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Study Of The Mechanism And Control Of Supercontinuum Generation In Photonic Crystal Fibers

Posted on:2007-04-12Degree:MasterType:Thesis
Country:ChinaCandidate:W HanFull Text:PDF
GTID:2178360185465734Subject:Computer application technology
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Ultrashort pulses propagating in nonlinear media can generate frequency-broadened output beams, called the supercontinuum. Supercontinuum finds numerous applications in the field of telecommunication. Photonic crystal fibers exhibiting high nonlinearity have enabled the generation and control of supercontinuum. Supercontinuum in photonic crystal fibers has become a hot research topic in optical communication. In this thesis, we study the mechanism and control of supercontinuum generation in photonic crystal fibers. The main research results are listed below.The mechanism of supercontinuum generation in photonic crystal fibers is very complicated. Numerical simulation becomes crucial research methods. Based on the nonlinear Schr?dinger equation describing pulse propagation in photonic crystal fibers, we have developed the computer program which can simulate the process of supercontinuum generation. We analyze the mechanism of supercontinuum in photonic crystal fibers in detail. It is shown that the evolution of the spectrum can be divided into three stages. The three stages are initial broadening slowly, dramatic broadening and saturation stage. In the initial formation of supercontinuum self-phase modulation plays a main role while all the higher-order effects play a minor role. With increasing propagating distance, the higher-order effects exert more important influence on supercontinuum. The third-order dispersion leads to spectral asymmetry, while SRS leads to soliton self-frequency shift and the center frequency of soliton is transferred to infrared. SRS leads to more Stokes components of spectrum.The usual method of supercontinuum generation is using the ultrashort pulse as pump pulse. A new method about generating supercontinuum by modulation instability in photonic crystal fibers is proposed. The method can use long pulse to generate supercontinuum. The method is demonstrated numerically, and the mechanism of the new method is analyzed. When quasi-continuous wave is used as pump pulse, it is shown the perturbed Gaussian pulse manifests modulation instability, which leads to the breakup of an initially pulse. Noise spikes are rapidly enhanced by the modulation instability effect. When the propagation distance keeps on increasing, the spectrum side lobes appear and the spectrum extremely broadens and becomes supercontinuum.
Keywords/Search Tags:photonic crystal fiber, supercontinuum, modulation instability, chirp
PDF Full Text Request
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