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Performance Analysis and Optimization of Optically Steered Arrayed Antennas with Gratings
, Ph.D. Dissertation Sharif University of Technology ; Akbari, Mahmood (Supervisor)
Abstract
It is well known that arrays of antennas make it possible to steer the radiation pattern without steering a physical structure. For the past few decades this has been considered for many civil and military communication systems. Recently, ultra-short pulses are considered for high resolution radars and ultra-wideband communication systems. Systems with short pulses and large antenna arrays may benefit from high resolution in both temporal and spatial domains. But the implementation of the ultra-wideband feeding circuits for such antenna arrays is a hard job even with state of the art electronics. Optical technology has been applied, successfully, to a number of radio applications such as...
Nonreciprocal behaviour between photon and phonon in coupled optomechanical systems
, Article Journal of Modern Optics ; Volume 64, Issue 5 , 2017 , Pages 507-514 ; 09500340 (ISSN) ; Zandi, M. H ; Bahrampour, A ; Sharif University of Technology
Taylor and Francis Ltd
2017
Abstract
It is shown that the asymmetry coupling between two coupled optomechanical cavities leads to special class of PT-symmetric model for optomechanical structure. Under these conditions, Hamiltonian is considered in blue and red sideband regime. In these cases, the asymmetric coupling between two cavities has been transferred such that the asymmetric beam-splitter or squeezing interaction is generated between optical and mechanical modes. Then, the amount of entanglement between the different optical and mechanical modes is calculated. The results define that PT-symmetry can improve the entanglement in special conditions. The proposed system provides good condition to investigate the...
Performance analysis of an optical beam-forming network with custom microwave CAD tools
, Article Proceedings - 2010 18th Iranian Conference on Electrical Engineering, ICEE 2010, 11 May 2010 through 13 May 2010, Isfahan ; 2010 , Pages 100-104 ; 9781424467600 (ISBN) ; Akbari, M ; Sharif University of Technology
Abstract
Next generation wideband and ultra-wideband radar antenna arrays need efficient true-time delay networks for array control. Optical beam-forming networks have been considered as a promising solution in such arrays. Performance analysis of optical beam-formers is thus quiet necessary. In this paper signal to noise ratio and dynamic range of simple optical beam-forming structures are investigated with a custom microwave CAD tool. Two structures with optical and RF power combining methods are discussed. With the proposed devices' parameters, the optical combining method shows better performance for low and moderate optical powers
Quantum interface between optics and microwaves with optomechanics
, Article 2013 Conference on Lasers and Electro-Optics Europe and International Quantum Electronics Conference, CLEO/Europe-IQEC 2013, Munich, 12 May 2013 through 16 May 2013 ; 2013 ; Abdi, M ; Milburn, G. J ; Tombesi, P ; Vitali, D ; Sharif University of Technology
IEEE Computer Society
2013
Abstract
A number of schemes for a quantum interface between light at different wavelengths have been demonstrated and very recently various solutions for interfacing optics and microwaves have been proposed [1-3]. We describe here a reversible quantum interface between optical and microwave photons based on a micro-mechanical resonator in a superconducting circuit, simultaneously interacting with an optical and a microwave cavity [3]. When the cavities are appropriately driven, the mechanical resonator mediates an effective parametric amplifier interaction, entangling an optical signal and a microwave idler. Such continuous variable (CV) entanglement can be then exploited to implement CV...
Effects of group delay ripple on optical beam-formers for pulsed antenna arrays
, Article Optical and Quantum Electronics ; Volume 43, Issue 6-10 , November , 2012 , Pages 109-120 ; 03068919 (ISSN) ; Akbari, M ; Sharif University of Technology
Springer New York LLC
2012
Abstract
A semi-analytical formulation is presented to quantify the effects of group delay ripple on the performance of an optical beam-former. For delay elements, implemented with commercially available multi-channel fiber Bragg gratings, an impulse response is introduced and calculated for the group delay ripple. To do this, the transfer function of the fiber Bragg grating is parted into two dispersive and non-dispersive sections. This will also easethe demonstration of the fiber Bragg grating as a true time delay element. The formulation is applied to an ultra-wideband pulsed array of antennas. As an example the array factor and electric field patterns of a four element antenna array is derived,...
Flat-top beam profile generated using a fiber-bundle prism-coupled beam shaper
, Article Optics Communications ; Volume 284, Issue 12 , June , 2011 , Pages 2817-2824 ; 00304018 (ISSN) ; Golnabi, H ; Sharif University of Technology
2011
Abstract
In this paper, an optical beam shaping system is theoretically and experimentally investigated. The optical system design software ZEMAX is used to simulate and analyze the reported beam shaping design. By using this software ray tracing diagrams are presented with the aim of studying the direct beam propagation, total reflection rays, and the lost rays. The prism duct output beam shape and radiance profiles in both position space and angle space are also studied. For experimental investigation, a two-stage beam shaping design including a fiber-bundle and a prism duct is used. A source light is used for the fiber-bundle illumination and the photograph image of the output beam is taken by a...
An investigation on the performance of receiving optical beam-forming networks
, Article Final Program and Book of Abstracts - iWAT 2010: 2010 International Workshop on Antenna Technology: Small Antennas, Innovative Structures and Materials, 1 March 2010 through 3 March 2010 ; March , 2010 ; 9781424448845 (ISBN) ; Akbari, M ; Sharif University of Technology
2010
Abstract
Next generation wideband and ultra-wideband radar antenna arrays need efficient true-time delay networks for array control. Following the great interest for optical control of antenna array beam steering, performance analysis of optical beam-formers is a must. In this paper signal to noise ratio and dynamic range of simple optical beamforming structures with components off the shelf are investigated theoretically. Especially the effects of certain power combining components such as arrayed wave guide gratings, broadband passive optical combiners and microwave combiners inspected. It turns up that an efficient microwave combiner would surpass the optical combiners in both SNR and dynamic...
Wideband and narrowband circuit models for fano-shape guided-mode resonance
, Article IEEE Journal of Quantum Electronics ; Volume 55, Issue 3 , 2019 ; 00189197 (ISSN) ; Memarian, M ; Mehrany, K ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
In this paper, we propose two different types of circuit models for Fano-shape guided-mode resonance (GMR) in waveguide gratings. Both the models constitute a resonant tank circuit together with a direct non-resonant channel between the incident and scattered light. One neglects the frequency dependence of the direct non-resonant channel and is only more accurate in the immediate vicinity of the Fano-type resonance. The other accounts for the frequency dependence of the direct non-resonant channel and thus remains accurate within a wider range of frequencies. The former being referred to as the narrow-band model is extremely accurate, insofar as the isolated GMR is of interest within a...
Wide-and narrow-band circuit models for fano-shape guided mode resonance
, Article IEEE Journal of Quantum Electronics ; 2019 ; 00189197 (ISSN) ; Memarian, M ; Mehrany, K ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
In this paper, we propose two different types of circuit models for Fano-shape guided mode resonance (GMR) in waveguide gratings. Both models constitute a resonant tank circuit together with a direct non-resonant channel between the incident and the scattered light. One neglects the frequency dependence of the direct non-resonant channel and is only more accurate in the immediate vicinity of the Fano type resonance. The other accounts for the frequency dependence of the direct non-resonant channel and thus remains accurate within a wider range of frequencies. The former being referred to as the narrow-band model is extremely accurate insofar as the isolated GMR is of interest within a narrow...
Wide-and narrow-band circuit models for fano-shape guided mode resonance
, Article IEEE Journal of Quantum Electronics ; 2019 ; 00189197 (ISSN) ; Memarian, M ; Mehrany, K ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
In this paper, we propose two different types of circuit models for Fano-shape guided mode resonance (GMR) in waveguide gratings. Both models constitute a resonant tank circuit together with a direct non-resonant channel between the incident and the scattered light. One neglects the frequency dependence of the direct non-resonant channel and is only more accurate in the immediate vicinity of the Fano type resonance. The other accounts for the frequency dependence of the direct non-resonant channel and thus remains accurate within a wider range of frequencies. The former being referred to as the narrow-band model is extremely accurate insofar as the isolated GMR is of interest within a narrow...
Three-dimensional finite-difference time-domain analysis of gas ionization
, Article 2008 International Symposium on Telecommunications, IST 2008, Tehran, 27 August 2008 through 28 August 2008 ; October , 2008 , Pages 157-162 ; 9781424427512 (ISBN) ; Shishegar, A. A ; Sharif University of Technology
2008
Abstract
The propagation of intense optical beams in a gas undergoing ionization is analyzed through a threedimensional finite-difference time-domain (3D-FDTD) scheme. The propagation dynamics include the effects of diffraction, nonlinear self-focusing, and ionization. For sufficiently intense optical beams the neutral gas undergoes ionization, generating a plasma which tends to defocus the beam. Balancing of diffraction, plasma defocusing, and nonlinear self-focusing may lead to self-guided results. In this paper, necessary relations have been introduced into the conventional FDTD formulation to account for the nonlinear behaviors. Furthermore, a concurrent utilization of computer memory and disk...
Beam shape and intensity profile of a fiber-bundle prism-coupled waveguide
, Article Optics and Lasers in Engineering ; Volume 48, Issue 6 , June , 2010 , Pages 720-726 ; 01438166 (ISSN) ; Haghighatzadeh, A ; Sharif University of Technology
2010
Abstract
Design and performance of a two-stage optical beam shaping system based on a plastic fiber-bundle prism-coupled waveguide is described in this study. Such systems offer practical means to modify and change the output beam shape at two stages and also provide quantitative information concerning the output beam intensity profile. It is possible to obtain reflection and image transmittance data by using a light source for the illumination and image analysis by a CCD/digital camera. Using the active lighting, the reflection data and image profiles for the output beam are obtained by a CCD camera and presented in this study. The photograph picture of the illuminating LED beam just at its output...