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Research On Supercontinuum And Raman Laser Based On 2?m Fiber Laser

Posted on:2019-01-05Degree:MasterType:Thesis
Country:ChinaCandidate:K D MoFull Text:PDF
GTID:2348330563453861Subject:Optical Engineering
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2?m pulsed fiber lasers with high pulse energy have attracted tremendous attention due to its wide applications in industrial processing,defense,military,medicine,and so on.This thesis investigates 2?m high energy pulse generation including noise-like pulse,dissipative soliton resonance(DSR),and h-shaped pulse under the frame of passive mode-locking.By pumping a Raman gain fiber with the generated noise-like pulse,pulsed Raman laser with average output power of up to358.9 mW and conversion efficiency up to 92%is obtained at 2167 nm.In addition,supercontinuum generation pumped by noise-like pulses and h-shaped pulses is also studied.The main research contents of the paper are presented as follows.(1)Analyzing and solving the propagation equation of the optical pulse in fiber based on the nonlinear Schr?dinger equation,and build up the model of(nonlinear polarization rotation)NPR mode-locking by combing Jones matrix.Generation and evolution features of noise-like pulse are studied with the numerical model.Through simulating the formation of dissipative soliton resonance,the formation mechanism and feature of the DSR is investigated,and its evolution process is explored as a function of pump power.(2)By using NPR as a mode-locker,stable noise-like pulse with a repetition rate of5.8 MHz is achieved in a passively mode-locked Tm-doped fiber laser with a cavity length of 30 m and anomalous net cavity dispersion of-2.4 ps~2.The highest pulse energy of 75.2 nJ is obtained under the maximum pump power of 5.6 W,where its pulse duration and center wavelength are 1.74 ns and 1971.8 nm,respectively.The high signal-noise ratio of 48.6 dB indicates its good stability.When the cavity length extends to 240 m,stable DSR featured by a square waveform is obtained under repetition rate of863 kHz.Like simulation,pulse duration of the DSR continuously increases as the pump strength increases,while the pulse top always maintains flatness feature with fixed amplitude.Highest pulse energy of 58 nJ of the DSR with large pulse duration of12.89 ns is obtained at the maximum pumping power 5.6 W.Furthermore,if the cavity length decreases to 200 m,an h-shape pulse is obtained with repetition rate of 980 kHz.This pulse exhibits part of characteristics of dissipative soliton resonance pulse and shows wider pulse duration than the dissipative soliton resonance pulse at the same pump power.The largest pulse duration of this type pulse is 24 ns,where the corresponding pulse energy of 183 nJ.(3)By pumping a Ge-doped silica fiber with an amplified noise-like pulse with a peak power of 63.4 W,supercontinuum with wavelength covering range of 500 nm is obtained.Supercontinuum with the same wavelength covering range is also obtained with h-shape pulse with peak power of 160 W.(4)By pumping a 25 m Ge-doped fiber with amplified noise-like pulse with a low peak power of 79.9 W,first-order pulsed Raman laser with center wavelength of 2167nm is obtained.the highest optical to optical conversion efficiency from noise-like pulse to Raman pulse is up to 92%.Under the maximum conversion efficiency,the Raman pulse energy and pulse duration are 145.9 nJ and 2.1 ns,respectively.To our best knowledge,this is the first demonstration of Raman fiber laser with such high conversion efficiency and good stability.
Keywords/Search Tags:Noise-like pulse, Dissipative soliton resonance, H-shaped pulse, Raman laser, supercontinuum
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