Investigation On Ultra-fast Pulse Fiber Laser Based On Novel Two-dimensional Ternary Materials

Ultrafast fiber lasers have significant potential in high-speed communications,material processing and medical diagnosis owing to their superior characteristics,such as compact structure,large pulse energy,good heat dissipation performance and high effiency.In passively Q-switched and mode-locked techniques,using the real saturable absorbers(SAs)is a simple and the most effective method to obtain ultrafast pulses.The performance of saturable absorbers directly affects the output pulses performance of mode-locked laser.Since the first usage of atomic layer graphene to mode-locked fiber lasers,researchers pay more attention to the investigation and application of new 2D materials in ultrafast photonics.Compared with the many binary materials,ternary transition metal dichalcogenides provide the more freedom to regulate its energy band gap.In this paper,we experimentally studied the Q-switched and mode-locked fiber lasers based on ternary transition metal dichalcogenides.The main research contents of this paper are as follows:1.A few layers of ReS1.02Se0.98 saturable absorber was prepared by mechanical exfoliation.The nonlinear absorption characteristics of ReS1.02Se0.98-SA are obtained by a twin detector technique.The results indicate a modulation depth of?2.9%and saturating intensity of?0.13 MW/cm2 at 1030 nm.For the first time,we built an all normal dispersion ytterbium-doped fiber ring resonator to achieve stable Q-switched pulse operation.The narrowest width of the Q-switched pulse is 2.22 ?s,the center wavelength is 1035 nm,the repetition frequency ranges from 21.66 to 31.33 kHz,and the maximum output power is 2.96 mW,corresponding to a maximum single pulse energy of 81.47 nJ.2.The ReS1.02Se0.98-SA was applied to an all normal dispersion ytterbium-doped mode-locking fiber laser,and the noise-like pulses operating was realized by optimizing the parameters of cavity and components.The average pulse width of the spike is 283 fs on the top of a 16.3 ps broad pedestal and the central wavelength is 1032 nm with the spectral width is 3.9 nm.And the maximum output power is 91.9 mW,corresponding to a single pulse energy of 2.64 nJ.3.A high-quality saturable absorber based on a two-dimensional ternary chalcogenide Ta2NiS5 nanosheet has been successfully fabricated.Based on the twin-detector technique,nonlinear optical absorption of the Ta2NiS5-SA is characterized by 64.7%and 11.95%modulation depths with 1.3 and 0.72 MW/cm2 saturation intensities at 1028 nm and 1570 nm,respectively.4.The Ta2NiS5-SA is integrated into Yb-doped fiber laser cavities for the first time.Q-switched pulses were obtained at a pump power of 240 mW.The modulation range of the repetition rate and the full width at half maximum(FWHM)of the pulse duration were observed as 104.6?212.3 kHz and 1.72?1.13 ?s,respectively,by changing the pump power.The central wavelength of the laser signal located at 1029 nm.At the pump power of 320 mW,the maximum single pulse energy is 117.2 nJ,the shortest pulse duration is 1.07 ?s.Combining Ta2NiS5-SA with the nonlinear polarization rotation effect,the mode-locked pulse with a pulse width of 10.15 ps was realized in an Yb-doped fiber laser.The central wavelength is 1029 nm,the spectral width is 6.8 nm,and the pulse repetition frequency is 37.27 MHz.5.The Ta2NiS5-SA is integrated into Er-doped fiber laser cavities for the first time.Self-starting Q-switching operation is achieved,when the pump power is 100 mW.With increasing pump power,the repetition rate is tuned from 30.02 to 137.6 kHz,whereas corresponding pulse duration decreased from 5.8 ?s to 1.55 ?s.And the corresponding the narrowest pulse width,the maximum output power and the center wavelength are 1.55 ?s,72.11 nJ and 1561 nm,respectively.By optimizing intra-cavity dispersion,the mode-locked pulse with a pulse width of 1.45 ps is obtained for the first time.The center wavelength is 1569 nm with 3 dB bandwidth of?4.89 nm.The pulse repetition rate is about 2.92 MHz.And the maximum output power is 18.6 mW,corresponding to a single pulse energy of 6.37 nJ.