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dc.contributor.advisorOrtaç, Bülent
dc.contributor.authorTeğin, Uğur
dc.date.accessioned2018-05-31T10:45:43Z
dc.date.available2018-05-31T10:45:43Z
dc.date.copyright2018-05
dc.date.issued2018-05
dc.date.submitted2018-05-30
dc.identifier.urihttp://hdl.handle.net/11693/46954
dc.descriptionCataloged from PDF version of article.en_US
dc.descriptionThesis (M.S.): Bilkent University, Department of Materials Science and Nanotechnology, İhsan Doğramacı Bilkent University, 2018.en_US
dc.descriptionIncludes bibliographical references (leaves 53-60)en_US
dc.description.abstractSpatiotemporal pulse propagation in multimode fibers is generally considered as chaotic. Graded-index multimode fibers reduce the complexity due to its equal spacing of the modal wave numbers which also introduces a periodic self-imaging to the propagating beam. This unique phenomenon affects the coupling between the modes thus graded-index multimode fibers are an ideal testbed to study spatiotemporal pulse propagation. In this thesis, various spatiotemporal nonlinear dynamics studied in graded-index multimode fibers to achieve wavelength conversion, supercontinuum generation triggered by cascaded Raman scattering and to develop a novel all-fiber all-normal dispersion mode-locked laser cavity. In normal dispersion regime, spatiotemporal instability of femtosecond pulses discovered numerically and experimentally by exciting a graded-index multimode fiber with a Ti:Sapphire laser capable to generate 200 fs pulses at 800 nm. With 90 THz frequency shift, Stokes and anti-Stokes sidebands are observed. The signature of spatiotemporal instability which allows the sidebands to inherit the spatial distribution of the pump pulse is observed with the spatial characterization of the generated sidebands. Later a high power laser system with adjustable output parameters is developed as a pump source for spatiotemporal nonlinear pulse propagation studies. By employing this source, with MHz pump pulse repetition rate high power octavespanning supercontinuum generation triggered by cascaded Raman scattering is demonstrated. The results obtained with this novel method is the highest average power and repetition supercontinuum source with a standard graded-index multimode fiber in the literature. Additional spatiotemporal wavelength conversion mechanisms, a small gradedindex multimode fiber between single mode fiber segments can be used as a bandpass filter and saturable absorber. These effects are combined in an all- fiber all normal dispersion laser cavity for the first time in the literature. In the demonstrated cavity design, mode-locking is achieved by nonlinear multimodal interference in graded-index multimode fiber segment. All-normal cavity design supports dissipative soliton pulse formation but it requires bandpass filtering. This requirement is satisfied with multimode interference reimaging thus a unique and simple all-fiber cavity design is constructed to generate ultrashort dissipative soliton pulses. The developed oscillator generates 5 ps pulses at 1030 nm with 44 MHz repetition rate. These pulses are externally compressed to 276 fs. All-fiber cavity design ensures stability and 70 dB sideband suppression is measured in radio frequency domain.en_US
dc.description.statementofresponsibilityby Uğur Teğin.en_US
dc.format.extentxiii, 63 leaves : charts (some color) ; 30 cmen_US
dc.language.isoEnglishen_US
dc.rightsinfo:eu-repo/semantics/openAccessen_US
dc.subjectFiber Lasersen_US
dc.subjectGraded-index Multimode bersen_US
dc.subjectYtterbium Doped Bersen_US
dc.subjectNonlinear Ber Opticsen_US
dc.subjectSpatiotemporal Nonlinear Dynamicsen_US
dc.titleSpatiotemporal nonlinear dynamics in graded-index multimode fibersen_US
dc.title.alternativeKademeli-indeks çok modlu fiberlerde uzaysal-zamansal doğrusal olmayan dinamikleren_US
dc.typeThesisen_US
dc.departmentGraduate Program in Materials Science and Nanotechnologyen_US
dc.publisherBilkent Universityen_US
dc.description.degreeM.S.en_US
dc.identifier.itemidB158432


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