Research Of Pulse Fiber Laser Based On Novel Two Dimensional Materials

Pulse lasers have widely used in industrial fabrication,laser sensing,laser communications,and medical surgery.Compared with traditional lasers,pulse fiber lasers have the advantages of small size,excellent beam transmission performance,high energy conversion rate,and robustness.They have become the development direction of high-power short-pulse lasers in the future,so the study of pulsed fiber lasers is particularly important.For the purpose above,this paper mainly focuses on the study of short-pulse fiber lasers based on saturable absorbers,especially novel two-dimensional materials.The research work of this paper are listed below:1.We built a mode-locked fiber laser in the 1?m wavelength region based on the nonlinear polarization rotation.Firstly,we built a mode-locked Ytterbium-doped fiber laser with a repetition rate of 72.9 MHz,a pulse width of 1.9 ps,and an output power of 108.7 mW.In order to apply to the saturable absorption measurement system of the two-dimensional materials,we adjusted the laser cavity.In this case,the repetition rate is reduced to 56.9MHz,the pulse width is increased to 3.4 ps,and the maximum output power is up to 180.7mW.The laser pulses is then dechirped to 241 fs using a pair of reflection gratings.2.High energy Q-switched pulses are achieved using transition metal dichalcogenides as saturable absorbers.The MoS₂ and WS₂ used in the experiment are fabricated by microwave-assisted solvothemal method.We prepared these two materials into polymer films.The laser absorption curves of MoS₂ film and WS₂ film show that the modulation depth of MoS₂-PVA is 2.16%and the saturation intensity is 1.276 MW/cm²,the modulation depth of WS₂-PVA is 7.11%,and the saturation intensity is 22.87 MW/cm².Q-switching operation are obtained by inserting MoS₂ and WS₂ films into the all-fiber oscillator respectively.The repetition rate of the Q-switched pulse based on MoS₂-PVA saturable absorber is 152.2 kHz,the single pulse energy is 256 nJ and the pulse width is1.08?s.The Q-switched pulse based on WS₂-PVA has a tunable repetition rete of67.31⁹7.4 kHz,the maximum single pulse energy is 221.7 nJ,and the shortest pulse duration is 0.99?s.3.The Q-switched operation based on transition metal dichalcogenide alloy is achieved in an all fiber Ytterbium-doped fiber laser.We used Mo_0.5W_0.5S₂ as the saturable absorber and compared the Q-switching state of the Mo_0.5W_0.5S₂ film and the Mo_0.5W_0.5S₂ fiber-taper respectively.We measured the saturable absorption of the Mo_0.5W_0.5S₂-PVA film.The modulation depth of the Mo_0.5W_0.5S₂-PVA film is 5.63%,the saturation intensity is 6.82MW/cm²,and Mo_0.5W_0.5S₂ shows a reverse saturable absorption at high incident power.The range of the repetition rate of the Q-switched pulses achieved by the film saturable absorber is 39.44 to 89.09 kHz,the narrowest pulse width of the Q-switched pulse is 1.22?s,and the single pulse energy is 148.8 nJ.Q-switching operation is also obtained using a tapered fiber saturable absorber,the pulse energy is up to 339 nJ and the shortest pulse duration is 1.46?s.