Studies On The Characteristic Control Of Soliton In Passively Mode-locked Fiber Laser

Ultrashort pulse laser have been widely applicated in fiber telecommunications,biomedical diagnostics,and industrial materials processing.Passively mode-locked fiber lasers are effective sources to generate ultrashort pulses and have been attracted a great deal of research interest due to with the excellent compact cavity design,low cost,and environmentally stable performance.In this dissertation,we have experimentally and theoretically investigated the characteristics control of solitons.The contronl of the soliton sideband,the variation of the soliton fearthers due to the cavity dispersion,the contron of the soliton wavelength and pulse duration are mainly studied.The main research contents of this dissertation are as follows:1.By appropriately adjusting the polarization controller(PC)of laser cavity,the conventional Kelly peak sidebands,peak-dip sidebands,and dip sidebands appear in the soliton spectra,respectively.The peak-dip and dip sidebands exhibit distinct characteristics from the conventional peak sidebands.The formation mechanism of the new type sidebands can be attributed to soliton experience period-doubling bifurcation in the cavity.We have proposed a sideband-controllable fiber soliton laser by means of chirped fiber Bragg gratings(CFBGs).Each side of the spectral sidebands of laser could be removed by using a CFBG with proper dispersion.The numerical and experimental investigations show that the generation of the unilateral sidebands is attributed to the CFBG-induced spectral filtering effect.2.By using dispersion managed technique,the conventional soliton,dispersion-managed soliton and disspative soliton are delivered from the nanotubes-mode-locked fiber laser,respectively.We have study the evolutions of solitons spectrum and pulse characteristics depending on the pump power,respectively.The dynamic processes of the soliton formation and splitting are also been numerically and experimentally investigated.We have also proposed a novel cavity which could directly generate two different mode-locked pulses,such as conventional soliton and disspative soliton,or dispersion-managed soliton and disspative soliton,simultaneously.3.Due to the variation of the gain spectrum of erbium-doped fiber,the central wavelength of the mode-locked pulse can be switched from about 1531 to 1557 nm.The formation and evolution of the switchable soliton operation are investigated numerically with the appropriate gain profile.With the NPR-related filtering effect,the disspative soliton could be widely tuned over the range from 1566 to 1593 nm by adjusting the PC state in nanotubes mode-locked fiber laser.Based on the round-trip model,the formation of the tunable operations is investigated in the simulations.We propose a compact nanotube-mode-locked all-fiber laser based on three CFBGs,delivering three lasing wavelengths simultaneously.The output central wavelengths are 1539.5,1549.5,and 1559.5 nm,respectively,which can be accurately selected by CFBGs.The output wavelengths are tunable by stretching CFBGs.4.We propose a nanotube-mode-locked all fiber laser that can directly deliver picosecond and femtosecond solitons simultaneously.The picosecond and femtosecond solitons are centered at 1539.5 and 1561 nm.The 3-d B widths of the spectra and the pulse durations for the picosecond and femtosecond solitons are estimated as 0.33 nm and 10.6 ps,6.2 nm and 466 fs,respectively.The two scale solitons in cavity have different propagation routes and can stably operate for several hours.Numerical results agree well with the experimental observations and clearly reveal that the dynamic evolutions of the picosecond and femtosecond solitons are qualitatively distinct in the intracavity.