Multi-soliton Dynamics Study Of Passively Mode-locked Erbium-doped Fiber Lasers

The 1.5 ?m band erbium-doped fiber laser has become a hot research direction in recent decades because of its tunable bandwidth,compact structure,high output power,high stability and relatively low cost.Its application fields include medicine,spectroscopy,laser ranging and lidar detection.Fiber laser can output different forms of soliton pulses.When the pump power reaches a certain value,the intracavity pulse energy does not continue to increase,but splits into several multiple soliton pulses,which have the same physical properties as the pulse energy and pulse width.The multi-soliton pulse is not only used in time division multiplexing system,laser communication,but also involved in laser ranging,optical fiber sensing and other fields.At the same time,it provides a development direction for high-power pulsed fiber laser.In this paper,the soliton dynamics of an erbium-doped fiber laser is experimentally studied and simulated based on the nonlinear polarization rotational mode-locking technique.The main contents of this paper are as follows:An erbium-doped fiber laser is constructed on an optical platform based on nonlinear polarization rotation mode-locking technology.By carefully adjusting the angle of the polarization controller,the multi-soliton pulses with arbitrary soliton spacing are obtained.In the experiment,the effects of pump power and polarization state on the multi-soliton pulse are explored,and the quasi-quantization law of the spacing distribution of soliton is found.In order to continue to explore whether there are other factors influence the soliton interval numerical regularity of the change,the pulses are observed by changing the parameters of the laser cavity,such as the length of single-mode optical fiber,the length of gain optical fiber,the position of single-mode optical fiber,etc.In addition,the dynamic behavior of such multi-soliton pulses is summarized by comparing the characteristics of the variation of the multi-soliton pulse interval in erbium,thulium,and ytterbium-doped optical lasers.Based on the principle of nonlinear polarization rotation mode locking,the physical transmission model of passive mode-locked erbium-doped fiber laser is constructed by pulse tracking method in the simulation software,and the classical single soliton pulse and multi-soliton pulse are obtained by adjusting the parameters in the program.Then the dynamic behavior of multiple soliton pulses is studied by changing the pump power and the control parameters of the model.Multiple soliton pulses begin to radiate and become stable as the number of operating cycles increases.The spacing of multiple solitons is controlled by changing the polarization state to produce dispersion wave,and the physical mechanism of the change of the spacing of solitons is verified.