All-fiber Polarization Maintaining Ultrafast Laser System And Its High-power Supercontinuum Generation

Supercontinuum(SC)source exhibits characteristics of broad spectrum,high brightness high coherence,etc.,which has potential applications in spectroscopy,biomedical imaging,industrial inspection,metrology,optical fiber communications,optical coherence tomography,military,and other basic research fields.Whereas,master oscillator power(MOPA)system is one of the main approaches to realize high power laser emission.It has the characteristics of simple and compact structure,easy integration,high beam quality and high conversion efficiency.As for ultrafast pulse seeded MOPA system,considerable nonlinear effects can arise in the amplifier,and SC can even be formed.In this thesis,combining both merits with SC and MOPA system,the generation of high-power broadband SC is realized in an all polarization-maintaining(PM)EDF MOPA.The main results are as follows.1.Experimental study of all-fiber polarization maintaining fiber oscillator based on semiconductor saturable absorbing mirror(SESAM).Mode-locked pulse with a center wavelength of 1563.7nm,3-dB bandwidth of 12.56nm,repetition frequency of 19.76MHz,and average output power of 1.2mW is obtained through experimental optimizations.Signal to noise(SNR)of radio frequency(RF)at the fundamental repetition rate reaches 75.62dB.By using an autocorrelator,the measured pulse width with Sech2-fit is 209 fs,after amplifying the average power to 21 mW.2.Experimental study on linear cavity ytterbium-doped fiber oscillator based on SESAM.Mode-locked pulse with center wavelength of 1064.17mn,3-dB bandwidth is of 0.07nm,repetition frequency of 45.95MHz,and output power is 0.4mW is realized.3.Research on characteristics of cascaded power amplification characteristics of the all PM EDF oscillator.Through direct cascaded power amplification,1.11W average power is realized with no significant nonlinear effect.In order to enhance the power level,a piece of normal dispersion fiber is added in the cascaded amplifiers,where the emitted laser power is further improved to 1.63W.4.Research on high power supercontinuum generation in cascaded nonlinear fiber amplifier.Employing cascaded nonlinear amplifications of stretched soliton,SC is generation with an average power-11.51W,spectrum spanning across-750nm(from 1450nm to 2200nm),and 11dB bandwidth of?600nm.Experimental measurement shows that the polarization extinction ration(PER)of the finally emitted SC reached>18dB.This is the highest SC power directly produced in a PM EDF system.