Research On Multi-state Soliton Fiber Lasers And The Complex Soliton Transient Dynamics

Serving as an excellent seed source for ultra-short pulses with high peak power and wide spectrum,the ultra-fast fiber lasers play an indispensable role in basic scientific research and industrial applications.On the one hand,the good coherence properties,high repetition rate,wide band wide tunable range and other technical features have also brought a breakthrough in optical fiber communication,sensing,storage,and other fields.On the other hand,it is a good experimental platform for the most rapid and super nonlinear optical physics exploration,and embodies the important scientific research value in the field of laser physics research.Further,it deepens the understanding of the nature of laser physics for the majority of researchers.In this thesis,oriented to the exploration of laser physics and application demand of ultrafast fiber laser technology,we systematically study the dispersion management based multi-state pulses fiber laser and the vector-scale multi-state pulses fiber laser.Moreover,the transient evolution of two kinds of soliton complexes,including the soliton molecules and group velocity locking vector pulses,is also revealed based on all-fiber passive mode-locked fiber lasers with the help of time-stretch dispersive Fourier transform technique.The main results of this paper are as follows:(1)Dispersion managed multi-state pulses fiber laser: It is demonstrated that,with fine laser dispersion parameter control,the stretch pulses/conventional solitons and stretch pulses/dissipative solitons can be generated in the fiber lasers located in near-zero negative dispersion regime and near-zero positive dispersion regime,separately;a bidirectionally mode-locked fiber laser is constructed for emitting conventional solitons and dissipative solitons,which exist in different dispersion regimes;finally,a multi-port fiber laser is designed to analyze the pulse evolution dynamics during the pulse reforming process,which provides a certain guiding significance for the study of multi-state pulses fiber laser,and provides important experimental data for the study of pulse evolution dynamics in the laser.(2)Scalar-vector multi-state pulses fiber laser: Using two circulators to construct two branches of opposite direction transmission in the laser,the local strong birefringence characteristic of a polarization-preserving fiber are applied to introduce the different polarization evolution mechanisms in the two directions to realize the bidirectional output of scalar and vector pulses of fiber laser.Further,the spectral modulation of vector solitons is studied by using the polarization de-multiplexing system outside the laser cavity.The corresponding relationship between relative phase and intensity difference between two orthogonal polarization components and spectral pattern is quantitatively analyzed.In addition,the existence of vector-scalar noise-like multi-state pulses is confirmed in the experiment,whose spectra and autocorrelation trace features similar to vector-scalar pulses.This result enriches the research scope of scalar-vector multi-state pulses,and vector noise-like pulses,as a high-energy pulse cluster,also have great application prospects.(3)Transient dynamics of bound-state pulses: A research platform for ultrafast fiber laser dynamics based on a 45°tilt grating is set up to study the interaction and coexistence mechanism of soliton monomer/soliton molecules on nanosecond time scale combined with time stretching-dispersive Fourier transform.The ultrafast evolution process of inner soliton molecules in bound states is explored on picosecond time scale.The internal dynamics of soliton molecules are studied in the multi-pulse mode-locking operation,where three kinds of transient evolution characteristics of soliton molecules,namely the periodic phase evolution of soliton molecules,the phase divergence evolution of soliton molecules and the pulsation of soliton molecular spacing,are observed.The results are helpful for expanding the potential applications of ultrashort pulses in high-order coding modulation and all-optical storage.(4)Transient dynamics of vector pulses: The passive mode-locking mechanism based on multi-modefiber with gradient refractive index distribution is studied,and the experimental platform of vector passive mode-locking fiber laser is constructed.By adjusting the dispersion parameters in the cavity reasonably,the generation of group velocity locking vector pulses is realized in the anomalous dispersion domain and the normal dispersion domain respectively;Based on the time-stretch dispersive Fourier transform,the polarization kinetic characteristics are further explored.Besides,the pulsating mode of velocity-locked vector dissipative solitons is studied in vector soliton fiber laser.It is of great value to explore the transient polarization dynamics process and optimize the stability of fiber laser.It can provide the research foundation for exploring new phenomena and application of laser physics.