Study On Performance Of Fiber Laser Based On MoS₂ Composite

Fiber laser has more and more important application and status in optical communication,industrial production,biomedicine and so on.Compared with solid-state lasers,fiber lasers have many attractive advantages such as simple structure,low manufacturing cost and easy realization of miniaturization.With the advent of graphene lasers,the interest in two-dimensional atomic materials in the laser field has been opened up.In recent years,a variety of nanomaterials have been proved to have saturated absorption effect and applied in pulsed lasers.Carbon nanotubes,graphene,topological insulators,transition metal sulphides,gold nanorods and so on have been reported.But these two-dimensional materials have their own advantages and disadvantages.Although graphene has ultra-fast electron relaxation time,the light modulation depth of single-layer graphene is very low and easy to be damaged.Although the electron relaxation time of topological insulator is larger than that of graphene,its light modulation depth is larger and the threshold is higher,so it is not easy to be damaged.The band gap of the transition metal sulfide is wide,the threshold is high and the pump power is required.It is difficult to adjust the surface plasmon resonance peak of metal nanoparticles to the infrared region.This paper mainly studies the properties of saturable absorption device based on molybdenum disulfide composite and its application in all-fiber laser.NiS₂/MoS₂ composite was synthesized by two-step method for the first time,and the completed material was characterized by electron microscopy scanning,Raman,atomic force microscope and other characterization methods,indicating that NiS₂/MoS₂ was a petal-shaped flake structure prepared by two-step chemical synthesis.Then,z-scan and dual-arm detection methods were used to test the nonlinear properties of the material,and the modulation depth ₀?,nonlinear loss?_NS and saturation light intensity I_sat were obtained as 2.1%,34.1%and 0.34mW/cm²,respectively.Then NiS₂/MoS₂ composite materials mixed with PVA sol and through colorimetric dish into film,using the sandwich structure will complete composite film by two FC-PC will be added to the fiber laser cavity,by adjusting the polarization controller and pump power for laser tuning Q output,when the pump power increased from 150 mW to 400mW,the pulse repetition frequency increased from 7.98 kHz to 36.5 kHz,corresponding to the pulse width of us reduced from 63?s to 13.7?s,output power linearly increased from0.56 mW to 1.18 mW.When the pumping power is 250 mW,the central wavelength of the spectrum is 1561.8 nm,the bandwidth of 3 dB is 1.43 nm,and the signal intensity is close to55 dB.When the pumping power was increased to 400 mW,the spectrum barely changed within 14 hours,indicating the high damage threshold and high stability of this composite material.Then we proposed SnS₂/MoS₂ composite material,which was also synthesized by two-step method.Raman and atomic force microscope were used to characterize the SnS₂/MoS₂ composite.It was proved that the SnS₂/MoS₂ prepared by two-step chemical synthesis method presented a lamellar structure with only a few layers.Then,the optical deposition method was used to transfer SnS₂/MoS₂ composite material to the end face of the fiber jumper to form a mode-locking device.The mode-locking device was coupled into the ring cavity of the fiber laser to adjust the polarization controller and pump power,and the passive Q modulation of the baited fiber laser was realized.When the pump power increased from 200 mW to 450 mW,the pulse repetition frequency increased from 7.387 kHz to 9.492kHz,the corresponding pulse width decreased from 305.9?s to 85.4?s,and the output power linearly increased from 0.452 mW to 1.14 mW.When the pump is 330 mW,the central wavelength corresponding to the spectrum is 6.4 nm,the bandwidth of 3 dB is 0.2 nm,and the spectral signal strength is up to 56 dB.When the pumping power was increased to 450 mW,the pulse and spectrum remained stable,and the spectrum barely changed within 14 hours,indicating that SnS₂/MoS₂ composite also had high damage threshold and high stability.