Design Of High Stability Graphene Based Mode-locking Fiber Laser

Graphene was discovered in 2004 and after a few years in 2010 discoverers won the Nobel Prize.The two-dimensional carbon material graphene has various aspects of good qualities,which attract wide interest of global researchers,giving birth to a series of remarkable results.Because of the the high transparency,high electron mobility,strong nonlinear Kerr effect and saturable absorption characteristics of graphene,it has wide applications in the optoelectronic field,such as touch-screen,high speed photo-detectors,optical polarizer and mode-lock fiber laser,etc.Also,the excellent properties of the graphene make it suitable for the fabrication of wide bandwidth,high data rate and high responsibility optoelectronic devices.In all the applications,graphene based mode-locked fiber laser is among the attractive ones.Graphene has a strong saturable absorption property and a fast recovery time,which can be used in fiber lasers as the saturable absorber to realize mode-locking and generate ultra-short pulses.The key issues in the fabrication of graphene based saturable absorber are trying to increase the interaction between graphene and the light field,and also,to find the simple,effective method to transfer the graphene samples onto the fiber.In order to enhance the interaction between graphene and light field,and increase the saturable absorption property and modulation depth of the SA,we propose to transfer CVD monolayer graphene covered with 100 nm gold film onto a moderate-polished D-shape.The gold film helps increase the polarizing property,increase the interaction between graphene and the evanescent field and protect the graphene sample as well.Besides,we modified the fiber polishing process to achieve more stable polished fiber with flatness.We achieve polarized saturable absorber with 5dB IL and 14% modulation depth.303 fs,12nJ and 263 fs and 13.65 nJ soliton pulses are obtained by using the two kinds of graphene saturable absorber as modelocker in the fiber laser.Further more,we manage the dispersion in the cavity and obtain 105 fs and 7.4nJ ulstra-short pulse.And then we fabricate a fiber laser product using the gold-coated graphene saturable absorber.The stability of the laser product has also been tested.Besides,in order to improve the stability of the mode-locked fiber laser,we put forward a set of graphene mode-locked fiber laser light path and feedback circuit of the implementation plan.Combining the idea of simulated annealing algorithm with our experience of manually adjusting the polarization of the fiber laser cavity,we realize the auto mode-locking function of the graphene fiber laser and improve its stability.