Supercontinuum Generation And Tunability Of Chalcogenide Suspended Core Microstructured Fiber

Supercontinuum is an optical phenomenon produced by optical pulse in the process of nonlinear medium transmission.It has the characteristics of wide spectrum,good stability and coherence,so it has been widely used in many fields.However,most of the supercontinuum spectra reported at present can not be tuned or the tuning range can not be precisely controlled.Therefore,in this paper,a method to generate tunable supercontinuum is proposed.The suspended-core micro structured fiber with highly nonlinear arsenic selenide(As₂Se₃)as the core and toluene as the cladding can generate temperature-controlled tunable supercontinuum in the critical temperature range of toluene-90?110?.It has broad application prospects in the fields of material detection,spectroscopy and environmental analysis.Firstly,the structure design and material selection of suspended core micro structure fiber are carried out.The substrate material of the fiber is chalcogenide As₂Se₃,which has high nonlinear effect and wide mid infrared transmission range.The effects of core diameter,bridge width and air hole number on dispersion and loss are studied by using full vector finite element method and perfectly matched layer condition.Then,the generalized nonlinear Schrodinger equation and the split-step Fourier algorithm were used to simulate and optimize the supercontinuum generated by optical pulse in highly nonlinear suspended-core fiber.The effects of pump peak power,pump initial pulse width and fiber length on supercontinuum are studied.When the fiber core diameter is3?m,bridge width is 0.95?m,the number of air holes is two holes,the pump center wavelength is2.7?m,the pump peak power is 14k W,the initial pulse width of the pump is 350fs,and the fiber length is 3cm,the broadening range of the supercontinuum is 1.72?7.79?m,the average relative output power is-38.1d B,and the spectral flatness is 0.87.Based on the optimized suspended-core microstructured fiber,a temperature-controlled tunable supercontinuum method is obtained by filling the cladding with toluene.The tunability of supercontinuum in the critical temperature range of-90?110?for toluene is analyzed by using nonlinear Schrodinger equation and split step Fourier algorithm.The effects of core diameter,initial pulse width,peak power and temperature on tunable supercontinuum are studied.It is found that when the core diameter of the fiber is 3?m,the 1.20?m spectral width can be tuned at the critical temperature by using the pump source with 3.1?m central wavelength,20k W peak power and300fs pulse width;with the increase of the tunable spectral width,the spectral flatness decreases slightly,ranging from 0.89?0.92,which indicates that the supercontinuum spectrum remains flat.Therefore,tunable supercontinuum is more flexible and convenient in its application.