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  • Computational Electromagnetics

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Enhancing the sensitivity of a transmissive graphene-based plasmonic biosensor

Meisam Esfandiari, Saughar Jarchi, Paria Nasiri-Shehni, Mohsen Ghaffari-Miab
Journal PaperApplied Optics , Volume 60 , Issue 5, 2021 February 10, {Pages 1201-1208 }

Abstract

A biosensor platform based on the plasmonic resonance of graphene in the terahertz (THz) range (0.1 to 10 THz) is designed and investigated. The initial design is to create a nanofluidic channel as a sensing layer in the substrate of a biosensor grounded by metal. The sensor consists of a rectangular graphene patch over the substrate, which can be fed by either an external near-field source or an antenna. The presence of molecules in the nanosensing layer causes small changes in the channel’s properties, detectable through the scattering parameters of the designed biosensor. Since biomolecules are poorly absorbed in the initial biosensor, it can be grounded by a graphene sheet that is the same size as the graphene sheet over the substrate

Dyadic Green’s Function of a Cylindrical Isotropic Metasurface

Masoud Hamidi, Hamed Khayam Nekoei, Mohsen Ghaffari-Miab
Conference Paper2021 20th International Conference on Microwave Techniques (COMITE) , 2021 April 19, {Pages 05-Jan }

Abstract

In this paper, dyadic Green’s functions (DGFs) for a point source in the presence of a cylindrical isotropic metasurface with a circular cross-section are presented in closed form. The DGFs are constructed from cylindrical vector wave functions, and scattering coefficients are derived using the method of scattering superposition (SSP). It is assumed that the metasurface is electromagnetically thin. Therefore, the metasurface is suitably modeled using the generalized sheet transition conditions (GSTCs) method. By using the DGFs of this structure, the electric field due to an infinitesimal electric dipole oriented in the direction of cylindrical metasurface in the near- and far-field regions is obtained. Numerical results are compared with

Design of a broadband metamaterial-based acoustic lens using elaborated carpet cloak strategy

S Eslamzadeh, M Ghaffari-Miab, B Abbasi-Arand
Journal Paper , , {Pages }

Abstract

Dyadic Green's function of partially filled graphene‐loaded rectangular waveguides

H Lotfalizadeh, M Ghaffari‐Miab
Journal Paper , , {Pages }

Abstract

Interaction of two guided-mode resonances in an all-dielectric photonic crystal for uniform SERS

Laaya Sabri, Mahmoud Shahabadi, Keyvan Forooraghi, Mohsen Ghaffari-Miab
Journal PaperOptics Express , Volume 28 , Issue 7, 2020 March 30, {Pages 10467-10476 }

Abstract

For sensing and imaging applications of surface-enhanced Raman scattering (SERS), one needs a substrate with the capability of generating a consistent and uniform response and increased signal enhancement. To this goal, we propose a photonic-crystal (PC) structure capable of supporting large field enhancement due to its high quality-factor resonance. Moreover, we demonstrate that the interaction of two modes of this all-dielectric PC can provide an almost uniform field enhancement across the unit cell of the PC. This is of practical importance for SERS applications. The designed structure can support a maximum field enhancement of 70 and 97 percent of uniformity.

Bistable Terahertz Switch designed by Integration of a Graphene Plasmonic Crystal into Fabry-Perot Resonator

Mehdi Dehghan, Mohammad Moravvej-Farshi, Masoud Jabbari, Ghafar Darvish, Mohsen Ghaffari-Miab
Journal PaperIEEE Journal of Selected Topics in Quantum Electronics , 2020 August 14, {Pages }

Abstract

An appropriately designed periodic lattice in graphene can cause plasmonic modes, absorbing a specific THz frequency band, minimizing transmission. A suitable Fabry-Perot cavity, on the other hand, can resonate at another desired frequency in the nearby THz band, enhancing the transmittance. Integrating, these two types of structures into a THz switch, in which the peaks of the plasmonic absorption and the Fabry-Perot resonance band play the role of the OFF and ON states, yielding a bistable switch with a very high output due to the resonance and a high extinction (ON/OFF) ratio. By placing a patterned with an array of circular micro-holes with a plasmonic absorption band centered about 4.1 THz in the middle of a Fabry-Perot vertical cavity

Dyadic Green’s Function for Electric Dipole Excitation of a Perfect Electromagnetic Conductor Sphere

Maryam Hesari-Shermeh, Mehri Ziaee-Bideskan, Mohsen Ghaffari-Miab, Bijan Abbasi-Arand, Keyvan Forooraghi
Journal PaperIEEE Transactions on Antennas and Propagation , 2020 November 18, {Pages }

Abstract

In this paper, we investigate the dyadic Green’s function (DGF) of a perfect electromagnetic conductor sphere (PEMCS) due to electric dipoles, theoretically by employing the scattering superposition principle (SSP) and the Ohm-Rayleigh method. Then the derived DGF is used to calculate the scattered field of a PEMCS due to an arbitrarily oriented infinitesimal electric dipole and also plane wave illumination. Numerical results are compared with those obtained by FEKO commercial software to demonstrate the efficiency and accuracy of the proposed method. The results are in excellent agreement.

OpenACC GPU implementation of double-stage delay-multiply-and-sum algorithm: toward enhanced real-time linear-array photoacoustic tomography

Seyyed Reza Miri Rostami, Moein Mozaffarzadeh, Ali Hariri, Jesse V Jokerst, Mohsen Ghaffari-Miab
Conference PaperPhotons Plus Ultrasound: Imaging and Sensing 2019 , Volume 10878 , 2019 February 27, {Pages 108785C }

Abstract

Double-stage delay-multiply-and-sum (DS-DMAS) is one of the algorithms proposed for photoacoustic image reconstruction where a linear-array transducer is used to detect signals. This algorithm provides a higher contrast image in comparison with the conventional delay-multiply-and-sum (DMAS) and delay-and-sum (DAS), but it imposes a high computational complexity. In this paper, open accelerators (OpenACC) GPU computation parallel approach is used to lessen the computational time and address the high computational time of the DSDMAS for photoacoustic image reconstruction process. Compared with sequential execution of the DS-DMAS on CPU, a speed-up of approximately 74? is achieved (for an image having 1024 ? 1024 pixels). The proposed approach

Channel capacity enhancement by adjustable graphene-based MIMO antenna in THz band

Meisam Esfandiyari, Saughar Jarchi, Mohsen Ghaffari-Miab
Journal PaperOptical and Quantum Electronics , Volume 51 , Issue 5, 2019 May 1, {Pages 137 }

Abstract

This paper offers the design of a graphene-based MIMO antenna with an adjustable radiation pattern for THz communications. To make the radiation pattern adjustable a superstrate layer of graphene based patch, is added to the designed MIMO antenna which increases Channel Capacity. In addition to adjustable radiation pattern, the gain of antenna in the main lobe is also increased. The losses of THz channel is investigated and the angle of the main lobe of the designed antenna is set to the angle with the lowest loss. The channel capacity is evaluated and compared with the antenna without the superstrate layer. It is shown that channel capacity is significantly enhanced.

Ultra-compact Spatial Terahertz Switch Based on Graphene Plasmonic-Coupled Waveguide

Mehdi Dehghan, Mohammad Kazem Moravvej-Farshi, Mohsen Ghaffari-Miab, Masoud Jabbari, Ghafar Darvish
Journal PaperPlasmonics , 2019 January , {Pages 11-Jan }

Abstract

We are proposing graphene (G)-based multilayered plasmonic spatial switch, operating at 10 THz. It is composed of hBN/Ag/hBN/G/hBN/G/hBN/SiO 2/p+-Si multilayers. When a 10-THz transverse magnetic (TM)-polarized signal is normally incident upon the structure top surface, the nanoaperture devised in the Ag nanolayer, acting as a grating, excites surface plasmons at the top graphene micro-ribbons/hBN interface. These surface plasmons depending on the graphenes chemical potentials can be coupled to the lower-right or left graphene micro-ribbons and continue to propagate laterally towards the corresponding output port. Numerical simulations show that a change of∆ V G≈?2.7 V in the voltage, applied to the gated micro-ribbons, can modulate the

Electromagnetic Uncertainty Analysis Using Stochastic FDFD Method

Khadijeh Masumnia-Bisheh, Keyvan Forooraghi, Mohsen Ghaffari-Miab
Journal PaperIEEE Transactions on Antennas and Propagation , 2019 January 31, {Pages }

Abstract

This paper presents a novel stochastic finite difference frequency domain method (S-FDFD) that incorporates the statistical variations of electrical properties directly into the FDFD algorithm by using the delta method approximation. The method is validated through two examples – a 1D bioelectromagnetic layered model and specific absorption rate (SAR) in a 2D slice of a human head model. Comparisons between the single run S-FDFD results and those of the Monte Carlo method (the benchmark in statistical simulations) show that the S-FDFD method can predict the mean and variance of electromagnetic fields with a fair degree of accuracy in a computationally efficient way. Our numerical experiment also shows the accuracy is highly dependent on t

GPU-accelerated Double-Stage Delay-Multiply-and-Sum Algorithm for Fast Photoacoustic Tomography Using LED Excitation and Linear Arrays

Seyyed Reza Miri Rostami, Moein Mozaffarzadeh, Mohsen Ghaffari-Miab, Ali Hariri, Jesse Jokerst
Journal PaperUltrasonic imaging , 2019 July 19, {Pages 0161734619862488 }

Abstract

Double-stage delay-multiply-and-sum (DS-DMAS) is an algorithm proposed for photoacoustic image reconstruction. The DS-DMAS algorithm offers a higher contrast than conventional delay-and-sum and delay-multiply and-sum but at the expense of higher computational complexity. Here, we utilized a compute unified device architecture (CUDA) graphics processing unit (GPU) parallel computation approach to address the high complexity of the DS-DMAS for photoacoustic image reconstruction generated from a commercial light-emitting diode (LED)–based photoacoustic scanner. In comparison with a single-threaded central processing unit (CPU), the GPU approach increased speeds by nearly 140-fold for 1024 ? 1024 pixel image; there was no decrease in accuracy

Multilayer dielectric substrate for improved Raman spectroscopy

Laaya Sabri, Mahmoud Shahabadi, Mohsen Ghaffari-Miab, Keyvan Forooraghi
Journal PaperOptics Communications , 2019 June 27, {Pages }

Abstract

To enhance Raman scattering, we propose a multi-layer substrate which behaves similar to a magnetic mirror or what is also known as high-impedance surface (HIS). Due to this property, the electric field of the illuminating light is increased by a factor of two. This field enhancement doubles the amplitude of the Raman signal generated by the molecules residing on this multi-layer structure. On the other hand, the introduced multi-layer structure is designed to operate as a filter for the scattered field at the Rayleigh wavelength, so that the wave transmitted through this structure mainly contains the Raman signal with 45dB rejection of the Rayleigh wavelength. The designed substrate reduces the complexity of the conventional Raman setup an

Finite Difference Generated Transient Potentials of Open-Layered Media by Parallel Computing Using OpenMP, MPI, OpenACC, and CUDA

Seyyed Reza Miri Rostami, Mohsen Ghaffari-Miab
Journal PaperIEEE Transactions on Antennas and Propagation , 2019 January , {Pages }

Abstract

The implementation of time-domain Green’s func-tions (TDGFs) in graphics processing unit (GPU) and central processing unit (CPU) using finite-difference scheme is shown. The TDGFs represent the transient electric scalar and magnetic vector potentials due to a horizontal electric dipole (HED) in open-layered media. The layered media is bounded with Perfectly Matched Layer (PML), Symmetry Axis and Perfect Electric Conductor (PEC). We adopted four different parallel approaches as follows: 1) OpenMP (Open Multiprocessing) CPU implementation; 2) MPI (Message Passing Interface) CPU implementation; 3) OpenACC (Open Accelerators) GPU implementation; and 4) CUDA (Compute Unified Device Architecture) GPU implementation. The accuracy and efficiency

GPU-accelerated Double-Stage Delay-Multiply-and-Sum Algorithm for Fast Photoacoustic Tomography Using LED Excitation and Linear Arrays

Seyyed Reza Miri Rostami, Moein Mozaffarzadeh, Mohsen Ghaffari-Miab, Ali Hariri, Jesse Jokerst
Journal PaperUltrasonic imaging , Volume 41 , Issue 5, 2019 September , {Pages 301-316 }

Abstract

Double-stage delay-multiply-and-sum (DS-DMAS) is an algorithm proposed for photoacoustic image reconstruction. The DS-DMAS algorithm offers a higher contrast than conventional delay-and-sum and delay-multiply and-sum but at the expense of higher computational complexity. Here, we utilized a compute unified device architecture (CUDA) graphics processing unit (GPU) parallel computation approach to address the high complexity of the DS-DMAS for photoacoustic image reconstruction generated from a commercial light-emitting diode (LED)–based photoacoustic scanner. In comparison with a single-threaded central processing unit (CPU), the GPU approach increased speeds by nearly 140-fold for 1024 ? 1024 pixel image; there was no decrease in accuracy

Geometrically Stochastic FDTD Method for Uncertainty Quantification of EM Fields and SAR in Biological Tissues

Khadijeh Masumnia-Bisheh, Keyvan Forooraghi, Mohsen Ghaffari-Miab, Cynthia Furse
Journal PaperIEEE Transactions on Antennas and Propagation , 2019 July 26, {Pages }

Abstract

This paper presents a stochastic scheme called geometrically stochastic FDTD (GS-FDTD) to insert the statistical variation of model geometry directly into the finite difference time domain (FDTD) method. Both 1D and 2D GS-FDTD formulations are presented. The method is utilized to investigate the impact of tissue size variation on the calculated EM fields in 1D and 2D layered and cylindrical biological models. In addition, we assess the SAR variance in a 2D slice of a human head model at 835 MHz with the size of the outer layer consisting of skin, ear and nose varying ?10 percent. Also an improved method of calculating specific absorption rate (SAR) variance is presented. Results are verified using the Monte Carlo technique.

Ultra-Compact Bidirectional Terahertz Switch Based on Resonance in Graphene Ring and Plate

Masoud Jabbari, Mehdi Dehghan, Ghafar Darvish, Mohsen Ghaffari-miab
Journal PaperJournal of Optoelectronical Nanostructures , Volume 4 , Issue 4, 2019 December 1, {Pages 99-112 }

Abstract

Revised 23 Jul. 2019; Accepted 11 Aug. 2019; Published 15 Sep. 2019) Abstract: In this paper, we present a switch based on coupling and resonance in the graphene plate and rings operating at 10 THz. This structure consists of several layers of Hexagonal Boron Nitride (hBN), SiO2 and P+Si, such that graphene plates and rings are inside the hBN layer. The terahertz wave is incident from the upper part of the switch and Surface Plasmons (SPs) are excited by the grating in the structure on the graphene plate beneath the nano-aperture and moves towards the ports available on the left and right of the switch. At first, at the certain applied voltage, the SPs cross the left port and this port is ON. With the increase in voltage and the change in t

Stochastic Finite Difference Frequency Domain Method

Khadijeh Masumnia-Bisheh, Keyvan Forooraghi, Mohsen Ghaffari-Miab
Conference Paper2018 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting , 2018 July 8, {Pages 2315-2316 }

Abstract

This paper presents a novel stochastic numerical method called stochastic finite difference frequency domain (S-FDFD). S-FDFD introduced in this paper directly inserts the statistical variations of electrical properties into the FDFD. Comparison between full-fledged multi run Monte Carlo results and those of single run S-FDFD shows that the S-FDFD method can predict the mean and variance of EM fields with a fair degree of accuracy in a computationally efficient way.

Dyadic Green’s Function of a Conical Cavity With Impedance Spherical Cap

Khadijeh Masumnia-Bisheh, Mohsen Ghaffari-Miab, Keyvan Forooraghi
Journal PaperIEEE Transactions on Antennas and Propagation , Volume 66 , Issue 11, 2018 November , {Pages 6015-6022 }

Abstract

This paper presents the dyadic Green’s function (DGF) of a conical cavity with impedance spherical cap, which is derived using the eigenfunction expansion method and the method of scattering superposition. The -field inside the conical cavity from an arbitrarily oriented infinitesimal dipole and a dipole antenna is obtained numerically by making use of the developed DGF. Then, the DGF results are compared with those obtained by CST microwave studio commercial software, which is in a good agreement. The effect of surface impedance value on the -field is also investigated.

Cross-Layer Energy Efficient Resource Allocation in PD-NOMA based H-CRANs: Implementation via GPU

Ali Mokdad, Paeiz Azmi, Nader Mokari, Mohammad Moltafet, Mohsen Ghaffari-Miab
Journal PaperarXiv preprint arXiv:1803.07772 , 2018 March 21, {Pages }

Abstract

In this paper, we propose a cross layer energy efficient resource allocation and remote radio head (RRH) selection algorithm for heterogeneous traffic in power domain-non-orthogonal multiple access (PD-NOMA) based heterogeneous cloud radio access networks (H-CRANs). The main aim is to maximize the EE of the elastic users subject to the average delay constraint of the streaming users and the constraints, RRH selection, subcarrier, transmit power and successive interference cancellation. The considered optimization problem is non-convex, NP-hard and intractable. To solve this problem, we transform the fractional objective function into a subtractive form. Then, we utilize successive convex approximation approach. Moreover, in order to increas

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