Research On The Characteristics Of Fiber Laser Based On Tin Diselenide Nanomaterials

Pulsed lasers are widely used in industrial processing,biological detection,laser sensing,laser communication,and medical surgery.Compared with traditional lasers,fiber lasers have the advantages of simple and compact structure,good beam conduction performance,high energy conversion rate,good heat dissipation,low cost,and stable performance.They are the best choice for pulsed laser light sources.In addition,the use of the fiber's own nonlinearity and dispersion can generate pulses of various properties in the fiber laser cavity,thereby meeting different application requirements in various fields.In order to make the fiber laser work in the pulse output state,the most effective methods are Q-switched and mode-locked technology.At present,the most popular research direction is to obtain passive Q-switched and passive mode-locked pulses by saturable absorber.In recent years,researchers have used various materials with nonlinear optical properties as saturable absorbers to achieve the output of Q-switched and mode-locked pulses.Among them,two-dimensional materials are the most popular.Since the advent of two-dimensional materials in 2004,researchers have been enthusiastic for their excellent nonlinear optical properties,adjustable band gap structure,ultrafast electron relaxation time,and high damage threshold.Two-dimensional materials such as graphene,transition metal sulfides(TMDs),topological insulators(TI),and black phosphorus(BP)are used as saturable absorbers in fiber lasers to achieve the output of Q-switched and mode-locked pulses.It has been widely reported.But this is just the beginning of the growing 2D material family.This paper mainly studies the nonlinear optical properties of a new two-dimensional material tin diselenide(SnSe2)and the use of its saturable absorption characteristics to obtain Q-switched and mode-locked pulses of different solitons in a ring erbium-doped fiber laser.The tin diselenide nanomaterials used in the experiments were prepared by solvothermal method.Then,the prepared materials are systematically characterized,including:SEM,TEM,STEM,EDS,XRD,ultraviolet-visible spectrum,and Raman spectrum.The saturable absorption device uses optical deposition to deposit materials onto a homemade tapered fiber.In order to meet the requirements of the experiment,the prepared tapered fiber must meet certain conditions.The tapered fiber must strictly control its loss below 40%,and the diameter of the tapered region should be controlled around 20 ?m(the error range is ±5 ?m).Such a tapered fiber can ensure the output power of the laser and the interaction between the evanescent wave of the laser and the material.Then,the material is deposited.The prepared tin diselenide is dissolved in acetone,and fewer layers of tin diselenide nanosheets are obtained by the liquid phase stripping method for more than two hours.The material is then deposited on the tapered optical fiber by optical deposition.At the same time,the loss of the tapered fiber of the deposited material is controlled to be less than 50%.The optical nonlinear absorption of tin diselenide was measured using a double-balanced system built by the laboratory.It was measured twice in total,with a three-month interval between the two times.The corresponding modulation depths were 6.38%and 5.52%,respectively.In addition,comparative experiments were performed in two ring erbium-doped fiber laser cavities with different losses.The effects of the laser cavity loss on the generation of pulse types and the effects of changing the polarization state on the generation of solitons in the same cavity are compared.Q-switched pulses were obtained in a cavity of a 0.5-m long gain fiber and a 50:50 optical coupler.The repetition rate of the Q-switched pulses is 67.1-100 kHz,and the corresponding pulse duration is 4.5-1.8 ?s.In another cavity,a mode-locked pulses can be obtained using a 0.75-m long gain fiber and a 40:60 optical coupler.The mode-locked pulses obtained by changing the polarization state are traditional soliton,bound state soliton and harmonic pulses.Among them,the 3-dB spectral width of the traditional soliton pulses with a fundamental repetition rate of 8.3 MHz is 2.7 nm,and the corresponding pulse duration is 964 fs.Secondly,the spectral modulation period of the bound soliton is 1.2 nm,which corresponds to the modulation period of 6.4 ps in the autocorrelation track,and the pulse duration is 882 fs.Finally,the 3-dB spectral width of the harmonic pulses up to the 31st order is 2.9 nm,and the corresponding pulse duration is 887 fs.