The Study Of Fiber Lasers Based On New Saturable Absorbers

Due to the advantages of high pulse energy and high peak power,short pulse fiber laser has been rapidly developed both in researched and applications such as laser micromachining,minimally invasive surgery,terahertz wave generation,optical imaging and supercontinuum generation and so on.On the other hand,in recent years,various new two-dimensional materials such as Graphene,Silicene,Antimonene and Transition Metal Sulfides?MoS₂,WS₂,ZrS₂?have been widely investigated in all fiber lasers owing to their excellent light modulation characteristics such as fast response time,small optical loss,strong nonlinear effect and wide absorption wavelength range as well as their low cost and easy preparation.In this work,pulse fiber lasers based on three different new two-dimensional saturable absorbers?SAs?have been studied.Firstly,WS₂,ZrS₂ and Silicene nanosheets and the corresponding SAs are prepared seperately.Then,the short pulse fiber lasers are implemented using the three kinds of prepared SAs.The experimental results are recorded,analyzed and discussed in detail.1.Short pulse fiber laser based on WS₂-SA is studied both in ytterbium?Yb?-doped fiber?YDF?laser and erbium?Er?-doped fiber?EDF?.?1?A Q-switched 1.5?m EDF laser based on the saturable absorption characteristics of WS₂ is demonstrated.The repetition rate varies from 41.6 kHz to 66.6 kHz along with the increasing pump power.The obtained narrowest pulse width is 1.4?s and the maximum single pulse energy is 298.6 nJ.?2?A mode-locked 1.5?m EDF fiber laser based on WS₂-SA is studied in detail.The fundamental repetition rate of the mode-locked pulse is 1.698 MHz.By adjusting the polarization controller,which is due to optimize the birefringence of the resonant cavity,its high repetition rate mode-locked including second harmonic mode-locking?FWHM=3.39 MHz?and 214 harmonic mode-locking?FWHM=363.3 MHz?is realized experimentally.?3?A Q-switched 1.12?m YDF laser based on the saturable absorption characteristics of WS₂ is demonstrated for the first time.The pulse repetition rate increases from 35.6 kHz to 61.0kHz along with the increasing pump power,and the obtained narrowest pulse width is 5.29?s.2.A Q-switched EDF laser by ZrS₂-SA is demonstrated.The repetition rate varies from40.65 kHz to 86.2 kHz when the pump power is increased from 55 mW to 345 mW.The maximum energy is 34.7 nJ for each pulse.The obtained shortest pulse width is 1.49?s,which is the narrowest pulse width reported in the Q-switched fiber lasers by ZrS₂-SA so far.3.A Q-switched EDF laser by Silicene-SA is demonstrated.The oscillating center wavelength of the laser is 1567 nm.When the pump power is 165 mW,the narrowest pulse width is 2.32?s and the maximum output power is 5.46 mW.The stable operation proves that Silicene nanosheets have good saturable absorption properties.4.The Bright-Dark soliton pairs generated by nonlinear polarization effect in EDF laser are experimentally studied.The pulses of bright and dark solitons are obtained when the pump power reaches up to 220 mW.The amplitude of soliton pair is inversely proportional to the intensity of incident pump power.Besides,the shape of the solitons is quite sensitive to the change of polarization state of the system.