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Research On Linear Cavity Mode-locked Yb-doped Fiber Laser

Posted on:2017-04-05Degree:MasterType:Thesis
Country:ChinaCandidate:Y ShenFull Text:PDF
GTID:2308330509456867Subject:Optics
Abstract/Summary:PDF Full Text Request
Compared with the ring cavity, the resonance cavity configuration of the linear cavity passively mode-locked fiber laser was built without an intra-cavity filter and optical isolator, which makes this system simple, low cost and easy integration, etc. Recently, the research on linear cavity mode-locked fiber laser based on saturable absorber(single-walled carbon nanotubes, graphene, topological insulator, black phosphorus and semiconductor absorption mirror SESAM, etc), nonlinear effects of optical fiber(nonlinear optical loop mirror NOLM, nonlinear polarization rotation NPR, nonlinear amplifying loop mirror, etc) and self-mode-locking have been reported. SESAM is the most maturely developed and widely used technology, which can generate the pulses from nanoseconds to femtoseconds. However, SESAM has some drawbacks such as complex and expensive. Linear cavity mode-locked fiber lasers based on saturable absorber(SA) have been reported rarely, and most of that incorporating SA into the laser cavity by the direct interaction between the light beam and SA. These schemes are susceptible to be affected by the thermal damage, which limits the output energy of the pulse. The fabrication of NOLM is more simple by connecting two output terminals of a 2x2 optical coupler. Self-mode-locked fiber laser can obtain pulse laser without any specific mode-locker in the resonance cavity.In this paper,we described a linear cavity Yb-doped fiber laser with a NOLM and self-mode-locked Yb-doped fiber laser, respectively. Theoretical and experimental analyses of the output pulse characteristics have been carried out. The main works of this paper as follows:1. Main types and physical mechanisms of linear cavity passively mode-locked fiber laser were presented and analyzed. We also summarized the research status of the various kinds of lasers in recent years.2. Gain features of fiber laser were analyzed based on the rate equation of Ybdoped fiber. Then the model of ultra-short pulse transmission in a linear cavity fiber laser was developed based on the generalized nonlinear schr?dinger equation, and the effects of self-phase modulation, group velocity dispersion and third-order dispersion on the evolution of the pulses in fibers have been analyzed. Under the conditions of single-mode-fiber with different lengths, Yb-doped fiber with different lengths and different absorption coefficient, the variation trends of pulse characteristics propagating in optical fibers have been simulated and analyzed in the frequency domain and time domain.3. We have investigated experimentally the linear cavity Yb-doped fiber laser mode-locked with a NOLM. The output performance of the laser has been analyzed when the NOLM was fabricated with different length fibers. We have obtained the Qswitching, Q-switched mode-locking and mode-locking, respectively. The generating threshold, intensity and width of the pulse have also been analyzed.4. The self-mode-locking characteristics of Yb-doped single-clad fiber laser with a linear cavity and Yb-doped double-clad fiber laser with a ring cavity have been investigated, respectively, which were designed without any intra-cavity polarizing component. By changing the length of the resonance cavity, the phenomenons of selfQ-switching, self-Q-switched mode-locking and self-mode-locking were observed in the linear cavity Yb-doped single-clad fiber laser, respectively. We have also obtained the bright pulse, bright-dark pulse and dark pulse in the ring cavity self-mode-locked Yb-doped double-clad fiber laser by adjusting the pump power, and the self-pulsation and the transient phenomenon in continuous wave were further analyzed and discussed.
Keywords/Search Tags:mode-locked fiber laser, NOLM, self-mode-locking, Yb-doped fiber, dark pulse
PDF Full Text Request
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