical analysis of a microcavity ring resonator based on high-index-contrast waveguide. The analysis is carried out using a multiresolution time domain (MRTD) scheme that provides high numerical precision without the strict limitation on the space discretisation as compared to the commonly used finite-difference time domain (FDTD). By relying on higher-order approximation of discretisation in space, the proposed MRTD approach outperforms the FDTD method and is thus a more suitable candidate for large-scale simulations. The uniaxial perfectly matched layer is carefully applied to truncate the computational domain. The analysed parameters are the coupling coefficients between the input/output waveguides and the ring, the resonance frequencies and the free spectral range. The effect of the structure geometry parameters such as the gap between the ring and input/output waveguides, the ring radius and the width of the input/output waveguide and the ring resonator is thoroughly investigated. The numerical results reveal that the suggested MRTD allows using about twice the spatial step size required by FDTD yet providing same level of accuracy.
IET Optoelectronics 09/2011; · 1.03 Impact Factor
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ABSTRACT: In this paper, an improved design of photonic crystal (PhC)-based multiplexer/demultiplexer (MUXDEMUX) devices is presented. This is achieved using careful geometrical design of microcavities with respect to the coupling length of the propagating wave. The nature of the design means that a microcavity embedded between two waveguides selects a particular wavelength to couple from one waveguide into the adjacent waveguide showing high selectivity. The numerical technique used for the designs throughout this article is the complex envelope alternating direction implicit finite difference time domain (CE-ADI-FDTD). Also, improvements have been made on the performance of the perfectly matched layers (PML) by presenting an accurate physical model of discretisation error.
IET Optoelectronics 09/2010; · 1.03 Impact Factor
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ABSTRACT: Different configurations of a T-junction power splitter are investigated using complex-envelope alternating-direction-implicit finite-difference time-domain method. The use of reflectors on both sides of the waveguide significantly improved the performance of the T-junction waveguide after optimising the gradient of the reflectors. Cavity resonators have been added to the structure, and the transmission power on both sides of the T-junction structure is maximised. Furthermore, a photonic crystal (PhC)-based T-junction has been investigated. The results show that the use of the PhC has a major impact on the performance of T-junction.
IET Optoelectronics 05/2009; · 1.03 Impact Factor
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ABSTRACT: An accurate analysis of nonlinear photonic crystal (PhC) based resonant cavities is carried out. The nonlinearity considered for this analysis is a third-order nonlinearity with media composed of Kerr-like dielectric materials with an instantaneous nonlinearity. The analysis is performed with a robust and accurate finite-volume time-domain (FVTD) technique that for the first time has been extended in order to simulate nonlinear material with a Kerr-like instantaneous nonlinearity. From the analysis, interesting properties are revealed from the exploit of nonlinear characteristics of the PhC-based resonant cavities, properties that can be usefully applied for the realisation of all-optical circuits and specifically for optical switches.
IET Optoelectronics 01/2009; · 1.03 Impact Factor
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ABSTRACT: A multiresolution time-domain (MRTD) technique is proposed and applied to the analysis of arbitrarily shaped photonic devices. The suggested method implements the multiresolution analysis in the context of method-of-moments for the solution of Maxwell's equations. To improve the capabilities of the proposed method, the uniaxial perfectly matched layers absorber for the MRTD is rigorously incorporated and better performance is reported over the conventional finite-difference time-domain. Various numerical examples demonstrate the stability and numerical precision of the suggested MRTD method for both linear and nonlinear applications. Moreover, the application of the suggested MRTD scheme for the design of a photonic crystal-based optical wavelength filter and for the analysis of a frequency converter is presented.
IET Optoelectronics 01/2009; · 1.03 Impact Factor
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ABSTRACT: A rigorous, full-vectorial and computationally efficient finite-element-based modal solution, together with junction analysis and beam propagation approaches have been used to study bending loss, transition loss, mode coupling, and polarization coupling in bent optical waveguides. The waveguide offset and their widths have been optimized to reduce the transition loss and the mode beating.
Applied Optics 07/2008; 47(16):2961-70. · 1.41 Impact Factor
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ABSTRACT: In this letter, a new explicit time-domain method for the analysis of light propagation in photonic bandgap (PBG) devices is suggested. In essence, this method is based on the finite volume that employs triangular elements in order to accurately represent curved boundaries encountered in PBG devices. Moreover, uniaxial perfectly matched layer absorbing boundary conditions has also been incorporated to rigorously truncate the computational domain. The high numerical precision of the suggested approach is demonstrated through numerical examples.
IEEE Photonics Technology Letters 04/2008; · 2.19 Impact Factor
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ABSTRACT: In this paper a T-junction power splitter by using different structure is investigated using the finite time difference domain method (FDTD). The variation of the width of one arm of T-junction has a significant impact on the transmitted, radiated and reflected power on both sides. The variation of the cavity parameters on one side of the T-junction lead to a dramatic changes of the ratio of power distribution in the waveguides. Furthermore, the variations of the gradient of the reflectors for symmetric and asymmetric T-junction resonators have shown a great effect on the transmission properties.
Computational Electromagnetics in Time-Domain, 2007. CEM-TD 2007. Workshop on; 11/2007
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ABSTRACT: In this paper, a Multiresolution Time-Domain (MRTD) approach that relies on expanding the fields in terms of Cohen-Daubechies-Feaveau (CDF) biorthogonal-wavelet class is presented to analyze optical guided-wave devices. The results prove the computational efficiency of the method over the traditional Finite Difference Time Domain (FDTD).
Computational Electromagnetics in Time-Domain, 2007. CEM-TD 2007. Workshop on; 11/2007
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ABSTRACT: In this paper, a new alternating direction implicit finite difference time domain (ADI-FDTD) method has been presented. The method relies on a more stable formulation of the perfectly matched layer (PML) absorbing boundary condition making it suitable for the simulation of photonic crystals (PhCs) based devices. Its accuracy and efficiency are demonstrated by numerical examples which are shown to be in excellent agreement with those reported in literature.
Computational Electromagnetics in Time-Domain, 2007. CEM-TD 2007. Workshop on; 11/2007
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ABSTRACT: In this paper an accurate finite element time domain analysis of electromagnetic wave propagation in Electromagnetic Acoustics Transducer (EMAT) is presented. The suggested approach considers the solution "complete" source current density. This model is shown to give more accurate results. A detailed investigation has been performed varying model parameters such as lift off and coil dimension.
Computational Electromagnetics in Time-Domain, 2007. CEM-TD 2007. Workshop on; 11/2007
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ABSTRACT: In this paper, an improved complex-envelope alternating-direction-implicit finite-difference time-domain (CE-ADI-FDTD) method has been presented for the analysis of photonic-bandgap cavities. The improvement relies on a different approach of the perfectly matched-layer absorbing-boundary condition in order to avoid the formation of instability, as reported in the literature. The high numerical precision and efficiency obtained are clearly demonstrated through the agreement of the results obtained using CE-ADI-FDTD and their counterparts obtained using other rigorous approaches reported in the literature
Journal of Lightwave Technology 02/2007; 25(1):440-447. · 2.78 Impact Factor
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S.S.A. Obayya
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ABSTRACT: A numerically efficient scalar analysis of optical-fiber-facet problems based on the finite-element scheme is presented. By adopting the Taylor's series expansion of the characteristic matrix at the discontinuity plane, an accurate and yet numerically efficient approach is suggested for calculating the reflected and transmitted fields at discontinuities with circular symmetry. The scattering of the scalar LP<sub>01</sub> mode and higher order LP<sub>0m</sub> modes at both uncoated and coated optical-fiber facets has been analyzed, and the accuracy of the present finite-element approach is revealed through the excellent agreement of its results with those in the literature.
Journal of Lightwave Technology 06/2006; · 2.78 Impact Factor
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ABSTRACT: Experimental results are presented to demonstrate polarization conversion in passive deep-etched gallium arsenide waveguides. The effect due to process-dependent features of waveguide cross-section geometry, in particular the asymmetry resulting from nonvertical etching, is investigated. A qualitative agreement with vector finite element method (VFEM) simulations is shown. A coupled-mode formulation is used to describe the behavior. The results are compared with an elliptical-polarization analysis, obtained from measurements of the polarization angles of the fundamental waveguide modes and the difference between their effective indices. A novel technique used to carry out effective-index-difference measurements is reported.
Journal of Lightwave Technology 04/2006; 24(3):1425- 1432. · 2.78 Impact Factor
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ABSTRACT: The imaginary distance full vectorial finite element based beam propagation method (IDVFEBPM) is applied to perform an accurate modal solution to photonic crystal fibres (PCFs). The robust perfectly matched layer (PML) boundary condition is employed at the edges of the computational window in order to account for the leakage property of the modes. The effects of the number of holes and the geometrical parameters of the PCF on the effective index, the confinement losses, the effective mode area and the dispersion of the fundamental mode have been thoroughly studied.
IEE Proceedings - Optoelectronics 11/2005; · 0.71 Impact Factor
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ABSTRACT: The evolution of the optical beam profile along a high-power tapered semiconductor amplifier has been demonstrated by using rigorous and full-vectorial numerical approaches, based on the finite-element method. Numerically simulated results indicate the generation of many higher order modes, and their interference with the fundamental mode causes a variation of the optical beam, both along the transverse and the axial directions, which could significantly modify the output beam quality.
Journal of Lightwave Technology 07/2005; 23(6):2124- 2130. · 2.78 Impact Factor
