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Optical Circuits Made of Spoof Plasmonic Structures with Wide-Band Transmission Resonance and the Impact of Fano Resonance
, M.Sc. Thesis Sharif University of Technology ; Mehrany, Khashayar (Supervisor)
Abstract
Due to the growing need for plasmonic wavs in microwave and terahertz spectra, a periodic arrangement of one-dimensional cut-through slits is investigated and an equivalent model based on the effective medium theory is derived. In contrast to the all previous attempts that were successful in mimicking only the zeroth-order diffracted waves, the proposed effective medium is capable of mimicking all diffraction orders. The parameters of the equivalent model are established by comparing the scattered waves of the semi-homogeneous medium and those of the main structure obtained by invoking the rigorous mode matching approach based on the single mode approximation inside the slits. This medium is...
Fourier modal method formulation for fast analysis of two-dimensional periodic arrays of graphene
, Article Journal of the Optical Society of America B: Optical Physics ; Vol. 31, issue. 5 , 2014 , pp. 987-993 ; ISSN: 07403224 ; Khavasi, A ; Akbari, M ; Sharif University of Technology
Abstract
Recently, an approximate boundary condition [Opt. Lett. 38, 3009 (2013)] was proposed for fast analysis of onedimensional periodic arrays of graphene ribbons by using the Fourier modal method (FMM). Correct factorization rules are applicable to this approximate boundary condition where graphene is modeled as surface conductivity. We extend this approach to obtain the optical properties of two-dimensional periodic arrays of graphene. In this work, optical absorption of graphene squares in a checkerboard pattern and graphene nanodisks in a hexagonal lattice are calculated by the proposed formalism. The achieved results are compared with the conventional FMM, in which graphene is modeled as a...
Creation of artificial surface conductivity on metallic metamaterials
, Article Journal of Lightwave Technology ; Volume 30, Issue 12 , February , 2012 , Pages 1789-1794 ; 07338724 (ISSN) ; Khavasi, A ; Rezaei, M ; Mehrany, K ; Sharif University of Technology
2012
Abstract
Metal films with a periodic arrangement of cut-through slits are studied to show that artificial surface conductivity is created at the flat interface between the periodic slits and the cover/substrate. The presence of surface conductivity when the periodic structure is modeled by an effective refractive index can describe how non-specular higher diffracted orders affect the specular zeroth diffracted order. The magnitude of this surface conductivity is controlled geometrically. The artificial surface conductivity is pure imaginary and thus reactive if all non-specular orders are evanescent. This is usually the case in the low frequency regime. At higher working frequencies when some...
Physics of broadband Brewster transmission through square array of rectangular metallic pillars
, Article Journal of the Optical Society of America B: Optical Physics ; Volume 32, Issue 6 , 2015 , Pages 1202-1207 ; 07403224 (ISSN) ; Khavasi, A ; Mehrany, K ; Sharif University of Technology
OSA - The Optical Society
2015
Abstract
The physics behind the broadband Brewster transmission through square arrays made of rectangular metallic pillars is explored by appealing to the effective medium theory. First, an analytical solution is given for the principal electromagnetic mode propagating between the pillars, and then, the mode matching technique is invoked to extract the parameters of the effective medium model. In this fashion, the pillars are homogenized via a diagonal anisotropic tensor and the effects of higher diffracted orders are included in the effective medium theory by attributing a surface conductivity to the surface boundary of the array. It is shown that the former effectuates the wideband Brewster effect...
Circuit model for plasmons on graphene with one-dimensional conductivity profile
, Article IEEE Photonics Technology Letters ; Volume 28, Issue 3 , 2016 , Pages 355-358 ; 10411135 (ISSN) ; AbdollahRamezani, S ; Arik, K ; Rejae, B ; Khavasi, A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
Abstract
The scattering of graphene surface plasmons normally incident on a line discontinuity in graphene surface conductivity is investigated. The effect of the length of the transition region on the reflection and transmission coefficients is studied. It is shown that the reflection coefficient is reduced by widening the transition region. Based on the results obtained, a transmission line model is derived for the graphene sheet in which the discontinuity is represented by a simple circuit. This model is next used to design graphene-based bandpass and bandstop filters with arbitrary bandwidth in the terahertz regime
Modeling of periodic array of cut-through slits with sinusoidal surface conductivity at the interfaces of an anisotropic medium
, Article IEEE Transactions on Antennas and Propagation ; Volume 66, Issue 10 , 2018 , Pages 5630-5633 ; 0018926X (ISSN) ; Mehrany, K ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2018
Abstract
A periodic arrangement of 1-D slits carved in a perfect electric conductor is investigated, and an equivalent model which features sinusoidal surface conductivity on its upper and lower interfaces is derived. Therefore, and in sheer contrast to all the previous attempts that were successful in mimicking only the zeroth-order diffracted waves, it is capable of emulating both specular and nonspecular diffraction orders. The accuracy of the model is verified by the full-wave simulations. The proposed model is used to study the sharp Fano-type extraordinary transmission resonances arising in the structure. The transmission spectrum near these resonances is derived in terms of Fano resonance...
Greatly reduced radiation loss in planar waveguides with two-dimensional conducting interfaces
, Article IET Optoelectronics ; Volume 2, Issue 4 , 2008 , Pages 158-164 ; 17518768 (ISSN) ; Zareian, N ; Mehrany, K ; Sharif University of Technology
2008
Abstract
A new strategy for radiation loss reduction in curved slab waveguides is presented. The proposed strategy is based on the proper modification of the boundary conditions at the core-to-cladding interface, whereupon extremely thin conductive nanolayers with non-zero surface conductance are imposed. The obtained numerical results show a noticeable decrease in the overall loss level. © 2008 The Institution of Engineering and Technology
Surface electromagnetic waves supported by nano conducting layers with inhomogeneities in the conductivity profile
, Article Optical and Quantum Electronics ; Volume 40, Issue 1 , 2008 , Pages 23-40 ; 03068919 (ISSN) ; Mehrany, K ; Sharif University of Technology
2008
Abstract
Conducting interfaces and nano conducting layers can support surface electromagnetic waves. Uniform charge layers of non-zero thickness and their asymptotic behavior toward conducting interfaces of infinitely small thicknesses, where the thin charge layer is modeled via a surface conductivity σ s , are already studied. Here, the possible effects of inhomogeneity in the conductivity profile of the thin conducting layers are investigated for the first time and a new approximate yet accurate enough analytical formulation for mode extraction in such structures is given. In order to rigorously analyze the structure and justify the proposed approximate formulation, the Galerkin's method with...
Electromagnetic behaviour of nano plasmonic layer
, Article Photonics North 2006, Quebec City, QB, 5 June 2006 through 8 June 2006 ; Volume 6343 II , 2006 ; 0277786X (ISSN) ; 0819464287 (ISBN); 9780819464286 (ISBN) ; Rashidian, B ; Chamanzar, M ; Sharif University of Technology
2006
Abstract
Recently, interaction of electromagnetic waves with conducting interfaces has been studied and several applications have been proposed. For instance, new type of photonic crystals similar to Kronig-Penny electronic crystals has been implemented by using these structures. In these structures a free two dimensional interface charge layer is generated at the dielectric interfaces and interesting phenomena are observed. In this manuscript, the effect of finite charge layer thickness and its asymptotic behavior toward conducting interface, where the thin charge layer is modelled via a surface conductivity σs, is numerically studied for the first time. Two different regimes are considered: first,...
A simple label-free electrochemical DNA biosensor based on carbon nanotube-DNA interaction
, Article RSC Advances ; Volume 6, Issue 19 , 2016 , Pages 15592-15598 ; 20462069 (ISSN) ; Salimian, R ; Kalhor, H. R ; Sharif University of Technology
Royal Society of Chemistry
2016
Abstract
A simple platform based on a hairpin oligonucleotide switch and multi-walled carbon nanotubes (MWCNTs) for the ultrasensitive detection of specific DNA sequences has been developed. In this approach, the π-stacking interaction of single-strand DNA-MWCNT was employed to construct an electrochemical DNA biosensor. Changes to the surface conductivity, based on the MWCNT replacement, were monitored by using the electrochemical species [Fe(CN)6]3-/4- as a redox probe. Morphological and voltammetric characterizations of the electrode surface were performed using atomic force microscopy (AFM), energy dispersive spectroscopy (EDS), cyclic voltammetry (CV), differential pulse voltammetry (DPV) and...
Forbidden spatial frequencies in periodic structures composed of subwavelength nano conducting layers
, Article 2006 International Conference on Nanoscience and Nanotechnology, ICONN 2006, Brisbane, 3 July 2006 through 6 July 2006 ; 2006 , Pages 474-477 ; 1424404533 (ISBN); 9781424404537 (ISBN) ; Rashidian, B ; Sharif University of Technology
2006
Abstract
Recently, electromagnetic slow wave propagation in Kronig-Penny photonic crystals composed of conducting interfaces constituted of extremely thin charge layers has been studied, where analytic expressions for Bloch wave numbers in terms of normalized frequency were derived, asymptotic behavior of electromagnetic slow wave propagation in these structures was investigated at different regimes, and the possibility of observing forbidden spatial frequencies was numerically demonstrated. In this manuscript, the existence and electromagnetic behavior of such waves together with the possibility of having forbidden spatial frequency are investigated by taking the finiteness of charge layer thickness...
Coupled surface electromagnetic waves supported by subwavelength nano conducting layers
, Article 2006 International Conference on Nanoscience and Nanotechnology, ICONN 2006, Brisbane, 3 July 2006 through 6 July 2006 ; 2006 , Pages 501-504 ; 1424404533 (ISBN); 9781424404537 (ISBN) ; Rashidian, B ; Sharif University of Technology
2006
Abstract
Recently, a group of novel devices based on conducting interfaces has been proposed. These conducting interfaces can be implemented by using the inversion layer of MOS structures, trapped charges or depletion layer charges. It has been shown that these structures can support surface electromagnetic waves. In this paper, the coupling of surface electromagnetic waves supported by nano charge layers is analyzed and its asymptotic behavior toward conducting interfaces, where the thin charge layer of finite thickness is modeled via a surface conductivity σs, is numerically studied for the first time. The numerical results driven by coupled mode theory approach are justified by solving exact...