Study On Ultrafast Fiber Laser Based On Saturable Absorber Of Antimony Two-dimensional Materials

Passively mode-locked/Q-switched mechanism based on saturable absorbers（SAs）is the most widely used modulation method in the field of ultra-fast fiber laser.Inthis paper,based on two antimony two-dimensional（2D）materials as SAs,the output characteristics of passively mode-locked/Q-switched erbium-doped fiber laser are studied.Based on the rich and varied pulse output obtained in erbium-doped fiber laser,the output characteristics of erbium-doped fiber laser modulated by two antimony 2D materials as SAs are analyzed:（1）Erbium-doped mode-locked pulsed fiber laser based on saturable absorber of InSb.InSb SA was prepared by magnetron sputtering deposition and a variety of soliton mode-locked pulse were obtained in erbium-doped fiber laser.（1）Erbium-doped conventional soliton mode-locked fiber laser based on InSb SA.A6.8 m laser ring resonator is constructed,and a stable conventional soliton mode-locked output is obtained in the range of pump power 150～400 m W with the insertion of InSb SA.When the pump power is 400 m W,the central wavelength of the spectrum is 1570.38 nm,the 3d B bandwidth is 8.26 nm,and it has typical characteristics of conventional soliton spectrum.The pulse duration is 540.74 fs,the basic repetition rate is 28.38 MHz,signal-to-noise ratio 57 d B,and the maximum output power is 5.51 m W.It is fully demonstrated that InSb nanosheets have good saturable absorption properties and can be used for femtosecond ultrashort pulse output.（2）Soliton molecular mode-locked erbium-doped fiber laser based on InSb SA.Based on conventional soliton mode locked,various soliton molecular outputs have been obtained,and the pulse output characteristics have been analyzed.Soliton molecules exist stably in the range of pump power from 200 to 280 m W.By adjusting the polarization controller,a double soliton tightly bound soliton molecule output with a soliton interval of 2.25 ps and a spectral modulation period of 3.65 nm can be obtained.The output of a double soliton loosely bound soliton molecule with a soliton interval of 23.40 ps and a spectral modulation period of 0.31 nm.And the output of three soliton loosely bound soliton molecules with soliton interval of 16.04 ps and 20.38 ps,and spectral modulation periods of 0.06 nm and 0.14 nm.The signal-to-noise ratios of the three soliton molecules are 57 d B,56 d B and 55 d B,respectively,which show the high stability and reliability of the system.（2）Q-switched mode-locked erbium-doped fiber laser based on InSb SA.By adjusting the cavity parameters,an annular cavity with a length of 13.92 m was built.With the insertion of InSb SA,stable Q-switched mode-locked pulse output was obtained in the range of pump power from 160 to 300 m W.Its main feature is that the amplitude of a stable mode locked pulse sequence is modulated by a periodic Q-switched envelope.As the pump power increases,the repetition frequency of the Q-switched envelope increases,and the width of the envelope decreases.The maximum pulse envelope repetition frequency is66.32 k Hz,and the narrowest pulse envelope width is 3.80μs.The output spectrum is centered at 1566.67 nm with a 3d B bandwidth of 1.57 nm.The maximum output power and pulse envelope energy reached 8.00 m W and 119.74 n J,respectively.The experimental results based on modulating an erbium-doped fiber laser using an InSb SA show that,on the one hand,the prepared InSb SA has a high damage threshold,excellent long-term stability,and outstanding antioxidant ability,making it an excellent SA.On the other hand,the obtained experimental results greatly enrich the understanding of conventional soliton and soliton molecule mode-locked lasers,and deepen the understanding of InSb 2D materials.（3）Erbium-doped Q-switched fiber laser based on Sb₂Se₃SA.Sb₂Se₃SA was prepared by liquid phase exfoliation method,and stable Q-switched pulse output was obtained in an erbium doped fiber laser.A laser ring resonator with a length of about 6 m has been built,and the Q-switched operation is stable in the range of pump power from100 to 400 m W with the Sb₂Se₃SA inserted into the cavity.As the pump power increases,the repetition frequency of the Q-switched pulse increases from 40.49 k Hz to 128.12 k Hz,the pulse duration was compressed from 7.57μs to 0.93μs.At a pump power of 400 m W,the maximum average output power was 2.16 m W,and the maximum single pulse energy was 16.89 n J.During the entire experimental period,the output of the system remained stable.The experimental results are helpful for a deeper understanding of the photoelectric properties of Sb₂Se₃,and this work enriches the research on ultrafast fiber lasers based on real SAs.