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Characteristics Of Solitons In Passively Mode-locked Fiber Laser Using A SESAM

Posted on:2014-04-04Degree:MasterType:Thesis
Country:ChinaCandidate:Z Z DongFull Text:PDF
GTID:2268330401965164Subject:Optical Engineering
Abstract/Summary:PDF Full Text Request
Optical solitons have attracted considerable interest due to their excellent physicalproperties and great application prospects in optical communications, signal processingand other fields. A passively mode-locked fiber laser employing a semiconductorsaturable absorber mirror (SESAM) in the cavity can generate stable femtosecondoptical soliton pulses. The laser has the advantages of self-starting, simple and compactstructure, low pump threshold, good stability and all-fiber structure. In recent years,femtosecond pulsed source has become one of the hotspots in the research field ofultrafast optics. The current dissertation presents results of a series of theoretical,experimental and numerical investigations on the features of optical solitons formed in apassively mode-locked fiber laser based on a SESAM.Firstly, the saturable absorption property of SESAM was briefly analyzed. Thefiber dispersion and nonlinear effects on the pulse propagation in optical fibers wereintroduced. The formation mechanism of optical solitons was discussed. The nonlinearSchrodinger equation (NLSE) governing the nonlinear pulse propagation in single-modefibers, the Ginzburg-Landau equation describing optical pulse propagation in Er-dopedfibers, and the coupled Ginzburg-Landau equations describing optical pulse propagationin birefringence fibers were derived.Secondly, a passively mode-locked fiber laser based on a SESAM was constructed.Experimentally, soliton pulses with pulse width of750fs, repetition rate of9.6MHzand center wavelength of1561nm were obtained. By employing an external polarizerafter the output of the laser, two orthogonal polarization components of vector solitonswere obtained and studied. Polarization-locked vector solitons (PLVS), group velocitylocked vector solitons (GVLVS) and period-doubling of vector solitons were achieved.In addition, the phenomena of harmonic mode locking, dual-wavelength mode lockingand multi-wavelength CW operation of the laser were observed.Thirdly, the pulse tracing method was used to numerically simulate thecharacteristics of vector solitons based on the coupled Ginzburg-Landau equations.Polarization-locked vector solitons (PLVS) and group velocity locked vector solitons (GVLVS) were obtained in anomalous dispersion region by varying the cavitybirefringence, which were consistent with the experimental results. When the net-cavitydispersion was set to be positive by inserting dispersion compensating fiber (DCF) inthe cavity, dissipative solitons, exhibiting sharp leading and trailing edges, wereobtained numerically. Meanwhile, two orthogonal polarization components of vectordissipative solitons were also numerically simulated.
Keywords/Search Tags:mode-locking, Er-doped fiber laser, SESAM, optical soliton, vector soliton
PDF Full Text Request
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