The Research On 2?m Mode-locked Fiber Laser Based On Saturable Absorber Of Molybdenum Selenide

2?m mode-locked fiber lasers have been widely used in biomedical applications,radar sensing and scientific research due to their simple structure and easy miniaturization.In recent years,with the rapid development of two-dimensional materials,molybdenum selenide(MoSe₂)has emerged in many two-dimensional materials due to its high nonlinear refractive index,strong broadband saturation absorption capacity and controllable modulation depth,however,the researches on MoSe₂as a new saturable absorber(SA)in 2?m mode-locked fiber lasers are relatively scarce.In this thesis,a 2?m mode-locked fiber laser based on MoSe₂-SA is designed and realized.The output characteristics of Q-switched,basic,multi-wavelength and multi-pulse mode-locked pulses are obtained,and the energy of the single pulse reached n J level,which extends the excellent SA for the 2?m mode-locked fiber laser.The research contents of this thesis are mainly divided into the following four aspects:1.The background and significance of the 2?m mode-locked fiber laser are analyzed,and the theoretical analysis of the 2?m mode-locked fiber laser based on MoSe₂-SA is carried out,including the gain medium,the pumping mode and the influencing factors of optical pulse transmission.At the same time,the physical model based on MoSe₂-SA is given,and the corresponding distributed Fourier numerical simulation method of the mode-locked fiber laser is discussed.2.A 2?m negative dispersion mode-locked fiber laser based on MoSe₂-SA is designed and realized.Firstly,the best way to prepare MoSe₂-SA is selected from the methods of preparing and transferring MoSe₂,and then the test apparatus and optical devices used in the experiments are analyzed.Finally,the fundamental mode-locked pulse outputs are obtained experimentally,the mode-locked pulse energy is 1.14 n J,which is tens of times higher than the pulse energy of other traditional lasers(0.034 n J).3.Based on the 2?m negative dispersion mode-locked fiber laser,by introducing a dispersion-compensated fiber,a 2?m normal mode-locked fiber laser based on MoSe₂-SA is designed and realized,which is used to study the output characteristics of multi-wavelength mode-locked laser.Under different pump powers,three different multi-wavelength outputs of dual-wavelength,tri-wavelength and four-wavelength are obtained,and the specific output characteristics and stability of the three operating areas are analyzed,and the experiment showed that the three multi-wavelength outputs can run stably.4.Through the study of the 2?m negative positive dispersion mode-locked fiber laser,it is found that because the laser output of MoSe₂-SA is insensitive to polarization,the mode-locked pulses obtained by the laser are all single pulse and the mode-locked types are few,therefore a 2?m mode-locked fiber laser based on MoSe₂-SA is optimized in order to study more diversified mode-locked pulse outputs.A 2?m hybrid mode-locked laser based on MoSe₂-SA and an 8-shape cavity nonlinear amplifying ring mirror is realized by constructing a mode-locked 8-shape cavity structure and inserting MoSe₂-SA into the device,five kinds of mode-locked pulse outputs are obtained through experiments,namely:Q-switched mode-locked pulses,fundamental mode-locked pulses,2-5 pulses,pulse beam and harmonic mode-locking of pulse beam.