The Study Of SESAM-based All-polarization-maintaining Yb³⁺-doped Ultrashort Pulse Fiber Laser

Ultrashort-pulse fiber lasers show great potentials in medical and industrial processing due to the high beam quality and conversion efficiency.In recent years,with the continuous deepening of research in this field,researchers have gradually improved the stability of ultrashort-pulse fiber lasers.The passive mode-locked laser of using the structure of all polarization-maintain fiber,which has important applications in many fields,especially in optical communication due to environment stable and polarization characteristics.In this paper,we use the structure of all polarization-maintain fiber and the SESAM as the mode locker,and we can obtain the pulse energy tunable fiber laser by adjusting the distance between the focuser and the SESAM.Moreover,we can obtain the peak power to the 5 kW in all polarization-maintain fiber based on the pulse energy tunable which can be regarded as the seed laser based on the MOPA technique.At the same time,the bound states of solitons and harmonic solitons mode locking are obtained by introducing mechanical perturbation and increasing the length of cavity length in the laser,respectively.The specific research work and the experiment results are as follows:First of all,we studied the passive mode-locked fiber all polarization-maintain doped Yb3+ fiber laser based on SESAM and distribution and evolution of pulse intensity in fiber lasers was theoretically simulated.Furthermore,the environment stable pulse energy tunable fiber mode locked fiber laser was demonstrated in experiment,the single pulse energy was varied from 0.591 nJ to 0.988 nJ by adjusting the distance between the focuser and the SESAM.The average output power at 15 mW measured over 10h showed an excellent stability of this design.Then,the soliton of different pulse energy generated by the tunable laser was amplified based on the MOPA technique,which can obtain a different pulse.Where the maximum average power of the seed laser was amplified which resulted in peak power of almost 5 kW pulse output,and measured over 24h showed an excellent stability of this design.Finally,when we introduced the mechanical perturbations in all polarization-maintaining fiber laser,and obtained the bound states of solitons with different the separation of solitons under the fixed pump power.When we increased the nonlinear effect of the cavity,the separation of solitons increased.At the same time,by using the long cavity and decreased the saturation fluence of the SESAM,a 12nd order of harmonic mode locking was achieved,and the multi-pulse mode of energy quantization effect in the experiment was proved.