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kerr-nonlinearity
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Enhanced Kerr nonlinearity in a four-level EIT medium
, Article Journal of Nonlinear Optical Physics and Materials ; Volume 19, Issue 3 , 2010 , Pages 503-515 ; 02188635 (ISSN) ; Asadpour, S. H ; Sadighi, R ; Sharif University of Technology
2010
Abstract
The linear and nonlinear response of a four-level EIT system driven by three coherent fields is investigated. It is found that at appropriate atomic parameters, the Kerr nonlinearity can clearly be enhanced. It is also demonstrated that the maximal Kerr nonlinearity enters the EIT window, and the corresponding linear and nonlinear absorption suppress. Moreover, we show that nonlinear absorption and Kerr nonlinearity can also be changed via relative phase between driving fields
Effect of Kerr nonlinearity on the transverse localization of light in 1D array of optical waveguides with off-diagonal disorder
, Article Optics Communications ; Volume 294 , 2013 , Pages 299-304 ; 00304018 (ISSN) ; Golshani, M ; Bahrampour, A. R ; Mahdavi, S. M ; Sharif University of Technology
2013
Abstract
In this paper a simulation of the transverse localization of light in 1D array of optical waveguides in the presence of off-diagonal disorder is presented. Effects of self-focusing and self-defocusing Kerr nonlinearity on the transverse localization of surface and bulk modes of the disordered waveguides array are taken into consideration. The simulation shows that in the off-diagonal disordered array at low nonlinear parameters, the transverse localization of light becomes more than that of the corresponding diagonal disordered array. However by increasing the nonlinear parameters the diagonal disordered array is localized more than the associated off-diagonal disordered array for both...
Enhancement of Kerr nonlinearity at long wavelength in a quantum dot nanostructure
, Article Physica E: Low-Dimensional Systems and Nanostructures ; Volume 43, Issue 10 , August , 2011 , Pages 1759-1762 ; 13869477 (ISSN) ; Sahrai, M ; Sadighi Bonabi, R ; Soltani, A ; Mahrami, H ; Sharif University of Technology
2011
Abstract
The giant Kerr nonlinearity with reduced linear and nonlinear absorption in a four-level quantum dot by employing the tunnel coupling is investigated. It is shown that by enhancement of tunnel coupling value the Kerr nonlinearity increases and at the same time linear and nonlinear absorption reduces at the long wavelength which is very important for communicational applications. Enhanced of Kerr nonlinearity in a double quantum dots is investigated. It is found that the electron tunneling has an essential role to reducing the linear absorption and increasing the Kerr nonlinearity at long wavelength
Light propagation and Localization in Inhomogeneous and Random Optical Waveguide Lattices
, Ph.D. Dissertation Sharif University of Technology ; Mahdavi, Mohammad (Supervisor) ; Bahrampour, Ali Reza (Co-Advisor)
Abstract
Photonic lattices can provide an inexpensive and fine tools to investigate some common phenomena in condensed matter physics, quantum optics, relativistic mechanics,atomic and molecular physics. These phenomena contain Anderson localization,Bloch oscillation, Dynamic localization, coherent and squeezed states, Relativistic Dirac equation, Rabi oscillation, ... .In this thesis, it was investigated three worthy phenomena of them, which at first are introduced in condensed matter physics for electronic systems, in photonic lattices. These phenomena are as follow: Transverse localization of light wave, Bloch oscillation and dynamic localization of light. It was also simulate classically, the...
Effect of long-range correlated disorder on the transverse localization of light in 1D array of optical waveguides
, Article Optics Communications ; Volume 307 , 2013 , Pages 39-45 ; 00304018 (ISSN) ; Mahdavi, S. M ; Bahrampour, A. R ; Golshani, M ; Sharif University of Technology
2013
Abstract
In this paper, the effects of the long-range correlated diagonal disordered optical waveguide arrays in the presence and absence of the positive Kerr nonlinearity are analyzed numerically. The calculated inverse localization length shows that the long-range correlation in a disordered system causes a decrease in the transverse localization in linear optical waveguide arrays. In the presence of positive Kerr nonlinearity, the inverse localization length is increased by increasing the nonlinear parameters in long-range correlated disordered systems in comparison with the uniform distribution disordered systems. This means that the long range correlation causes an enhancement of transverse...
All optical switch based on Fano resonance in metal nanocomposite photonic crystals
, Article Optics Communications ; Volume 284, Issue 8 , 2011 , Pages 2230-2235 ; 00304018 (ISSN) ; Malek Mohammad, M ; Khorasani, S ; Sharif University of Technology
Abstract
We investigate the potential of plasmonic resonance in metal nanocomposite materials for the design of photonic crystal all optical switches by numerical methods. We study the absorption effect of the plasmonic resonance on the Fano resonances of one dimensional photonic crystal slabs covered by a metal nanocomposite layer. It is shown that the absorption reduces the contrast of the Fano resonances. However, for adequate metal nanoparticle concentrations it is possible to achieve both sufficiently sharp Fano resonance and strong Kerr nonlinearity, which provides a suitable condition for the design of high contrast and low threshold switches
Coupler-free surface polariton excitation and propagation with cold four-level atomic medium
, Article Journal of the Optical Society of America B: Optical Physics ; Volume 34, Issue 9 , 2017 , Pages 1787-1795 ; 07403224 (ISSN) ; Sadighi Bonabi, R ; Hang, C ; Sharif University of Technology
Abstract
The possibility of the direct excitation of surface polaritons (SPs) by the free-space laser fields at the interface of negative-index metamaterial (NIMM) layer and a bottom layer of cold double Lambda-type atomic medium is investigated. The giant field enhancement (up to jE∕E0j2 ≈ 4.1), together with suppressed ohmic loss of the NIMM layer in a wide transparency window of a double electromagnetically induced transparency, results in the SPs generation. The excitation efficiency of these SPs can be effectively enhanced by applying the unidirectional atomic motion, modulation of the coupling laser characteristics, and using a probe laser with proper incident angle. Based on the special...
Statistical Characterization of Kerr Nonlinearity in Optical Fiber and Its Corresponding Applications
, M.Sc. Thesis Sharif University of Technology ; Salehi, Javad (Supervisor)
Abstract
Optical fibers with the high amount of nonlinearity, or length such as highly nonlinear fibers (HNLF) and long optical transmission lines could not be simply modeled as linear systems; and, in fact, the propagation of signal through these types of mediums is governed by the nonlinear Schrödinger equation (NLSE). From the statistical point of view, the interaction between signal, noise, and Kerr nonlinearity along the fiber leads to an output random process that is not well studied in the literatures and the exploration in this area may play an important role in solving different practical problems. In order to investigate the aforementioned output random process, this thesis obtains the most...
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...