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bahrampour--fatemeh
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Dynamical Behavior and Stability of Two Semiconductor Micro-ring Lasers in the Presence of Optical Feedback
, M.Sc. Thesis Sharif University of Technology ; Bahrampour, Alireza (Supervisor)
Abstract
Optical memories are key elements in integrated photonics circuits. Semiconductor micro-ring lasers are good candidates in designing and constructing optical memories. Designing of these memories are usually inactive and are based on nonlinear optics such as Kerr effect or saturation absorption. Bifurcation analyses show that semiconductor micro-ring lasers coupled with waveguide, in the presence of external feedback, have two stable modes. At the coupling point, clockwise and counter clockwise states for one mode have zero and for another mode have π phase differences. In this project, by using boundary conditions, we obtain resonance frequency of a system of two semiconductor lasers in the...
Controllable single-mode random laser using stimulated Raman gain
, Article Optics Letters ; Vol. 39, issue. 15 , August , 2014 , pp. 4537-4540 ; ISSN: 01469592 ; Mirzaei, A ; Bahrampour, A ; Sharif University of Technology
2014
Abstract
The present study demonstrates numerically a novel approach to perform a controllable single-mode random laser, using stimulated Raman gain. Due to the narrow linewidth of the Raman line shape, only one of the modes of the passive random system can lase. The robust control on the emission spectrum was achieved through the selection of any desired quasi-modes, by adjusting the pump wavelength in order to place the center of Raman line shape on desired quasi-modes. This approach was proved using a developed nonlinear transfer matrix method for a 1D Raman random system. The proposed method includes the Raman gain saturation and the frequency-dependent index of refraction
Raman random laser in one-dimensional system
, Article Journal of the Optical Society of America B: Optical Physics ; Vol. 31, Issue. 6 , 2014 , Pages 1308-1315 ; ISSN: 07403224 ; Shojaie, E ; Sani, M ; Sharif University of Technology
2014
Abstract
The probability of occurrence of random cavities' resonance frequency in the Stokes bandwidth of the Raman active medium can cause Raman laser oscillation in the random structures. Due to the small bandwidth of Raman line shape, the probability of the simultaneous appearance of random cavity resonance frequencies in the cascade Stokes line shapes is small. As a result, the cascade Raman laser oscillation effects on the saturation behavior are negligible. The nonlinear transmission matrix method is employed to determine the statistical behavior of a Raman random laser. Our results showed that the statistical behavior depends on the position of the Stokes line shape relative to the center of...
Development of a non-invasive micron sized blood glucose sensor based on microsphere stimulated raman spectroscopy
, Article Sensors and Transducers ; Volume 147, Issue 12 , 2012 , Pages 129-142 ; 17265479 (ISSN) ; Jahangiri, N ; Taraz, M ; Sharif University of Technology
2012
Abstract
We proposed a new method for Non-invasive measuring of blood glucose levels by using micro sphere Stimulated Raman scattering. We show that this method can be used to measure biological glucose levels with low power lasers. The field enhancement due to the resonance condition of high quality factor microsphere causes to reduce stimulated Raman scattering thresholds of its surrounding media (glucose) and hence observing stimulated Raman scattering with low power. The results from theoretical studies indicate that the stimulated Raman signal amplitude levels produced from the very low Glucose concentrations. By measuring the changes of the signal intensity in output of fiber, we can determine...
Creation of twisted terahertz waves carrying orbital angular momentum via a plasma vortex
, Article Journal of Physics D: Applied Physics ; Volume 49, Issue 29 , 2016 ; 00223727 (ISSN) ; Rooholamininejad, H ; Bahrampour, A ; Sharif University of Technology
Institute of Physics Publishing
2016
Abstract
In this paper a new method for generating twisted terahertz radiation is proposed. The generation of twisted terahertz radiation in a plasma vortex, where the plasma density profile has helical structure, is investigated. The method is described on the basis of angular momentum exchange between plasma vortex and laser beam. The interaction of the vortex plasma and photons causes the laser angular momentum to change. Twisted terahertz radiation is produced at the beat frequency of laser and electron plasma waves. In this process, for Gaussian laser modes, the angular momentum of terahertz wave derives from the plasma vortex, while for the Laguerre-Gaussian it originates in the difference in...
Resonant second harmonic generation in plasma by self-focused twisted beam
, Article Optics Communications ; Volume 341 , April , 2015 , Pages 295-301 ; 00304018 (ISSN) ; Sohailya, S ; Bahrampour, A ; Sharif University of Technology
Elsevier
2015
Abstract
The resonant second harmonic generation in the presence of a wiggler magnetic field by twisted laser plasma interaction is surveyed. The wiggler magnetic field provides additional momentum required for the phase matching. The Laguerre-Gaussian modes can be used to control the self-focusing and improve the second harmonic generation in laser plasma interaction. The wave equations for the fundamental and the second harmonic fields have been solved in the paraxial approximation. The generation of the second harmonic considering self-focusing is investigated. Also, the dependence of the second harmonic power on the propagation distance for different values of initial fundamental beam intensity,...
Generation of two-soliton and three-soliton molecules in a circular fiber array laser
, Article Laser Physics ; Volume 28, Issue 4 , March , 2018 ; 1054660X (ISSN) ; Rooholamininejad, H ; Bahrampour, A ; Sharif University of Technology
Institute of Physics Publishing
2018
Abstract
In this work, the generation of two-soliton and three-soliton molecules in a circular fiber array laser with an active optical central fiber is studied. Certain fibers of the array are excited by Gaussian and super-Gaussian pulses. The central fiber of the circular fiber laser is a rare-earth doped fiber. A circular fiber array is employed as a saturable absorber in a soliton mode locked fiber laser. Generation of two-soliton and three-soliton molecules are observed in our simulation. Numerical calculation of binding energy shows that the super-Gaussian pulse tends to be more stable, and therefore it would be a proper choice for the generation of soliton molecules in the circular fiber array...
Ping-pong protocol based on the orbital angular momentum of light
, Article Journal of the Optical Society of America B: Optical Physics ; Volume 35, Issue 10 , 2018 , Pages 2348-2355 ; 07403224 (ISSN) ; Tofighi, S ; Bahrampour, A ; Sharif University of Technology
2018
Abstract
Orbital angular momentum (OAM) is one of the photon's degrees of freedom in infinite-dimensional Hilbert space. In this paper, we use this photon property to propose a modified version of the deterministic two-way quantum key distribution protocol, known as ping-pong protocol, based on the OAM of light. The advantage of the protocol is that it does not require Bell measurement for decoding the information being transmitted, which makes the protocol more flexible and feasible for practical applications. We propose an implementation setup and show how the channel capacity of the protocol can be easily increased. The security of the protocol is analyzed and the probability of detecting Eve in a...
Quantum states with equal unlockable correlations and quantum discord
, Article Physical Review A ; Volume 98, Issue 3 , 2018 ; 24699926 (ISSN) ; Mani, A ; Bahrampour, A ; Sharif University of Technology
American Physical Society
2018
Abstract
In the context of quantum locking of classical correlations protocols, the condition for equality of the amount of unlockable correlations and quantum discord of general classical-quantum states is investigated. Based on this condition, the structure of such general states is obtained. This condition imposes two constraints on the structure of general classical-quantum states. After presenting the interpretation of these constraints, their role in quantum locking protocols is discussed. Finally, the derived structure is generalized to quantum-quantum states and the amount of their unlockable correlations is interpreted in terms of their symmetric discord. © 2018 American Physical Society
Optimal exploitation of the resource in remote state preparation
, Article Physical Review A ; Volume 102, Issue 1 , 15 July , 2020 ; Ramezani, M ; Bahrampour, A ; Sharif University of Technology
American Physical Society
2020
Abstract
Transmission efficiency (TE) of remote state preparation (RSP) with a shared quantum state and one bit of classical communication is considered. Following Dakić et al. [Nat. Phys. 8, 666 (2012)10.1038/nphys2377], the encoding and decoding operators of the protocol are restricted to the physically relevant classes of projective measurements and unitary operators, respectively. It is shown that contrary to the previous arguments, the quadratic fidelity as well as the linear fidelity could be a valid figure of merit to quantify the TE of RSP. Then, the TE of the protocol in terms of both linear and quadratic fidelities is evaluated in a fully optimized scenario which includes the maximization...
Two-axis dielectric laser acceleration using two orthogonal laser pulses in a dual-grating base structure
, Article Applied Optics ; Volume 59, Issue 7 , 2020 , Pages 2135-2140 ; Madanipour, K ; Bahrampour, A ; Sharif University of Technology
OSA - The Optical Society
2020
Abstract
In this paper, two-axis dielectric laser acceleration is proposed by introducing a dual-grating base laser accelerator structure excited with two orthogonal propagating ultrashort laser pulses. A 2D periodic structure is designed that provides phase synchronicity between the relativistic particle beam and orthogonal propagating laser pulses. In this way, the particle beam can gain energy from both laser pulses simultaneously. It is numerically demonstrated that utilizing this method increases both the acceleration gradient and acceleration factor up to90%in comparison with dual-grating dielectric laser acceleration. Also, deflecting force elimination, particle beam quality, and bunch...
An inhomogeneous theoretical model for analyzing the temporal response of high concentration erbium-doped fiber laser
, Article Solid State Lasers and Amplifiers III, Strasbourg, 8 April 2008 through 10 April 2008 ; Volume 6998 , 2008 ; 0277786X (ISSN); 9780819471963 (ISBN) ; Karvar, M ; Bahrampour, A ; Sharif University of Technology
2008
Abstract
In this paper the gain dynamics of an erbium-doped fiber laser (EDFL) with an inhomogeneous active medium in the presence of ion pairs is modeled. A two-level model for single ions and a three-level model for ion pairs are employed to write the propagation and rate equations of inhomogeneous laser medium. The governing equations are an uncountable system of partial differential equations (PDEs). By employing the moment method, the system of PDEs is converted to a finite system of ordinary differential equations (ODEs). The Solution of the system of ODEs is used to analyze the output power of a high concentration EDFL. As it expected, theoretical results show that the threshold pumping power...
A new method for solving nonhermitian perturbation theory for the microdisc resonators with phi-periodic refractive index
, Article Proceedings of SPIE- Silicon Photonics and Photonic Integrated Circuits, Strasbourg, 7 April 2008 through 10 April 2008 ; Volume 6996 , 2008 ; 0277786X (ISSN) ; 9780819471949 (ISBN) ; Karvar, M ; Bahrampour, A ; Sharif University of Technology
2008
Abstract
The radiation loss in the whispering gallery resonators causes the eigenvalues of the Maxwell equations with the corresponding boundary conditions complex. The corresponding operators are nonhermitian and for these operators the standard perturbation techniques have some difficulties. In this paper by employing the Floquet theorem a new technique for the φ periodic perturbations is developed. The method is applied to obtain the change of resonance frequencies and losses of φ -perturbed microresonators with cylindrical symmetry. The results are compatible with that are obtained by the Volume Current Method
Dynamic behavior of electric field in the microrings in the presence of Kerr and two-photon absorption
, Article Proceedings of SPIE - The International Society for Optical Engineering, 7 April 2008 through 10 April 2008, Strasbourg ; Volume 6996 , 2008 ; 0277786X (ISSN) ; 9780819471949 (ISBN) ; Karvar, M ; Bahrampour, A ; Sharif University of Technology
2008
Abstract
This paper a simple semi-analytical model for calculation of the time evolution and spatial variation of the electric field in microring resonators in the presence of The Kerr effect and two-photon absorption (TPA) is presented. The theoretical analysis is based on the delayed feedback model, which is well known in microring theory. The model is applied to the Chalcogenide glass and AlGaAs microrings to study the Kerr and TPA effects on the spatial and temporal variation of electric field respectively across the microring. The effects of microring parameters and input signal shapes on the transient behavior are taken into consideration. It is shown that, the results are in good agreement...
An inhomogeneous theory for the analysis of an all-optical gain-stabilized multichannel erbium-doped fiber amplifier in the presence of ion pairs
, Article Optical Fiber Technology ; Volume 14, Issue 1D , 2008 , Pages 54-62 ; 10685200 (ISSN) ; Keyvaninia, S ; Karvar, M ; Sharif University of Technology
Academic Press Inc
2008
Abstract
In this paper the gain dynamics of an all-optical gain-clamped multichannel erbium-doped fiber amplifier (EDFA) with an inhomogeneous active medium in the presence of ion pairs is modeled. A two-level model for single ions and a three-level model for ion pairs are used to drive the propagation and rate equations of inhomogeneous laser medium. The governing equations are an uncountable system of partial differential equations (PDEs). Using the moment method, the system of PDEs is converted to a finite system of ordinary differential equations (ODEs). The solution of the system of ODEs is used to analyze the gain dynamics of all-optical gain-stabilized multi-wavelength heavy doped EDFA....
Periodic structure of different dielectric layers for dielectric laser accelerators
, Article Applied Optics ; Volume 60, Issue 13 , 2021 , Pages 3747-3752 ; 1559128X (ISSN) ; Madanipour, K ; Bahrampour, A ; Sharif University of Technology
The Optical Society
2021
Abstract
In this paper, a periodic structure of different dielectric layers is proposed and investigated for relativistic electron acceleration. The periodic dielectric structure provides an accelerating electric field inside the structure. Results show that the electron beam can experience a strong electric force in one direction during propagation in the structure, leading to the acceleration gradient increasing by more than double in comparison with dual-grating structures. Acceleration gradient enhancement occurs without increasing the electric field much inside the structure; therefore, the maximum achievable acceleration gradient and acceleration factor are increased by more than 100%, reaching...
Continuous quantum clock with high precision and long recurrence time
, Article Physical Review A ; Volume 106, Issue 2 , 2022 ; 24699926 (ISSN) ; Nikaeen, M ; Bahrampour, A ; Sharif University of Technology
American Physical Society
2022
Abstract
Continuous clocks, i.e., clocks that measure time in a continuous manner, are regarded as an essential component of sensing technology. Precision and recurrence time are two basic features of continuous clocks. In this paper, in the framework of quantum estimation theory various models for continuous quantum clocks are proposed, and all tools of quantum estimation theory are employed to seek the characteristics of clocks with high precision and long recurrence time. Then, in a resource-based approach, the performances of the proposed models are compared. It is shown that quantum clocks based on an n two-qubit system not only can have better precision than quantum clocks based on a 2n...
Discrete-modulation measurement-device-independent continuous-variable quantum key distribution with a quantum scissor: exact non-Gaussian calculation
, Article Optics Express ; Volume 30, Issue 7 , 2022 , Pages 11400-11423 ; 10944087 (ISSN) ; Golshani, M ; Bahrampour, A ; Sharif University of Technology
Optica Publishing Group (formerly OSA)
2022
Abstract
In this paper, we study non-Gaussian discrete-modulated measurement-deviceindependent continuous-variable quantum key distribution protocol equipped with a proposed quantum scissor at the receiver side. Our suggested scissor truncates all multiphoton number states with four or more photons and amplifies remaining photon number states in a probabilistic way. Using exact non-Gaussian calculation, we find that quantum scissor meliorates the fidelity and entanglement between two legitimate parties Alice and Bob, at long distances. Therefore, quantum scissor enhances the continuous-variable quantum key distribution protocol range. Examination of the system for different values of the excess noise...
Investigating the Role of Quantum Correlations in Quantum Communication Protocols
, Ph.D. Dissertation Sharif University of Technology ; Bahrampour, Alireza (Supervisor)
Abstract
Communication is nothing but making correlation between sent and received data via mediating particles and in quantum communications these are the quantum carriers that create these correlations. Since quantum carriers can be correlated in ways inaccessible to classical carriers, quantum communication protocols can perform tasks that are classically impossible or less efficient. Therefore, it is expected that in a suitable model, the quantum advantage of any quantum communication protocol can be expressed in terms of the quantum correlations of its carriers. Here we consider two quantum communication protocols, namely remote state preparation (RSP) and quantum locking of classical...
Optical Injection Phase-Locked Loop Application in Continuous-variable Quantum Key Distributions
, Ph.D. Dissertation Sharif University of Technology ; Bahrampour, Alireza (Supervisor)
Abstract
The primary objective of this thesis is to provide solutions addressing some security loopholes in continuous variables quantum key distribution protocols. The coherent detection method is utilized in this particular quantum key distribution scheme, which is a phase-sensitive detection. To measure in the quantum noise limit in the detection part, we need a local optical oscillator, which must possess a high intensity and a consistent phase correlation with the quantum signal. Therefore, reconstructing the emitter’s reference phase in the receiver’s detection system is considered as one of the most critical challenges in these protocols. In order to attain this goal, in the early versions of...