| Ultrafast pulse fiber laser has been the focus of academic research and industry,including optical communication,optical sensing,laser precision processing and medical equipment,due to its high temporal resolution,high peak power,and short material interaction time.As the key device in ultrafast fiber laser,saturable absorbers(SAs)have great impact on the pulse dynamics.Based on diverse low-dimension nanomaterials,including graphene carbon nanotubes,topological insulator,and many others,researchers have widely studied in material fabrication and optical properties,which plays a positive role in the further research and development of ultrafast fiber laser.Indium tin oxide(ITO)is widely used as transparent conductive oxide because of its optical transparency,electrical conductivity,good adhesion with glass,good wear resistance and chemical stability.It is also expected to be a good SA for passively mode-locked fiber lasers due to its wide SA region,wide bandwidth,strong plasma absorption peak and large nonlinearity.In this thesis,a type of D-shaped-fiber-supported ITO-SA is introduced into mode-locked fiber laser.Rich soliton dynamics are realized in C-band,including typical soliton,soliton bound state,bound states of soliton bound,and vector soliton period bifurcation.It proves that ITO has great research potential and value in ultrafast fiber lasers.The research content mainly includes the following five parts:1.ITO-SA with reliable performance were fabricated by uniformly depositing ITO solution on the side polished D-shaped fiber.The used two types of D-shaped fiber were both made of standard single-mode fiber.The stripping length of cladding was 20 mm,meanwhile,the stripping depth was 52.5μm and 54.5μm,respectively.By drying the material,ITO-SA could be successfully prepared.The saturable absorption characteristics of ITO-SA were further characterized by femtosecond fiber laser.The modulation depth of ITO SA was 19.5%and 26.9%,respectively.2.The stable soliton output based on ITO-SA fiber laser is achieved.ITO-SA with 19.5%modulation depth is incorporated into a fiber laser with 7.22-m laser cavity.With 11.9m W pump power,soliton pulse output is achieved.The output power is 0.13 m W;The center wavelength is 1565.2 nm;The repetition rate is 27.7 MHz;The width of pulse duration is 369 fs;the corresponding 3 d B optical spectrum width is 5.1 nm;The signal-to-noise ratio is 63.9 d B.3.The dynamics of the double soliton bound state is studied experimentally and theoretically.With the pump power of 17.2 m W,double soliton bound state is realized.The output power is 0.26 m W;The pulse width is 541 fs;The time modulation period is2.51 ps;and the corresponding phase difference between adjacent pulses isπ。Furthermore,through corresponding numerical calculation,the experiment-consistent simulation results are obtained.The influence of the pump power of the fiber laser on the stability of the double soliton bound state is also studied.4.The bound state pulse operation of soliton cluster is realized.By increasing the pump power of the laser and adjusting the birefringence of the in-cavity resonator,the bound states of triple soliton cluster and double soliton cluster are realized respectively.With the case of triple soliton cluster,the pulse duration is 740 fs,and the time distribution between adjacent pulses is 2.6 ps.With the pump power of 30.2 m W,the bound state with double soliton cluster is obtained.The output power is 0.64 m W;The pulse width is 669 fs;The time interval between adjacent pulses is 1.96 ps;And the time interval between two bound state clusters is 17.05 ps.5.The vector triple periodic bifurcation(PTB)output is realized.A dispersion management fiber laser with a net dispersion value of-1.1 ps~2 is designed by using the ITO-SA with a modulation depth of 26.9%and some dispersion-shifted fiber.Under the accumulation of high nonlinearity,soliton pulse shows complex PTB.By adding polarization beam splitter out of the laser cavity,two orthogonal components both show PTB.It indicates that ITO materials have great potential in soliton dynamics. |
