Study On The Multi-soliton Dynamic Patterns In An Erbium-doped Fiber Laser Passively Mode-locked By Graphene Saturable Absorber

Compared with traditional saturable absorbers, graphene saturable absorberpossesses some unique optics merits, such as lower saturable intensity, widebandtunability, higher modulation depth, higher optical damage threshold and wavelengthindependent, and has been widely used in optical fields. Meanwhile, graphene haslarge nonlinear Kerr effect, which is approximately109times larger than that of silica.Due to its excellent saturable absorption and large nonlinear Kerr effect, graphenemode-locked fiber laser has been a well-controlled platform for studying of variousnonlinear optics phenomena. Originally, the formation of multi-soliton among thesenumerous nonlinear optics phenomena has attracted much attention. Understandingthe mechanism of multi-soliton formation would contribute to improve theperformance of lasers and deepen people’s understanding of nonlinear optics. In thispaper, we prepared the graphene mode-locking component through the mechanicalexfoliation method and experimentally studied the multi-soliton dynamic patterns inan erbium-doped fiber laser passively mode-locked by graphene saturable absorber.The main contents are summarized as below:1. Graphene mode-locking component was prepared by mechanical exfoliationmethod. The flakes of high oriented pyrolytic graphite were peeled repeatedlythrough a Scotch-tape and few layer graphene can be obtained. It was afterwardsdeposited on a standard FC/PC fiber connector due to the adhesive Van der Waalsforce just by pressing.2. A ring cavity passively mode-locked erbium-doped fiber laser based on theprepared graphene component was set up, and the output of stable soliton pulse wasobtained. When the pump power was increased to174.1mW, the mode-lockingoperation was achieved. The output power was0.67mW and the fundamentalrepetition rate was1.646MHz. The center wavelength of the mode-locked solitonwas1568.3nm with a3dB spectral width of about1.61nm and the pulse durationwas1.656ps. We experimentally studied the ordered multi-soliton, chaotic multi-soliton and soliton bunching, and the formation of these patterns were explained bythe peaking power clamping effect and a continuous wave (CW) induced globalsoliton interaction. 3. Passive harmonic mode-locking in the ring cavity erbium-doped fiber laserbased on graphene was achieved. We obtained stable harmonic mode-locking such asthe orders of11,15,19,27,37and47, and the corresponding repetition rates were18.11,24.69,31.27,44.44,60.90and77.36MHz. Further, the role of CW componentin the harmonic mode-locking was investigated. And we analyzed the properties ofharmonic pulses and the influence of pump power on the harmonic mode-locking.The relation between the multi-soliton patterns and the pump power was concluded aswell.