Pulse Output Characteristics Of Fiber Laser Based On Graphene Oxide Nanocomposite

Ultrafast fiber lasers have received extensive attention in the fields of biomedicine,fiber sensing,and optical information processing.As an ultrafast laser,passively mode-locked fiber laser（PMLFL）can realize high-quality pulse output with narrow pulse width and high power.Among them,PMLFL based on saturable absorbers of two-dimensional materials have been widely studied due to their advantages of simple fabrication,compact structure,and low price.In this thesis,we mainly focus on the pulse output characteristics of passive mode-locked fiber laser based on graphene-oxide（GO）nanocomposites.The main contents are as follows:1.We investigated the GO-based PMLFL,resulting in the generation of a conventional mode-locked pulse.By adjusting the pump power and polarization controller,harmonic dual-wavelength pulse output.Moreover,the phenomenon of multi-soliton beams with wavelengths in the range of 1561.4 nm to1563.2 nm was realized,which has great application prospects in beam encryption and information transmission.2.We examined the saturable absorption properties of antimony selenide（Sb₂Se₃）/GO nanocomposites.The measured modulation depth and saturation light intensity were 4.78%and 9.86MW/cm²,respectively.We applied Sb₂Se₃/GO to PMLFL for the first time and achieved a stable mode-locked pulse output.Compared with GO as a saturable absorber,better pulse output characteristics were obtained.This research has contributed to the application of Sb₂Se₃ nanomaterials for ultrafast photonics research to some extent.3.Additionally,we delved into the saturable absorption properties of vanadium selenide（VSe₂）/GO nanocomposites,achieving a conventional mode-locked pulse output and the fascinating phenomenon of soliton molecules based on VSe₂/GO nanocomposites.The measured modulation depth and saturation light intensity were 14.3%and 0.93 MW/cm²,respectively.The experimental results demonstrated that the VSe₂/GO nanocomposite is a feasible saturable absorber device and provides a low-cost and efficient solution.4.We have performed numerical simulations to study the dynamics of conventional soliton and soliton molecular pulse generation in a fiber laser.It was found that as the pump power increases,a single pulse undergoes a soliton splitting phenomenon.In this case,the soliton molecule needs to undergo several non-linear modulation processes to form a steady state,demonstrates a novel dynamic phenomenon,and the results of the simulation process match the experimental results.The numerical simulation method allows for a more intuitive study of the transient dynamics of multiple pulses,which can be of guidance in improving the performance parameters of the laser.