The Research On The High Power All-fiber Pulse Ytterbium-doped Fiber Lasers

High power all fiber pulse Ytterbium doped fiber lasers have the characteristics of compact structure,high peak power and good beam quality.Therefore they could be used for various applications,including material processing,spectroscopy,laser radar,remote sensing,and nonlinear frequency conversion.This thesis focus on the key technologies of high power all fiber short pulse Yb-doped fiber laser,and considers to improve the performance of pulse laser by adjusting the parameters of Yb-doped fiber.Q-switching fiber oscillators,mode-locked fiber oscillators and all fiber pulse laser amplifier have been studied in the theory and experiment.Beginning with the theory of Ytterbium doped silica fiber,the features of Ytterbium ions in the silica fiber were illustrated.Basing on the modified chemical vapor deposition technique(MCVD)and solution doping technique,the fabrication of double-cladding Yb-doped fiber were demonstrated.Basing on the home-made YDF,the high power pulse Yb-doped fiber lasers were studied systematically.An all-fiber Master Oscillator Power-Amplifier(MOPA)nanoseconds laser system based on a Q-switching Yb-doped fiber oscillators was demonstrated.Different double-cladding Yb-doped fibers with the core/cladding diameter of 10/130,20/130 and 30/250?m were used in the MOPA nanoseconds laser system,respectively.According to the results in the experiments and numeral simulations,the parameters of Yb-doped fibers were adjusted to improve the performances of pulses laser.The nanoseconds laser with the output power of 200W was obtained in a length of 50/400 double-cladding YDF.The corresponding pulse energy was~3.3mJ.A passively Q-switched Yb-doped all-fiber ring cavity oscillators based on the stimulated Brillouin scattering(SBS)feedback in a length of single mode fiber(SMF)was demonstrated.The Q-switched pulses is generated from the Stokes pulses of SBS and amplified in the YDF.The tens nanoseconds self-Q-switched pulses with high peak power is obtained.The repetition frequency and output power of pulses are tuned by changing the pump power in experiment.A bandpass filter inserted in the laser cavity was used to suppress time jitter of Q-switched pulses.To obtain the pulses laser with the narrower pulse width and higher peak power,the mode-locked Yb-doped fiber lasers were studied in the experiment and theory.An all-normal-dispersion Yb-doped fiber oscillators with mode-locking mechanism based on the nonlinear polarization rotation(NPR)technique was demonstrated.The splitting and trapping of dissipative solitons(DS)could be observed by inserting of a short section of polarization-maintaining fiber(PMF)in cavity configuration as an in-line birefringence fiber filter.Two trapped orthogonal polarization DSs can travel with the same group velocity in the laser cavity.With the DSs trapping,the polarization sidebands are appeared in the spectrum.The trapping of DSs and sideband generation is numerically simulated as well.A mode-locked Yb-doped fiber ring cavity oscillators with a semiconductor saturable absorber mirror(SESAM)was demonstrated.Without the bandpass filter or the fiber grating in laser cavity,the tunable single wavelength and dual-wavelength pulses could still be obtained.It was resulted by the polarization sensitive components that could be equivalent to a birefringence fiber filter in cavity.The evolution of pulses with dual-wavelength in cavity was simulated and analyzed as well.Basing on a SESAM mode-locked Yb-doped fiber line cavity oscillators,an all-fiber MOPA picoseconds laser system was demonstrated.The picoseconds laser with the output power of 100W was obtained in a length of 50/400 double-cladding YDF.The corresponding peak power was~31kW.To suppress the Stimulated Raman scattering(SRS)and to improve the beam quality in the picoseconds laser amplifying process,the cascade long-period Yb-doped fiber gratings were used in the amplifier.Raman peak suppression ratio was nearly 10 dB and the beam quality M~2 maintained at 1.35.