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optical-bistability
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Investigating the impact of correlated white noises on the bistability behavior in an optical three-level bistable system
, Article Journal of the Optical Society of America B: Optical Physics ; Volume 32, Issue 1 , 2015 , Pages 76-82 ; 07403224 (ISSN) ; Sadighi Bonabi, R ; Sharif University of Technology
Abstract
The effect of correlated white noises on the optical bistability behavior of three-level atomic systems is theoretically investigated. Noise-induced bistability is demonstrated in an atomic optical bistable system consisting of three-level atoms in Ë-type configurations confined in an optical ring cavity. The output field as a result of enhanced Kerr nonlinearity induced by atomic coherence in the electromagnetically induced transparency system is variable due to the noises in laser parameters and the cooperativity parameter. Therefore, noise is mainly responsible for such induced bistability in the system. It is found that with the cross-correlation noises, the hysteresis loop of optical...
Propagation of Space-Wavepackets in one Dimensional Nonlinear and Nonhomogeneus Structures
, M.Sc. Thesis Sharif University of Technology ; Mehrany, Khashayar (Supervisor)
Abstract
Semi-analytical solutions for the nonlinear, one dimensional wave equation have been investigated. The aim of this procedure is to deliver fast and yet accurate approaches for solving the abovementioned equasions. These solutions make a good alternative for full-numerical methods, which are usually time consuming and combersome. Therefore the proposed methods may find complete priority, considering design goals. Lack of a fast numerical method for solving the nonlinear, steady state cases, make the proposed approaches relevant, dealing theses problems. By employing the presented methods, It is possible to effieciently simulate the behavior of the space-wave packet, incident on the nonlinear...
Investigation of Optical Bistability in Quantum Dot and Erbium Doped Fiber Ring Resonator
, M.Sc. Thesis Sharif University of Technology ; Bahrampour, Alireza (Supervisor)
Abstract
Optical bistability is one of the most important results of nonlinear optics. The term optical bistability refers to the situation in which two different output intensities are possible for a given input intensity. Interest in optical bistability stems from its potential usefulness as a switch for use in optical communication and in optical computing. Optical bistability is resulted by nonlinear phenomena such as kerr effect, two photon absorption and saturable absorber. In this thesis, we study the optical bistability in a double-coupler ring resonator, in which the right half of ring is made of an erbium doped fiber amplifier for compensating the loss by the gain of EDFA, and the left half...
Quantum Interference and Coherence and Electromagnetic Induced Transparency in Multilevel Atomic Systems
, Ph.D. Dissertation Sharif University of Technology ; Sadighi Bonabi, Rasoul (Supervisor)
Abstract
This thesis deals with the theoretical and experimental investigation of quantum interference and coherence, and electromagnetic induced transparency (EIT) in multi-level atomic systems such as hot and cold Rb atoms, semiconductor quantum dots and wells. Optical properties of atomic media in presence of coherent laser fields and incoherent fields are studied.
Theoretical studies verify the crucial role of atomic coherence due to quantum interference in modifying optical properties of atomic media. Suitable and efficient models based on multi-level atomic systems to investigate the optical properties and, optical bistability and multistability are proposed. The most advantages of these...
Theoretical studies verify the crucial role of atomic coherence due to quantum interference in modifying optical properties of atomic media. Suitable and efficient models based on multi-level atomic systems to investigate the optical properties and, optical bistability and multistability are proposed. The most advantages of these...
, M.Sc. Thesis Sharif University of Technology ; Sadighi Bonabi, Rasoul (Supervisor)
Abstract
Quantum interference and coherence could change the optical response of media and results several effect such as electromagnetically induced transparency (EIT), Lasing Without inversion (LWI) and optical nonlinearityenhancement.In Quantum Computing, by using Quantum coherence, one can producedecoherence free sub-space whichhasoutstandingapplications in this field.
In this work optical bistability behavior studied in two coupled quantum dots which resembles a three-level V type atomic system under influence of squeezed state reservoir. Spontaneously generated coherence (SGC) is responsible for Quantum interference. The squeezed state radiation could break the coherence in media and make...
In this work optical bistability behavior studied in two coupled quantum dots which resembles a three-level V type atomic system under influence of squeezed state reservoir. Spontaneously generated coherence (SGC) is responsible for Quantum interference. The squeezed state radiation could break the coherence in media and make...
Analysis of transient response and instability in fiber ring resonators containing an erbium-doped fiber amplifier and quantum dot-doped fiber saturable absorber
, Article Journal of the Optical Society of America B: Optical Physics ; Volume 30, Issue 12 , December , 2013 , Pages 3215-3224 ; 07403224 (ISSN) ; Bahrampour, A. R ; Sharif University of Technology
Optical Society of American (OSA)
2013
Abstract
In this paper, the transient response of a double coupler fiber ring resonator containing an erbium-doped fiber amplifier (EDFA) in half part of the fiber ring resonator and a quantum dot-doped fiber (QDF) saturable absorber in the other half, is investigated. It is demonstrated that, depending on the device parameters and the input power of the signal and pump, various types of dynamic behaviors (such as bistability, monostability, and regenerative pulsation) can be observed in this intrinsic, optical bistable device. The proposed device can be exploited by optical communication networks to realize all-optical functionalities
On the dynamics of bistable micro/nano resonators: Analytical solution and nonlinear behavior
, Article Communications in Nonlinear Science and Numerical Simulation ; Volume 20, Issue 3 , March , 2015 , Pages 1078-1089 ; 10075704 (ISSN) ; Nejat Pishkenari, H ; Hairi Yazdi, M. R ; Maani Miandoab, E ; Sharif University of Technology
Elsevier
2015
Abstract
With the rapid development of micro/nano-electro-mechanical systems (MEMS/NEMS), arch shaped resonators are becoming increasingly attractive for different applications. Nevertheless, the dynamics of bistable resonators is poorly understood, and the conditions for their appropriate performance are not well known. In this paper, an initially curved arch shaped MEMS resonator under combined DC and AC distributed electrostatic actuation is investigated. A reduced order model obtained from first mode Galerkin's decomposition method is used for numerical and analytical investigations. We have used the Homotopy Analysis Method (HAM) in order to derive analytical solutions both for the amplitude and...
Analysis of Nonlinear and Plasmonic Nano-Photonic Structures
, M.Sc. Thesis Sharif University of Technology ; Mehrany, Khashayar (Supervisor) ; Khorasani, Sina (Supervisor)
Abstract
Different methods of shifting and shaping of space-time electromagnetic pulses are in this work investigated by nonlinearity and/or dispersion. Developing two dimensional (2D) finite difference time domain (FDTD) codes in the nonlinear regime and taking the optical dispersion of ideal metals into account, nanophotonic and plasmonic structures are analyzed in this thesis.
Goos-Hänchen shift, superprism effect, and optical bistability are particularly emphasized. A heuristic approximation is presented to extract the Goos-Hänchen shift at the interface of 1D and 2D photonic crystals. The superprism effect for electric polarization – where the electric field vector is perpendicular to the 2D...
Goos-Hänchen shift, superprism effect, and optical bistability are particularly emphasized. A heuristic approximation is presented to extract the Goos-Hänchen shift at the interface of 1D and 2D photonic crystals. The superprism effect for electric polarization – where the electric field vector is perpendicular to the 2D...
Optical bistability via quantum interference from incoherent pumping and spontaneous emission
, Article Journal of Luminescence ; Volume 131, Issue 11 , 2011 , Pages 2395-2399 ; 00222313 (ISSN) ; Asadpour, S. H ; Sadighi Bonabi, R ; Sharif University of Technology
Abstract
We theoretically investigate the optical bistability (OB) in a V-type three-level atomic system confined in a unidirectional ring cavity via incoherent pumping field. It is shown that the threshold of optical bistability can be controlled by the rate of an incoherent pumping field and by interference mechanism arising from the spontaneous emission and incoherent pumping field. We demonstrate that the optical bistability converts to optical multi-stability (OM) by the quantum interference mechanism
Controlling the optical bistability via quantum interference in a four-level N-type atomic system
, Article Journal of Luminescence ; Volume 131, Issue 8 , August , 2011 , Pages 1682-1686 ; 00222313 (ISSN) ; Asadpour, S. H ; Mahrami, H ; Sadighi Bonabi, R ; Sharif University of Technology
2011
Abstract
We investigate the optical bistability (OB) and optical multi-stability (OM) in a four-level N-type atomic system. The effect of spontaneously generated coherence (SGC) on OB and OM is then discussed. It is found that SGC makes the medium phase dependent, so the optical bistability and multi-stability threshold can be controlled via relative phase between applied fields. We realize that the frequency detuning of probe and coupling fields with the corresponding atomic transition plays an important role in creation OB and OM. Moreover, the effect of laser coupling fields and an incoherent pumping field on reduction of OB and OM threshold is then discussed
Size-dependent bistability of an electrostatically actuated arch NEMS based on strain gradient theory?
, Article Journal of Physics D: Applied Physics ; Volume 48, Issue 24 , May , 2015 ; 00223727 (ISSN) ; Pishkenari, H. N ; Yazdi, M. R. H ; Miandoab, E. M ; Sharif University of Technology
Institute of Physics Publishing
2015
Abstract
This paper deals with the investigation of the size-dependent nature of nonlinear dynamics, in a doubly clamped shallow nano-arch actuated by spatially distributed electrostatic force. We employ strain gradient theory together with the Euler-Bernoulli and shallow arch assumptions in order to derive the nonlinear partial differential equation governing the transverse motion of the arch with mid-plane stretching effects. Using the Galerkin projection method, we derive the lumped single degree of freedom model which is then used for the study of the size effects on the nonlinear snap-through and pull-in instabilities of the arch nano-electro-mechanicalsystem (NEMS). Moreover, using strain...
Optical bistable switching with Kerr nonlinear materials exhibiting a finite response time in two-dimensional photonic crystals
, Article Volume 7713 ; Proceedings of SPIE - The International Society for Optical Engineering, 12 April 2010 through 15 April 2010 , 2010 ; 0277786X (ISSN) ; 9780819481863 (ISBN) ; Monem Haghdoost, Z ; Abediasl, H ; Khorasani, S ; Mehrany, K ; Sharif University of Technology
Abstract
Effect of relaxation time on the performance of photonic crystal optical bistable switches based on Kerr nolinearity is discussed. This paper deals with optical pulses with the duration of about 50 ps. In such cases the steady state response of the optical device can be used to approximate the pulse evolution if the nonlinearity is assumed instantaneous, hence analytical solutions such as the coupled mode theory can be used to obtain the time evolution of the electromagnetic fields. However if the relaxation time of the material nonlinear response is also considered, changes in the power levels and in the shape of the hystersis loop is observed. In this case, we use the nonlinear finite...
On the chaotic vibrations of electrostatically actuated arch micro/nano resonators: a parametric study
, Article International Journal of Bifurcation and Chaos ; Volume 25, Issue 8 , July , 2015 ; 02181274 (ISSN) ; Hairi Yazdi, M. R ; Nejat Pishkenari, H ; Sharif University of Technology
World Scientific Publishing Co. Pte Ltd
2015
Abstract
Motivated by specific applications, electrostatically actuated bistable arch shaped micro-nano resonators have attracted growing attention in the research community in recent years. Nevertheless, some issues relating to their nonlinear dynamics, including the possibility of chaos, are still not well known. In this paper, we investigate the chaotic vibrations of a bistable resonator comprised of a double clamped initially curved microbeam under combined harmonic AC and static DC distributed electrostatic actuation. A reduced order equation obtained by the application of the Galerkin method to the nonlinear partial differential equation of motion, given in the framework of Euler-Bernoulli beam...
Optimum operation of single cavity photonic switches
, Article Proceedings of SPIE - The International Society for Optical Engineering, 25 January 2010 through 27 January 2010 ; Volume 7607 , January , 2010 ; 0277786X (ISSN) ; 9780819480033 (ISBN) ; Monem Haghdoost, Z ; Edalatipour, M ; Khorasani, S ; Mehrany, K ; Sharif University of Technology
2010
Abstract
In this work, an optimum frequency is found for the operation of single cavity photonic switches. At this optimum point, the transmission contrast of ON and OFF states takes its highest value, while keeping the device power threshold relatively low and the device speed acceptably high. Then, the dynamic behavior of a typical single cavity all optical switch is investigated in the optimum operation point through temporal Coupled Mode Theory. Switching speed and power are discussed, and the device is shown to be applicable for telecommunication and data processing applications. The analysis is quite general, and can be used for resonant structures, such as photonic crystals and microring...
On the power-bandwidth trade-off in bistable photonic switches
, Article Photonic and Phononic Crystal Materials and Devices IX, San Jose, CA, 27 January 2009 through 29 January 2009 ; Volume 7223 , 2009 ; 0277786X (ISSN) ; Abediasl, H ; Mehrany, K ; Khorasani, S ; Chamanzar, M. R ; Adibi, A ; Sharif University of Technology
2009
Abstract
Low power operation and high speed have always been desirable in applications such as data processing and telecommunications. While achieving these two goals simultaneously, however, one encounters the well-known powerbandwidth trade-off. This is here discussed in a typical bistable switch based on a two-dimensional photonic crystal with Kerr type nonlinearity. The discussion is supported by the nonlinear finite difference time domain (FDTD) simulation of a direct coupled structure with a home-developed code. Two cases of working near resonant and off- resonant are simulated to compare the power and the speed of the device in the two cases. It is shown that working nearresonance reduces the...
All-optical flip-flop composed of a single nonlinear passive microring coupled to two straight waveguides
, Article Optics Communications ; Volume 282, Issue 3 , 2009 , Pages 427-433 ; 00304018 (ISSN) ; Mirzaee, M. A ; Farman, F ; Zakeri, S ; Sharif University of Technology
2009
Abstract
Microrings can have different hysteresis characteristics at their different resonance frequencies. They can be used as a multi-hysteresis optical component. In this paper an optical D-flip-flop circuit composed of a single nonlinear passive microring coupled to two straight waveguide based on the Kerr effect is proposed. The proposed circuit can operate as an optical digital circuit which synchronizes input DATA with the CLOCK of the circuit. A simple analytical model for hysteresis design and the transient analysis of the proposed D-flip-flop are presented. According to our model, the switching time of the flip-flop is in the order of 10 ps. Crown Copyright © 2008
All-optical set-reset flip-flop based on the passive microring-resonator bistability
, Article Optics Communications ; Volume 281, Issue 20 , 2008 , Pages 5104-5113 ; 00304018 (ISSN) ; Karimi, M ; Abolfazli Qamsari, M. J ; Rooholamini Nejad, H ; Keyvaninia, S ; Sharif University of Technology
2008
Abstract
In this paper, we propose a design for an all-optical R-S flip-flop with separate set and reset inputs, which is based on the optical bistability due to Kerr and two-photon absorption (TPA) effects in the microring resonators. Based on the steady state analysis of the light propagation in nonlinear microrings, variations of hysteresis parameters versus the system variables, such as transmission coefficient, nonlinear refractive index and detuning angle, are analyzed. The switching temporal behavior of the proposed flip-flop is obtained by the microring transient analysis. It is shown that the contrast ratio parameter and the switching power of the proposed all-optical flip-flop can be...
Piecewise affine large signal modeling of PFC rectifiers
, Article 2007 IEEE International Symposium on Industrial Electronics, ISIE 2007, Caixanova - Vigo, 4 June 2007 through 7 June 2007 ; 2007 , Pages 3362-3366 ; 1424407559 (ISBN); 9781424407552 (ISBN) ; Molla Ahmadian, H ; Sharif University of Technology
2007
Abstract
A problem associated with modeling and control of the power factor correction rectifiers is that the ac variations in duty cycle, as well as in the ac input voltage and current are not small, and hence the traditional small signal analysis is not justified. Nonetheless, the low-frequency components of the converter can be modeled via the circuit averaging technique, but the resulting equivalent circuits are, in general, time varying and highly nonlinear. Nonlinear stability analysis methods are not appropriate for analysis and control design of such complicated circuits. In this paper a piecewise affine approximation is introduced for modeling of switching circuits. This approach makes the...