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Arash Sabatyan

Bio: Arash Sabatyan is an academic researcher from Urmia University. The author has contributed to research in topics: Zone plate & Optical vortex. The author has an hindex of 14, co-authored 70 publications receiving 471 citations.


Papers
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Journal ArticleDOI
TL;DR: A type of Fresnel zone plate in which its phase is shifted radially outward can easily and precisely turn an incident plane wave into an annular beam at its focal plane and the width of the annulus is a function of focal length.
Abstract: We introduce a type of Fresnel zone plate (FZP) in which its phase is shifted radially outward. This FZP can easily and precisely turn an incident plane wave into an annular beam at its focal plane. High efficiency and flexibility are the advantages of generating doughnut beams by this method. By performing direct calculations and using Bessel function properties, it is shown that a radially shifted zone plate produces annulus focus. Furthermore, by simulating the modified phase structure, in addition to demonstrating the formation of a ring-shaped focus, we also showed that its radius merely depends on the amount of the shift. We also showed that the width of the annulus is a function of focal length. Simulation results were thoroughly examined by experiments. Finally, it is clearly revealed that at a certain distance from the focal plane along the beam propagation, an annular beam is transformed into a Bessel beam, and a focal line is formed.

46 citations

Journal ArticleDOI
01 Nov 2013-Optik
TL;DR: In this article, the amplitude of diffracted plane wave at the focal plane of photon sieves with different focal lengths is calculated via convolving operation but has advantageous of taking very very short time.

30 citations

Journal ArticleDOI
TL;DR: In this article, two models of spiral zone plate-based diffractive elements are presented to generate petal-like and optical ring lattice beams, which are named azimuthal phase-shifted zone plates.
Abstract: We aim here to present two models of spiral zone plate-based diffractive elements. To this end, it is shown that by a given combination of two spiral zone plates (SZPs) with opposite-signed charge strengths some novel elements are born whose phase structures are azimuthally shifted. Therefore, they are named azimuthal phase-shifted zone plates. Generally speaking, it is illustrated that both of the two models have the same diffractive functions in generating a variety of petal-like and optical ring lattice beams. Regarding the topological charge of the superimposed SZPs denoted by P1 and P2, it is also elaborated that when the modulus of |P1|−|P2| is of unity, the former beam is generated, while the values greater than unity cause the latter one to be generated. Additionally, the number of petals or lattices is simply manageable and given by |P1|+|P2|. Furthermore, defocusing surveys manifest preserving the shape of the beams in a rather long focal depth and partial rotation of them around the propagation axis is also evident. Numerical results are verified by experiments.

30 citations

Journal ArticleDOI
TL;DR: It is demonstrated that, for an MRSSZP with topological charge 2, an array of dark cores is formed, which have phase structures similar to that of the interference of optical vortices with opposite topological charges.
Abstract: Herein, we present a so-called multiregion spiral square zone plate (MRSSZP), in which a spiral square zone plate is divided into a few regions, so that every region is composed of Fresnel zones, and the first zone of a given region is the same as the last zone of the previous region from a transmission point of view. We show that an MRSSZP can generate unique features of an array of an optical vortex with topological charge ±1, so that the number of vortices is directly related to the number of regions. We also demonstrate that, for an MRSSZP with topological charge 2, an array of dark cores is formed, which have phase structures similar to that of the interference of optical vortices with opposite topological charges. Besides, the focused vortex array follows a modulo-4 transmutation rule. In addition, when the topological charge becomes multiples of 4, an array of focal bright spots surrounded by a dark ring is generated. Numerical and experimental results verify the superior features of an MRSSZP.

28 citations

Journal ArticleDOI
TL;DR: In this article, the surface plasmon resonance (SPR)-based biosensing is an accurate and sensitive technique used to evaluate the biomolecular interactions in real time in a label-free environment.
Abstract: Surface plasmon resonance (SPR)-based biosensing is an accurate and sensitive technique used to evaluate the biomolecular interactions in real time in a label-free environment. Several new approaches have been proposed to improve the sensitivity of SPR sensors. The development of sensing surfaces can significantly improve the performance of biosensors; graphene and graphene oxide (GO) offer several advantages due to their extraordinary optical and structural properties. In this paper, the SPR biosensor structure based on graphene and GO linking layers are suggested. For proposed configurations, the features and characteristics such as reflectivity and sensitivity using the finite element analysis (FEA) model are discussed and compared with results from N-layer model. The effect of cap layer thickness in the sensitivity of the SPR biosensor has been calculated. Computational results show that the proposed graphene and GO-based SPR biosensor have more than two and four times greater sensitivity than the conventional gold film-based SPR sensor respectively due to their better adsorption of biomolecules.

28 citations


Cited by
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01 Mar 2011
TL;DR: In this paper, high magnetic field scanning tunneling microscopy and Landau level spectroscopy of twisted graphene layers grown by chemical vapor deposition was performed. But the results were limited to the case of twisted bilayer bilayer graphene.
Abstract: We report high magnetic field scanning tunneling microscopy and Landau level spectroscopy of twisted graphene layers grown by chemical vapor deposition. For twist angles exceeding ~3° the low energy carriers exhibit Landau level spectra characteristic of massless Dirac fermions. Above 20° the layers effectively decouple and the electronic properties are indistinguishable from those in single-layer graphene, while for smaller angles we observe a slowdown of the carrier velocity which is strongly angle dependent. At the smallest angles the spectra are dominated by twist-induced van Hove singularities and the Dirac fermions eventually become localized. An unexpected electron-hole asymmetry is observed which is substantially larger than the asymmetry in either single or untwisted bilayer graphene.

353 citations

Journal ArticleDOI
TL;DR: In this article, an ultrathin epitaxial graphite graphite (NPEG) was grown by thermal decomposition on the (0001) surface of 6H-SiC and characterized by surface-science techniques.
Abstract: We have produced ultrathin epitaxial graphite films which show remarkable 2D electron gas (2DEG) behavior. The films, composed of typically 3 graphene sheets, were grown by thermal decomposition on the (0001) surface of 6H-SiC, and characterized by surface-science techniques. The low-temperature conductance spans a range of localization regimes according to the structural state (square resistance 1.5 kOhm to 225 kOhm at 4 K, with positive magnetoconductance). Low resistance samples show characteristics of weak-localization in two dimensions, from which we estimate elastic and inelastic mean free paths. At low field, the Hall resistance is linear up to 4.5 T, which is well-explained by n-type carriers of density 10^{12} cm^{-2} per graphene sheet. The most highly-ordered sample exhibits Shubnikov - de Haas oscillations which correspond to nonlinearities observed in the Hall resistance, indicating a potential new quantum Hall system. We show that the high-mobility films can be patterned via conventional lithographic techniques, and we demonstrate modulation of the film conductance using a top-gate electrode. These key elements suggest electronic device applications based on nano-patterned epitaxial graphene (NPEG), with the potential for large-scale integration.

290 citations

Journal Article
TL;DR: It is found that the termination of the photonic crystal end facets and an appropriate choice of the wavelength are instrumental in achieving very low numerical apertures.
Abstract: Recently it has been shown that it is possible to achieve directional emission out of a subwavelength aperture in a periodically corrugated metallic thin film. We report on theoretical and experimental studies of a related phenomenon concerning light emitted from photonic crystal waveguides that are less than a wavelength wide. We find that the termination of the photonic crystal end facets and an appropriate choice of the wavelength are instrumental in achieving very low numerical apertures. Our results hold promise for the combination of photonic crystal waveguides with conventional optical systems such as fibers, waveguides, and freely propagating light beams.

214 citations

Book
01 Jan 2003
TL;DR: Comprehensive in scope, and gentle in approach, this book will help you achieve a thorough grasp of the basics and move gradually to more sophisticated DSP concepts and applications.
Abstract: From the Publisher: This is undoubtedly the most accessible book on digital signal processing (DSP) available to the beginner. Using intuitive explanations and well-chosen examples, this book gives you the tools to develop a fundamental understanding of DSP theory. The author covers the essential mathematics by explaining the meaning and significance of the key DSP equations. Comprehensive in scope, and gentle in approach, the book will help you achieve a thorough grasp of the basics and move gradually to more sophisticated DSP concepts and applications.

162 citations

Journal ArticleDOI
TL;DR: In this article, the authors proposed using heterostructures of phosphorene, graphene, and transition metal dichalcogenides to enhance the sensitivity of surface plasmon resonance (SPR) biosensors.
Abstract: Two-dimensional (2-D) materials have attracted a lot of attention for using in surface plasmon resonance (SPR) biosensors. High sensitivity and figure of merit are two desirable parameters in sensor performance analysis. Using heterostructures of phosphorene, graphene, and transition metal dichalcogenides is proposed to enhance the sensitivity of biosensor. Although the proposed biosensor can be used for detection of different analytes with a wide refractive index range, DNA hybridization is the sensing target in this paper. Sensing parameters of different biosensor configurations based on a few-layer black phosphorus (BP) and other 2-D materials are compared with the conventional Au-based SPR sensor and the highest sensitivity of 187°/RIU for the structure consists of 10-layer BP and monolayer WS2 is obtained. The suggested sensor structure provides the sensitivity more than two times of the conventional biosensor. This high sensor performance may have potential applications in medical diagnosis and biochemical detection.

93 citations