Low-dimension Materials Prepared By Highly Efficient Methods And Its Application In Pulsed Fiber Laser

Pulsed fiber laserhas been widely used in optical communication,industrial machining,national defense and medical treatmentfor its high stability,good beam quality,simple structure and easily integration.Up to now,the mainly two methods to produce pulsed laser are mode-locking and Q-switching.Saturable absorber(SA)is a kernel component in passive mode-locked or Q-switched lasers.Thus the SA's nonlinear optical property,processing complexity and fabricating cost might greatly affect the applications of pulsed lasers.The first generation of commercial used SA:semiconductor saturable absorber mirror(SESAM),has been widely used in fiber lasers.However,SESAM get some drawbacks,like complex fabricating and packaging process,high cost and narrow operation bandwidth.With the development of material science,some low dimension materials have been developed as SAs,one dimension(1D)materials,like carbon nanotubes(CNTs),gold nanorods,two dimension(2D)materials,like graphene,topological insulators(TIs),transition metal dichaldogenides(TMDs)and so on.The operation wavelength of 1D SA depends on the chirality or aspect ratio,which makes it difficult to obtain desired operation wavelength.Two dimension materials are extensively studied due to their wide band,low insertion loss,and fast response as SAs.The appearance of 2D material based SAs facilitates the development of ultrafast lasers in high power,low cost,compact structure and high efficiency.In this thesis,we focused on how to produce broadband,low cost pulsed fiber laser.Some specific researchresults are summarized about low dimension materials preparation,like graphene,topological insulator and so on,and their applications in pulsed fiber lasers.Main achievements are listed as below:(1)We realizedhigh quality graphene transferring,using a polymer free wet transferring technique.By this method,we could fabricate a fiber compatible graphene SA.Mode-locking and Q-switching operation were obtained using the prepared graphene as SA.Graphene is transferredonto fiber end facet with wet transferred technique.Without the assistant of PMMA,graphene could be transferred onto the fiber end facet with less steps.The fiber end facet is covered totally with graphene,and no wrinkle or crackle can be seen through optical microscope.The solvent is easily volatiled,so that the transferring introduces few impurities.Based on graphene on fiber end facet,we setup a pulsed fiber laser,and 1550 nm wavelength Q-switched and mode-locked fiber laser are demonstrated.(2)The high efficiency ultrasonic method was used to exfoliate bulk TI into nanocrystals.Broadband nonlinear optcal properties of fabricated TI nanocrystals had been proved.We tested few groups mixture ratio of organic solvents,and obtained the highest exfoliation efficiency organic solvents mixture ratio.Using hybrid organic solvents exfoliation,high quality Bi2Te3 nanocrystals dispersion is fabricated with a size about 20 nm.While the Bi2Te3 nanocrystals are introduced into fiber lasers as SA,broadband mode-locked fiber lasers are achieved.With different wavelength mode-locked fiber laser,dissipative soliton,conventionalsoliton and noise-like pulse have been observed.(3)Based on ultrasonication,high stability and high quality SnSe nanosheets were obtained.We had studied the nonlinear optical property of SnSe and saturable absorption was verified.Using SnSe nanosheets as saturable absorber,mode-locking output at 1 ?m was realized.We come up with a new SA:SnSe.High quality and stable SnSe nanosheets are prepared with direct ultrasonic process.The nonlinear response of SnSe nanosheets is studied with Z-scan technique,and the saturable absorption is observed.Based on this,SnSe nanosheets is introduced into a ring Ytterbium-doped fiber laser.Stable mode-locked pulse output has been achieved with pulse width and center wavelength of of 235.4 ps and 1068 nm,respectively.(4)Third order nonlinear optical property of organic-inorganic at optical communication band was studied for the first time.Ultrafast pulse output at optical communication band was obtained based on the nonlinear absorption of onganic-inorganic perovskite.Systematic study about third order nonlinear property of perovskite is executed.The filmy perovskite with modulation depth and saturable intensity of 13.58%and 6.4 WM/cm2,respectively.Perovskite possesses a nonlinear refractive index of 1.12×10-14m2/W.While the perovskite applied in an erbium doped fiber laser,mode-locked pulse is obtained with center wavelength 1555 nm and pulse width 661 fs.