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Actualités de l'école

10/05/2017

Doctorate thesis defense of Amira BAILI




Doctorate thesis defense on May 10th 2017 at 15H00 AM ,in Amphi II, Sup’Com.


Entitled :Characterization of optical nonlinearities in photonic structures: Application to sources and optical router

Presented by : Amira BAILII 





Committee


President

Fethi CHOUBANI

Professor, SUP’COM, Tunisia.

 

 

 

Examiners

Adnane ABDELGHANI

Professor, INSAT, Tunisia.

 

Jamel BEL HADJ TAHER

Professor, Professor, ENISo, Tunisia.

 

Member

Mourad MENIF

Professor, SUP’COM, Tunisia.

   

Thesis Director

Rim CHERIF

Associate Professor, ISET’COM, Tunisia.

 

Abstract


Nonlinear effects in optical fibers are improved with the apparition of a new family of waveguides with small core size diameters smaller than the wavelength of the guided light, called “specialty fibers (SpF)”, designed based on photonic crystal fiber (PCF). Recently, SpF made by high nonlinear glasses such as tellurite (TeO) and chalcogenide (As-S/As-Se) allow the observation of nonlinear phenomena at wavelengths not possible in conventional optical fibers. These fibers attract considerable interest owing to their unique properties and wide range of applications which make them subject to intense investigations and research. They have been considered as an inherently excellent candidate for supercontinuum generation and slow light generation for the significant length of nonlinear interaction that can provide. These two phenomena are useful for many applications including WDM sources, fiber sensing, IR spectroscopy, fiber laser, optical tomography coherence, quantum computing and all optical buffering for future all optical routers.


The combination of two or more nonlinear effect conducts to the generation of broad spectrum known as supercontinuum (SC) that can extend from blue to reach infrared wavelength regions for enormous potential applications. The concept of broadband coherent supercontinuum generated in all-normal dispersion (ANDi) fibers in the infrared spectral regions is introduced and investigated in detail. By injecting short femtosecond pulses in only few millimeters fiber length, ultra-broadband, coherent supercontinuum sources extending in the infrared region are generated. The broadening mechanism in ANDi fibers is dominated by self-phase modulation (SPM) and optical wave breaking (OWB) which create new wavelength components with a deterministic phase relation to the injected pulse, resulting in a highly coherent and phase-stable spectrum.


Another attractive aspect of these novel optical fibers, in particular with high nonlinearity, is their use in the investigation of Stimulated Brillouin scattering (SBS). SpF ensure also slow light generation for the development of future all-optical routers. The slow light effect using SBS is investigated. The properties of such a system depend directly on the Brillouin spectrum. Thus, different methods for a Brillouin gain enhancement in order to achieve the maximum time delay are theoretically investigated. The fiber characteristics for slow light such as Brillouin threshold power, Brillouin gain, time delay, time delay slop efficiency, and figure of merit have been calculated. The simulation results indicate a high Brillouin gain and maximum time delay in small core As2Se3 chalcogenide SpF. The results contained in this thesis makes important contributions to the availability and applicability of SpF for mid-infrared, broadband and coherent SC sources and for the optical buffering used in optical routers.


Keywords


Specialty fibers, nonlinear optics, pulse propagation, all-normal dispersion, high nonlinearity, supercontinuum generation, slow light.