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Study On Graphene Mode-locked Erbium Doped Fiber Pulse Laser

Posted on:2016-09-15Degree:MasterType:Thesis
Country:ChinaCandidate:R L WangFull Text:PDF
GTID:2348330503986983Subject:Physical Electronics
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Optical fiber communication is developing rapidly in recent decades, which has a strong influence in every aspect of daily life. The research about fiber lasers have emerged in great numbers and have achieved fruitful results. There are two reasons. One is that laser is widely used in optical communication, the other is that optical fiber has the advantages of small size and low loss. But with the development of science and technology, the traditional fiber laser can not meet growing needs of society because of limits of its pulse width. Therefore, studying on ultrafast laser has become popular. At the same time, the emergence of graphene provides a new type of saturable absorption material for mode-locked laser, whose saturable absorption characteristics can narrow the optical pulse, even to the femtosecond. In this context, experimentation study and simulation analysis have been done on output characteristics about graphene modelocked fiber laser. Three parts are included in this paper:The graphene has been transferred to the fiber optical connector by using the improved pulse laser deposition method. The method of improved pulse laser deposition needed several steps. First we immersed the fiber optical connector into the graphene solution and then connected the other end of the optical fiber connector to the pump laser through the coupler. The output of power meter jumped suddenly after a few minutes. At this time, graphene has been attached to the end of the optical fiber connector and the deposit has been completed. So we could insert the grapheme into the ring cavity. Stable optical pulses appeared on the oscilloscope when we appropriately adjusted the polarization controller. We have obtained the pulse width of the output of 520 ns, a fundamental repetition rate of 1.92 MHz and the RF spectrum of 75 dB. When Kelly sideband appeared, the wavelength of the output centered at 1557.3 nm. The fiber laser exhibited the maximum output power of 3.2 mW.In the part of simulation, an equation concerning on the experimental has been established according to the Maxwell equation, and the output characteristic of the graphene mode-locked fiber laser has been simulated by this equation. The derivation of this equation mainly included several steps. First, we transform the Maxwell equation into the wave equation, then we could get Fourier transform of the wave equation. For simplicity, we only needed longitudinal mode of the equation. We just needed second order Taylor series, because the higher than the third order effect could be neglected. The equation we needed was obtained when the inversed Fourier transform has been done. In the process of deriving the equation, the four simplifying conditions make equation more concise and more easier to solve. The four conclusions have been drawn from the simulation results, and the four conclusions have validated the output characteristic in both the time domain and frequency domain.Finally, in the time domain, the experimental and simulation results have shown that the output pulse wss a soliton pulse. in the frequency domain, the Kelly sideband was analyzed. The experimental results have achieved the expected results, and the simulation has proved the correctness of the experiment.
Keywords/Search Tags:fiber laser, graphene, saturable absorber, passive mode locking, split step Fourier transform
PDF Full Text Request
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