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optoelectronics
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Beam manipulating by gate-tunable graphene-based metasurfaces
, Article Optics Letters ; Volume 40, Issue 22 , 2015 , Pages 5383-5386 ; 01469592 (ISSN) ; Arik, K ; Farajollahi, S ; Khavasi, A ; Kavehvash, Z ; Sharif University of Technology
OSA - The Optical Society
2015
Abstract
We propose an unprecedented transmit-array configuration which can mold the incident beam by modulating phase and amplitude wavefronts. The transmit-array is composed of patterned graphene metasurfaces as shunt admittance sheets. Thanks to the exceptional features of graphene such as tunability, thinness, low loss, and high confinement of graphene plasmons, the proposed subwavelength structure passes strict touchstones for nano-photonic and optoelectronic applications. Two flat-optics functionalities, i.e., focusing and splitting, are realized by means of the proposed configuration
Analytic performance evaluation of OTIS-hypercubes
, Article IEICE Transactions on Information and Systems ; Volume E89-D, Issue 2 , 2006 , Pages 441-451 ; 09168532 (ISSN) ; Sarbazi Azad, H ; Sharif University of Technology
Institute of Electronics, Information and Communication, Engineers, IEICE
2006
Abstract
In this paper, routing properties of cube-based optoelectronic OTIS networks are explored. We show emulations of various cubical network topologies on their OTIS augmented variants, including the nD grid networks, shuffle-exchange, and de Brujin networks. An analytical performance model for OTIS-cube networks is proposed. The model is validated by means of comparison with rigorously obtained simulation results. Using this model, the performance characteristics of the OTIS-hypercube network are evaluated in view of a number of different constraints. Moreover, we compare the performance characteristics of the OTIS-hypercube with that of equivalent fully-electronic networks under various...
Effect of bromine doping on the charge transfer, ion migration and stability of the single crystalline MAPb(Br: XI1- x)3photodetector
, Article Journal of Materials Chemistry C ; Volume 9, Issue 42 , 2021 , Pages 15189-15200 ; 20507534 (ISSN) ; Prochowicz, D ; Kruszyńska, J ; Satapathi, S ; Akin, S ; Kumari, H ; Kumar, P ; Fazel, Z ; Tavakoli, M. M ; Yadav, P ; Sharif University of Technology
Royal Society of Chemistry
2021
Abstract
Organic-inorganic halide perovskites (OIHPs) have emerged as a promising semiconductor for the fabrication of efficient optoelectronic devices such as photodetectors (PDs). Among all the perovskite compositions, the mixed-halide MAPb(BrxI1-x)3 formulations have gained more attention for photodetection application thanks to their tunable optoelectronic properties and great stability. However, there is still a lack of sufficient understanding of the effect of Br doping on the stability and physical properties of MAPb(BrxI1-x)3 based PDs. In this work, we prepare a series of MAPb(BrxI1-x)3 (x = 0, 0.04, 0.08, 0.12, and 0.16) single crystals (SCs) and investigate the influence of the Br content...
Analytical prediction of the main oscillation power and spurious levels in optoelectronic oscillators
, Article Journal of Lightwave Technology ; Vol. 32, issue. 5 , 2014 , pp. 978-985 ; ISSN: 07338724 ; Banai, A ; Sharif University of Technology
Abstract
We use a nonlinear analytic approach to predict the main oscillation mode power and spurious levels in ultrapure microwave optoelectronic oscillators (OEOs). This approach takes into account N simultaneously mode falling inside the RF filter bandwidth and calculates all the dominant InterModulation Products (IMPs) that fall in the fundamental zone. We show that nonlinear microwave photonic links exhibit the capture effect. By considering this effect, we derive analytical expressions that govern the behavior of the OEOs in the steady state. We find that when the small-signal open-loop gain is increased beyond a critical value, OEOs start a multimode operation from which the spurious levels...
Mathematical performance modelling of adaptive wormhole routing in optoelectronic hypercubes
, Article Journal of Parallel and Distributed Computing ; Volume 67, Issue 9 , Volume 67, Issue 9 , 2007 , Pages 967-980 ; 07437315 (ISSN) ; Sarbazi Azad, H ; Sharif University of Technology
2007
Abstract
In this paper, an analytical performance model for adaptive wormhole routing in the hypercube-based optical transpose interconnection system (OTIS-hypercube) is proposed and validated. Using this model, the performance merits of the OTIS-hypercube are discussed. We also compare the performance of the OTIS-hypercube with that of equivalent hypercube network under different implementation constraints. Compared to pure simulation results, the presented model can serve as a more appropriate and compact method to display the performance characteristics of OTIS-hypercube networks. © 2007 Elsevier Inc. All rights reserved
Effect of content silver and heat treatment temperature on morphological, optical, and electrical properties of ITO films by sol-gel technique
, Article Journal of Nanoparticle Research ; Volume 16, Issue 9 , September , 2014 ; ISSN: 13880764 ; Dolati, A ; Sharif University of Technology
Abstract
Silver-doped indium tin oxide thin films were synthesized using sol-gel dip-coating technique. The influence of different silver-dopant contents and annealing temperature on the electrical, optical, structural, and morphological properties of the films were characterized by means of four-point probe, UV-Vis spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and X-ray photoelectron spectroscope (XPS). XRD analysis confirmed the formation of cubic bixbyte structure of In2O3with silver nanoparticles annealed at 350 °C. XPS analysis showed that divalent tin transformed to tetravalent tin through oxidization, and silver nanoparticles embedded into ITO...
An empirical performance analysis of minimal and non-minimal routing in cube-based OTIS multicomputers
, Article Journal of High Speed Networks ; Volume 16, Issue 2 , 2007 , Pages 133-155 ; 09266801 (ISSN) ; Sarbazi Azad, H ; Sharif University of Technology
2007
Abstract
In this study, the performance of virtual cut-through switching in the cube-based OTIS architecture, an optoelectronic interconnection architecture for multicomputer systems, is empirically analyzed. Deadlock-free deterministic and adaptive minimal path routing algorithms for this architecture are introduced, and the effects of different network and traffic parameters on average message latency are investigated. This analysis presents a relatively more realistic view of the OTIS architecture than that presented in previous work by considering issues related to a lower level of abstraction (the routing and switching of messages). Among other results, the analysis indicates that depending on...
Multicast communication in OTIS-hypercube multi-computer systems
, Article International Journal of High Performance Computing and Networking ; Volume 4, Issue 3-4 , 2006 , Pages 161-173 ; 17400562 (ISSN) ; Sarbazi azad, H ; Sharif University of Technology
2006
Abstract
The ability to perform multicast communication efficiently in parallel computing systems is increasingly becoming an essential feature of these systems. Therefore, any emerging parallel architecture must be able to provide effective multicasting performance. OTIS-based multi-computer systems are parallel systems that efficiently exploit optical connections between distant nodes, while using electronic connections for physically close processors. No previous work has attempted to determine an optimal multicast communication scheme for OTIS networks. This paper presents two approaches to implement efficient multicast communication in wormhole-routed OTIS networks, for the two different...
Plasmonic enhancement of photocurrent generation in two-dimensional heterostructure of WSe2/MoS2
, Article Nanotechnology ; Volume 32, Issue 32 , 2021 ; 09574484 (ISSN) ; Esfandiar, A ; Sharif University of Technology
IOP Publishing Ltd
2021
Abstract
Enhancing the photoresponse of single-layered semiconductor materials is a challenge for high-performance photodetectors due to atomically thickness and limited quantum efficiency of these devices. Band engineering in heterostructure of transition metal chalcogenides (TMDs) can sort out part of this challenge. Here, we address this issue by utilizing the plasmonics phenomenon to enrich the optoelectronics property of the WSe2/MoS2 heterojunction and further enhancement of photoresponse. The introduced approach presents a contamination-free, tunable and efficient way to improve light interactions with heterojunction devices. The results showed a 3600-fold enhancement in photoresponsivity and...
An empirical comparison of OTIS-mesh and OTIS-hypercube multicomputer systems under deterministic routing
, Article 19th IEEE International Parallel and Distributed Processing Symposium, IPDPS 2005, Denver, CO, 4 April 2005 through 8 April 2005 ; Volume 2005 , 2005 ; 0769523129 (ISBN); 0769523129 (ISBN); 9780769523125 (ISBN) ; Sarbazi azad, H ; Sharif University of Technology
2005
Abstract
In optoelectronic OTIS architectures, electrical and optical interconnects are used for local and global communication, respectively. Interesting instances of the OTIS architecture are the OTIS-hypercube and OTIS-mesh. This paper conducts a performance evaluation and comparison of these networks under different structural conditions and traffic loads. All judgments made, are based on observations from extensive simulation results of the interconnection networks. We conclude that, when the OTIS-hypercube and equivalent 2-D OTIS-mesh are compared under the constraint of equal bisection bandwidth, the performance of the OTIS-hypercube is of superior performance. We however show that the...
Analysis and Simulation of Micrometre-scale Silicon Electro-optic Modulators Based on Ring Resonators
, M.Sc. Thesis Sharif University of Technology ; Akbari, Mahmood (Supervisor)Fabrication of A Compliant Based 6-DOF Micro Actuator
, M.Sc. Thesis Sharif University of Technology ; Alasty, Areya (Supervisor)
Abstract
Currently, precision positioning plays a pivotal role in technology. The need for accurate positioning in applications such as robotics, optoelectronics and micro and nano technology increases day by day. To begin with, we wanted to make a miniature prototype of a micro actuator but in this regard, we are faced with several problems. Some major problems were the high cost of this prototype plus the fact that we did not have the necessary equipment with acceptable resolution for making such a system, so we decided to decrease the scale and build it in micro scale which is accessible for us. The main idea and design of this micro actuator is by Mrs. Akbari. During this project, the researcher...
Prediction of the noise spectrum in optoelectronic oscillators: An analytical conversion matrix approach
, Article Journal of the Optical Society of America B: Optical Physics ; Vol. 31, issue. 8 , August , 2014 , p. 1915-1925 ; ISSN: 07403224 ; Hosseini, S. E ; Banai, A ; Sharif University of Technology
Abstract
In this paper an analytical formulation based on the conversion matrix approach for characterizing the oscillator noise spectra as well as the phase and amplitude noise spectra for a single-loop optoelectronic oscillator (OEO) is presented. The validity of this approach is verified by comparing our results regarding the noise spectra of the OEO against the results of two references in the literature. The first reference presents simulation results, and the second reference presents both simulation and measurement results, and good agreement is seen between the results of the new method and those of the references. The advantage of the new approach is the simplicity of the theory as well as...
Evidence for nonradiative energy transfer in graphene-oxide-based hybrid structures
, Article Journal of Physical Chemistry C ; Volume 117, Issue 48 , December , 2013 , Pages 25298-25304 ; 19327447 (ISSN) ; Kucukayan-Dogu, G ; Guzelturk, B ; Fardindoost, S ; Kelestemur, Y ; Demir, H. V ; Sharif University of Technology
2013
Abstract
Solution processed graphene variants including graphene oxide (GO) and reduced graphene oxide (RGO) are promising materials for potential optoelectronic applications. To date, efficiency of the excitation energy transfer into GO and RGO thin layers has not been investigated in terms of donor-acceptor separation distance. In the present work, we study nonradiative energy transfer (NRET) from CdSe/CdS quantum dots into single and/or double layer GO or RGO using time-resolved fluorescence spectroscopy. We observe shorter lifetimes as the separation distance between the QDs and GO or RGO decreases. In accordance with these lifetimes, the rates reveal the presence of two different mechanisms...
Theoretical investigation of the capture effect in intensity-modulation direct-detection microwave photonic links
, Article Applied Optics ; Volume 52, Issue 28 , 2013 , Pages 7011-7021 ; 1559128X (ISSN) ; Banai, A ; Sharif University of Technology
Optical Society of American (OSA)
2013
Abstract
We introduce the capture effect concept in microwave photonic links (MWPLs) for the first time to our knowledge. The capture effect or the small-signal suppression is the change in the amplitude ratio of the two signals between input and output of the intensity-modulation direct-detection (IMDD) MWPLs. An analytical explanation of the performance of external IMDD MWPLs due to the effects of nonlinearity combined with sum of several input sinusoidal signals is given.We have investigated the suppression of a weaker signal in these links. General analytic expression for the small-signal suppression is derived using a nonlinear analytical approach. We show that the small-signal suppression is...
Geometrical approach in physical understanding of the Goos-Haenchen shift in one- And two-dimensional periodic structures
, Article Optics Letters ; Volume 33, Issue 24 , 2008 , Pages 2940-2942 ; 01469592 (ISSN) ; Naqavi, A ; Khavasi, A ; Mehrany, K ; Khorasani, S ; Rashidian, B ; Sharif University of Technology
Optical Society of America (OSA)
2008
Abstract
The Goos-Haenchen shift of a totally reflected beam at the planar interface of two dielectric media, as if the incident beam is reflected from beneath the interface between the incident and transmitted media, has been geometrically associated with the penetration of the incident photons in the less-dense forbidden transmission region. This geometrical approach is here generalized to analytically calculate the Goos-Haenchen shift in one- and two-dimensional periodic structures. Several numerical examples are presented, and the obtained results are successfully tested against the well-known Artman's formula. The proposed approach is shown to be a fast, simple, and efficient method that can...
Differential-transfer-matrix based on Airy's functions in analysis of planar optical structures with arbitrary index profiles
, Article IEEE Journal of Quantum Electronics ; Volume 44, Issue 4 , February , 2008 , Pages 324-330 ; 00189197 (ISSN) ; Sarrafi, P ; Mehrany, K ; Rashidian, B ; Sharif University of Technology
2008
Abstract
A novel analytical method for solution of planar optical structure with arbitrary refractive index profile is proposed. This new method is founded on differential-transfer-matrices, whose field solutions are based on Airy's trial functions. In contrast to conventional Wentzel, Kramers, and Brillouin (WKB) solutions, which diverge around the turning points, this approach can be successfully used for exact calculation of various functions, including eigenvalues of optical waveguides with arbitrary index profiles, and complex reflection and transmission coefficients, even at the presence of turning points. The method is rigorous and can be applied for both major polarizations. © 2008 IEEE
Photonic band structure of abrikosov lattices in superconductors
, Article Photonic Crystal Materials and Devices VI, San Jose, CA, 22 January 2007 through 25 January 2007 ; Volume 6480 , 2007 ; 0277786X (ISSN) ; Kokabi, A ; Jafarpour, A. A ; Khorasani, S ; Fardmanesh, M ; Adibi, A ; Sharif University of Technology
2007
Abstract
We have performed a numerical solution for band structure of an Abrikosov vortex lattice in type-11 superconductors forming a periodic array in two dimensions for applications of incorporating the photonic crystals concept into superconducting materials with possibilities for optical electronics. The implemented numerical method is based on the extensive numerical solution of the Ginzburg-Landau equation for calculating the parameters of the two-fluid model and obtaining the band structure from the permittivity, which depends on the above parameters and the frequency. This is while the characteristics of such crystals highly vary with an externally applied static normal magnetic field,...
Analysis and simulation of ring resonator silicon electro-optic modulators based on PN junction in reverse bias
, Article Optical Engineering ; Vol. 53, issue. 12 , 2014 ; ISSN: 00913286 ; Akbari, M ; Sharif University of Technology
Abstract
The theory of silicon optical modulators of ring resonators based on PN diode in reverse bias is primarily discussed. It secondarily provides a full-featured simulator to investigate the behavior of such modulators. Wave equation for ring structure will be solved by using the conformal transformation method and the matrix method as it was used to analyze bent planar optical waveguides. Power coupling between ring and straight waveguides will be calculated by coupled theory of nonparallel waveguides based on experimental results. The time response demonstrates the capability of this device to operate correctly at up to 10 Gbs-1 bitrate, and the frequency spectrum analysis of device shows a >...
Low-drift optoelectronic oscillator based on a phase modulator in a sagnac loop
, Article IEEE Transactions on Microwave Theory and Techniques ; Volume 65, Issue 7 , 2017 , Pages 2617-2624 ; 00189480 (ISSN) ; Banai, A ; Kartner, F. X ; Sharif University of Technology
Abstract
A low-drift optoelectronic oscillator (OEO) is developed and experimentally shown. In the proposed OEO, a fiber Sagnac interferometer, including an optical phase modulator (PM) and a nonreciprocal bias unit, functions as an intrinsically drift-free intensity modulator. The phase noise of the proposed OEO is modeled in phase space, which is verified by experiments. Phase noise and frequency stability of the photonically generated microwave signals are measured. The single-sideband phase noise of the generated microwave signal is -106.6 dBc/Hz at 10-kHz offset from the 10.833-GHz carrier, with 120-fs rms timing jitter integrated from 1 kHz to 10 MHz. Frequency drift measurements show ±0.85-ppm...