Passively Mode-locked Fiber Laser And Pulse Characteristics

Passively mode-locked fiber lasers have been used in many fields such as optical communication and optical sensing,precision manufacturing,biological microscopic imaging,military defense,aerospace and so on,due to their narrow pulse width,high peak power,simple structure and low cost.With the development of research,the new mode-locking mechanism and various pulse characteristics of passively mode-locked fiber lasers have attracted extensive attention.This paper mainly conducts theoretical simulation and experimental research on passively mode-locked fiber laser and its pulse characteristics.The generation of multiple mode-locked pulse patterns are theoretically simulated,and the influence of cavity parameters on the pulse pattern are analyzed.Experimentally,2H-Mo Te₂,graphene oxide(GO),and nonlinear polarization rotation(NPR)are built under normal and anomalous dispersion conditions.Various pulse patterns have been obtained,and the output characteristics have been analyzed.The main content of this article includes:1.Introduction.The research background and significance of passively mode-locked fiber lasers are introduced,and the corresponding mode-locked mechanism,pulse pattern and Time-Stretch Dispersion Fourier Transform(DFT)technology are described in detail.2.The establishment of the theoretical model of passively mode-locked fiber laser.The model of pulse transmission in the fiber is introduced,and the nonlinear Schr?dinger equation and the Ginzburg-Landau equation including the gain term are given.The theoretical model of three types of saturable absorber(SA)is dicussed,the transmittance curves of SAs are given,and the influence of different parameters on the transmittance curve is analyzed.3.Numerical simulation of passively mode-locked fiber lasers.The normal dispersion real SA and anomalous dispersion NPR mode-locked fiber laser models are established.Seven different pulse patterns are obtained by simulation,include traditional soliton,dissipative soliton(DS),dissipative soliton resonance(DSR),multi-pulses,noise-like pulse(NLP),breathing soliton and soliton explosion state.The effects of different parameters on the output pulse are discussed,and the map of pulse pattern in normal dispersion is given.The Mamyshev oscillator is simulated,and the pulse evolution in the cavity and the influence of the filter on the pulse state are discussed.4.Experimental research of anomalous dispersion Erbium-doped mode-locked fiber laser.Mode-locking experiment used 2H-Mo Te₂ as SA,which obtains the noise-like pulse output.Mode-locking experiment used GO as SA,soliton and multi-pulses is obtained in a short cavity,and the spectral evolution of soliton is measured by DFT.Then the soliton rain state is observed in a long cavity.In the NPR mode-locking experiment,the traditional soliton,multi-pulse and breathing soliton are obtained in short cavity,the spectral and time domain evolution processes are observed by DFT.DSR pulse output is obtained in a long cavity.5.Experimental research of normal dispersion Ytterbium-doped mode-locked fiber laser.Q-switching experiment based on 2H-Mo Te₂ SA,the range of pulse repetition frequency is 58.7 k Hz-1.54 MHz.In the experiment of all polarization maintaining"9"shaped fiber laser,square wave pulse with adjustable pulse width and peak value is achieved by the angle fusion spliced and stretched fiber.NPR mode-locked fiber laser filtering and main oscillation power amplification(MOPA)experiment is carried out,when the seed source output is DS pulse,the pulse characteristics is studied,and the process of mode-locking establishment and pulse characteristics are studied,the 1024 nm mode-locked pulse is obtained.