Researcher:
Karabulut, Emine Pınar

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Emine Pınar

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Karabulut

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Karabulut, Emine Pınar

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2008 - 200922010 - 20114

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Researcher Of Publications: search.filters.isAuthorOfPublication.25e06333-cc12-49b2-8edd-0043f0f81401

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    Characterization of finite photonic crystals with defects
    (Institute of Electrical and Electronics Engineers (IEEE), 2011) N/A; Department of Electrical and Electronics Engineering; Karabulut, Emine Pınar; Aksun, M. İrşadi; Reseacher; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; College of Engineering; N/A; 28358
    A simple computational approach is proposed to obtain the dispersion characteristics that could be observed outside of general finite-extent photonic crystals with defects. Since introducing and tailoring defects in photonic crystals are crucial for designing practical devices, the proposed method may play an important role in characterization and optimization of such defects. The method uses reflection data, due to an incident plane wave at a given frequency, collected at the front interface of a photonic crystal. It is simple and applicable for general photonic crystals, that is, photonic crystals with any periodicity, 1D, 2D, and 3D, and even with any kind of defects. The validity of the method was tested and verified on 1D and 2D finite photonic crystals, for which the reflection coefficient data at the front interface can be easily obtained by analytical means and numerical simulations, respectively. In addition, different types of defects, like random and periodic defects, were studied and it has been shown that the method is capable of providing information pertinent to the outside world on the defect modes.
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    Characterization of finite photonic crystals
    (IEEE, 2008) N/A; N/A; Department of Electrical and Electronics Engineering; Karabulut, Emine Pınar; Aksun, M. İrşadi; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 28358
    A new approach is proposed to obtain the dispersion characteristics of finite-extent photonic crystals. The method provides (w - k) diagram and information on the effective constitutive parameters of the structure and is applicable for general photonic crystals, that is, 1D, 2D and 3D photonic crystals with any kind of defects. The method utilizes the reflection data due to an incident plane wave at a given frequency, collected at the front interface of the photonic crystal for different numbers of unit cells. The reflection data can be obtained either analytically or by means of simulations or measurements. The method is verified on 1D and 2D perfect photonic crystals and 1D photonic crystal with defect.
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    Determining the effective constitutive parameters of finite periodic structures: photonic crystals and metamaterials
    (IEEE Computer Society, 2008) Irci, Erdinç; Ertürk, Vakur; Department of Electrical and Electronics Engineering; Aksun, M. İrşadi; Alparslan, Aytaç; Karabulut, Emine Pınar; Faculty Member; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 28358; 231990; N/A
    A novel approach to find the effective electric and magnetic parameters of finite periodic structures is proposed. The method uses the reflection coefficients at the interface between a homogenous half-space and the periodic structure of different thicknesses. The reflection data are then approximated by complex exponentials, from which one can deduce the wavenumber, and the effective electric and magnetic properties of the equivalent structure by a simple comparison to the geometrical series representation of the generalized reflection from a homogenous slab. Since the effective parameters are for the homogenous equivalent of the periodic structure, the results obtained are expected to be independent of the number of unit cells used in the longitudinal direction. Although the proposed method is quite versatile and applicable to any finite periodic structure, photonic crystals and metamaterials with metallic inclusions have been used to demonstrate the application of the method in this paper.
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    Discrete complex image method with spatial error criterion
    (IEEE-Inst Electrical Electronics Engineers Inc, 2011) N/A; N/A; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Karabulut, Emine Pınar; Erdoğan, Alper Tunga; Aksun, M. İrşadi; PhD Student; Faculty Member; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; N/A; 41624; 28358
    Since its first inception, the discrete complex image method (DCIM) has been criticized for the lack of a proper prediction algorithm of the error incurred during the process. Although the method has been improved and modified several times, not being able to input any prior specification or to get any meaningful assessment on the error deters computer-aided design developers and engineers from using it in the development of commercial software and in-house simulation tools. To remedy this short-coming of the otherwise very popular DCIM, a weighted p-norm of the spatial-domain error is defined, and its mapping to the spectral domain is derived and proposed as the metric to be used in the implementation of the DCIM. Once this metric is incorporated into the latest three-level DCIM algorithm, used for the approximation of the spatial-domain Green's functions, it is observed that the weighted error-energy minimization in the spectral domain becomes equivalent to the one in the spatial domain. In addition to introducing an error criterion to the DCIM, the leakage problem, which is inherent to the semi-independent processing of subregions in multilevel implementations of the DCIM, is also addressed and eliminated, resulting in a further improvement of the algorithm and the end result.
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    Discrete complex image method with spatial error criterion and automatic order selection
    (IEEE, 2011) Department of Electrical and Electronics Engineering; N/A; Department of Electrical and Electronics Engineering; Erdoğan, Alper Tunga; Karabulut, Emine Pınar; Aksun, M. İrşadi; Faculty Member; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; Graduate School of Sciences and Engineering; College of Engineering; 41624; N/A; 28358
    Two shortcomings of the otherwise very efficient and hence very popular DCIM approach are remedied in this study. First shortcoming is the lack of an error metric that transforms the spatial-domain error to the spectral domain. In standard DCIM procedures, OLS error minimization in the spectral domain does not correspond to the error minimization in the spatial domain. We propose an error criterion by defining an error metric in the spatial domain and mapping it to the spectral domain. Second, by using the proposed spatial error criterion we propose an automatic order selection procedure to find the number of exponentials that describes the Green's function optimally by employing MDL principle to DCIM. The resulting DCIM algorithm is implemented on three-level DCIM and tested on a typical geometry for validation. © 2011 IEEE.
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    Spatial error criterion for discrete complex image method
    (EUCAP, 2011) Department of Electrical and Electronics Engineering; N/A; Department of Electrical and Electronics Engineering; Erdoğan, Alper Tunga; Karabulut, Emine Pınar; Aksun, M. İrşadi; Faculty Member; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; Graduate School of Sciences and Engineering; College of Engineering; 41624; N/A; 28358
    Although DCIM is very robust and efficient to obtain spatial-domain Green's functions from their spectral-domain counterparts in planar media, the method suffers from the lack of an error metric ensuring the accuracy of the end result, which deters CAD developers and engineers from using it in the development of commercial tools. To remedy this shortcoming of DCIM, a weighted 2-norm of the error in the spatial domain is defined and its mapping to the spectral domain is derived and proposed as the metric to be used in DCIM. In addition, the leakage problem of the multi-level implementations of DCIM is also eliminated. The resulting metric is implemented on the latest three-level DCIM and the proposed three-level DCIM is verified on a typical planar layered geometry. © 2011 EurAAP.