High Power Nanosecond Pulse Yb-doped Fiber Laser

Nanosecond pulse fiber lasers are widely used in laser processing, optical timedomain reflectometer (OTDR), and the passively Q-switched has many advantages oflow-cost, compact, easy to integrate and so on.We have in-depth researched with thesaturable absorber passively Q-switched ytterbium-doped fiber laser in this paper,with the existing conditions of our laboratory, we have made the following works:(1) We achieved a passively Q-switched nanosecond pulse ytterbium-doped fiberlaser. From the rate equations of the fiber laser and the passively Q-switched saturableabsorber respectively, through both the theoretical calculations and the simulations,we have discussed the impact on the pulse width and output power from the mainparameters of the fiber laser: pump power、the length of laser cavity and thereflectivity output mirror, thereby optimized the design of the cavity shape.(2) In the Cr: YAG saturable absorber passively Q-switched cladding-pumpedytterbium-doped fiber laser, there are two cavity shapes of ring cavity and linear cavity.The ring structure with stable laser output of the pulse width is257ns, the repetitionfrequency is19.1kHz, the center wavelength is1075nm.The linear structure withstable laser output of the pulse width is156ns and repetition rate is30.3kHz, thecenter wavelength is1063.9nm, using Cr: YAG crystal passively Q-switched pulsesequences are stable, the amplitude jitter and time jitter are less than5%(rms).Inaddition, compared the Q-switched fiber laser with different focal length mirrors in theexternal cavity, as well as different thickness, different initial transmission of Cr: YAGcrystal.(3) In order to compare the difference between cladding-pumped andcore-pumped, we also used the Cr: YAG crystal in a core-pumped passivelyQ-switched fiber laser.A ultrashort cavity of70cm was created in a linear structure,when the maximum pump power was513.92mW, we got the narrowest pulse widthwas24ns, repetition frequency was33kHz, center wavelength was1064.1884nm withstable pulse tail, the amplitude jitter and timing jitter were less than5%(rms).(4) Because there are all needs of high-power nanosecond pulsed fiber laser inthe fields of laser processing, military and so on. While the core-pumped fiber laseroutput power is low, so we amplificated the laser seed source output, ultimately, weobtained a average output power was7.174W, repetition frequency was27.8kHz, the laser pulse output of pulse width was123ns, this kind of high power fiber lasers arewidely used in many areas.(5)Due to the unique structure and properties of graphene since graphene wasdiscovered in2004, it have been widely used in fiber lasers as a mode-locked orQ-switched component.In graphene saturable absorber passively Q-switchedcladding-pumped ytterbium-doped fiber laser, we also created two cavities of a ringcavity and a linear cavity, they all have the advantages of compact and all fiberstructure.In the ring cavity, while the pump power was488.1mW, the pulse width was1μs, the repetition frequency was11.72kHz, the center wavelength was1068.5nm.Inthe linear cavity we have got one hundred seconds of the pulse width.When the pumppower was361.6mW, the narrowest pulse width was760ns and repetition frequencywas40.1kHz, the center wavelength was1064.488nm.This subject of passively Q-switched effectively inhibited the self-pulse and fibernonlinear effects. There were no phenomenon of self-mode-locking, the narrowestpulse width was24ns, the pulse sequence is very stable and has advantages ofcompact structure, small size,low cost, easy to operate and so on, so it has the realityvalue of industrial.