| Ultrafast laser pulses have many applications,ranging from basic research to industry,e.g.,optical communications,optical fiber sensing,laser surgery,laser precision machining,laser amplifier seed source,nuclear fusion,light-material interaction,the optical frequency comb.Compared to other lasers,fiber laser has a simple and compact design,efficient heat dissipation,and high-quality pulse generation.Fiber laser has attracted much interest in generation of ultrafast pulse.However,the energy of traditional soliton is generally limited by optical wave breaking and below 0.1 nJ.Therefore,achieving high-energy wave-breaking-free pulses is needed in the fiber laser system.In the normal dispersion region,self-similar parabolic pulse is a candidate to overcome the limitation of pulse energy,which has a monotonic frequency chirp and parabolic profile.Compared to traditional soliton,dissipative soliton can keep high energy and overcome wave breaking,which has different formation mechanism.In this paper,we present a conceptual model of a fiber laser at 2.8 μm using the NPR technique for evolution of self-similar parabolic pulse.A dissipative soliton Yb-doped mode-locked fiber laser at 1-μm regime with bismuthene saturable absorber(SA)via evanescent field interaction is demonstrated for the first time.The main works of this paper are as follows:1.The parabolic pulse evolution in a mode-locked Er-doped fiber laser operating at 2.8 μm has been numerically investigated.By utilizing a segment of chalcogenide dispersion-decreasing bandgap fiber and a piece of Er-doped ZBLAN around 2.8 μm,stable parabolic pulses can be obtained in the soft-glass fiber resonator.The output pulses are analyzed when the polarizing angles changes from 0.356 π to 0.4 π and the net group velocity dispersion from 0.006 ps2/m to 0.03 ps2/m,respectively.The influence of different initial pulse and evolution of pulse polarization states in cavity are discussed.Through optimizing the dispersion(i.e.net dispersion is 0.014 ps2/m),the pulse with 7.35-ps duration and 1.7-nJ pulse energy can be obtained,which has a parabolic profile.The ratio of maximum to minimum pulse width in the cavity is about 10.The pulse energy and K parameter increase with the increase of the net dispersion.As the net dispersion increases to 0.03 ps2/m,the pulse energy can reach up to 2.5 nJ.These results can be regarded as guidance to design a wave-breaking-free fiber laser in mid-infrared region.2.We demonstrated a dissipative soliton Yb-doped mode-locked fiber laser at 1-μm regime with bismuthene saturable absorber(SA)via evanescent field interaction for the first time.In the experiment,we show the characterization and optical properties of bismuthene.The bismuthene saturated absorber is prepared by optical deposition method on a self-made microfiber with a beam waist diameter of 15 μm.The nonlinear optical absorption of microfiber-based bismuthene SA has been experimentally illustrated by using home-made ultrafast fiber laser.The saturation intensity and modulation depth of SA are about 13 MW/cm2 and 2.2%,respectively.Relying on the excellent nonlinear optical property of the bismuthene SA,typical dissipative soliton with repetition rate of 21.74 MHz is generated at a center wavelength of 1034.4 nm.The time-bandwidth product of the pulse is about 23.07 with pulse width of 30.25 ps.The results demonstrate that the bismuthene is a good candidate to apply in 1-μm wave-breaking-free mode-locked fiber laser and nonlinear photonics components. |
PDF Full Text Request