Papers by Sakineh Monfared
Optical and Quantum Electronics
The present study experimentally and theoretically demonstrated an all-optical switch based on a ... more The present study experimentally and theoretically demonstrated an all-optical switch based on a two-dimensional plasmonic crystal structure which was covered by a graphene layer. The optical modes in the photonic band gap of the crystal can be tuned due to the surface plasmon resonance of plasmonic crystal and nonlinear Kerr effect of graphene. Therefore, in the present study, the plasmon resonance wavelength was shifted about 10 and 2.1 nm for the transverse electric and the magnetic polarization in 58° incident angle, respectively. To get switching manner, by applying the 1550 nm infrared laser as a pump the electric field was increased due to large Kerr nonlinearity of graphene,n 2 ≈ 10 −7 cm 2 /W. As a result, refractive index was changed and thus the resonance wavelength of surface plasmon was shifted. In order to confirm the experimental results, Kerr nonlinear effect of graphene, and optical electric field distribution at resonance wavelength have been simulated. Based on the results, this switch had three main advantages such as small size, high tunablitiy, and easier fabrication compared to the other methods, which use defect photonic crystal structures.
Multiple signal classification (MUSIC) is a popular subspace direction of arrival (DOA) estimatio... more Multiple signal classification (MUSIC) is a popular subspace direction of arrival (DOA) estimation algorithm with high resolution and relatively low computational complexity. In order to DOA estimation of wideband cyclostationary communication signals, modified cyclic MUSIC algorithms are proposed. Three well-known algorithms which are investigated in this research are average cyclic MUSIC (ACM), extended wideband cyclic MUSIC (EWCM) and generalized wideband cyclic MUSIC (GWCM). Moreover, uniform linear array (ULA) is not able to estimate and separate signal sources located at angles close to the array endfire, therefore, three ULA-based geometries are considered to improve the DOA estimation of wideband cyclostationary signals. In this paper, ACM, EWCM and GWCM algorithms, considering four type of arrays, ULA, Shirvani-Akbari array (SAA), L-shaped and V-shaped geometries are investigated. Based on spatial spectrum and angular root mean square error (RMSE) of ACM, EWCM and GWCM algo...
In addition to a brief review on narrowband direction of arrival (DOA)estimation, the main purpos... more In addition to a brief review on narrowband direction of arrival (DOA)estimation, the main purpose of this article is to evaluate and compare the performance of narrowband DOA estimation methods. This paper presents the performance analysis of eight DOA estimation algorithms in three categories, minimum variance distortionless response (MVDR) and delay&sum of classical category, multiple signal classification (MUSIC), Root-MUSIC, estimation of signal parameters via rotational invariance technique (ESPRIT), and minimum norm of subspace-based category, and also deterministic maximum likelihood (DML) and stochastic maximum likelihood (SML) belong to ML category. We present the description and compare the performance, angular accuracy and resolution, of these algorithms for a uniform linear array(ULA),based on three metrics, the root mean square error (RMSE), normalized root mean square error (NRMSE) and the number of detected signal sources. Three cases, single, double and five source ...
Electro-optical switch based on one-dimensional graphene-plasmonic crystals
Optical Materials, 2021
In the present study, an electro-optical switch using one-dimensional plasmonic photonic crystals... more In the present study, an electro-optical switch using one-dimensional plasmonic photonic crystals and bilayer graphene was demonstrated experimentally and theoretically. The optical modes of band gap in crystal can be tuned due to the unique optical properties of plasmonic surface resonance at grating and graphene layers. In addition, the excitation of the periodic arrays of metallic resulted in exciting plasmonic surface lattice resonance and creating two reflectance modes for magnetic polarization at 54° incidence angle. Further, the chemical potential of graphene was controlled by applying a gate voltage to achieve an optoelectronic switching operation. Applying voltage of 1 V led to a sharp increase in the relative permittivity of bilayer graphene around the first resonance. Thus, the light was absorbed, its intensity deceased, and the plasmonic resonance wavelength shifted by a value of ~9 nm. Based on the results, using this new kind of structures had advantages such as small ...
Two-dimensional plasmonic multilayer as an efficient tool for low power random lasing applications
Waves in Random and Complex Media
In addition to a brief review on narrowband direction of arrival (DOA)estimation, the main purpos... more In addition to a brief review on narrowband direction of arrival (DOA)estimation, the main purpose of this article is to evaluate and compare the performance of narrowband DOA estimation methods. This paper presents the performance analysis of eight DOA estimation algorithms in three categories, minimum variance distortionless response (MVDR) and delay & sum of classical category, multiple signal classification (MUSIC), Root-MUSIC, estimation of signal parameters via rotational invariance technique (ESPRIT), and minimum norm of subspace-based category, and also deterministic maximum likelihood (DML) and stochastic maximum likelihood (SML) belong to ML category. We present the description and compare the performance, angular accuracy and resolution, of these algorithms for a uniform linear array (ULA), based on three metrics, the root mean square error (RMSE), normalized root mean square error (NRMSE) and the number of detected signal sources. Three cases, single, double and five sou...
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Papers by Sakineh Monfared