Research On Fabrication And Supercontinuum Generation Of Chalcogenide Microstructured Fibers

Supercontinuum(SC)is a kind of spectrum that narrow-band ultrashort laser pulse spreads in the nonlinear optical medium,through the combination of dispersion and nonlinear optical effects of the medium,making the spectrum of the incident pulse broadened.SC is applied in many fields such as optical frequency combing,air pollution monitoring,disease diagnosis and food quality monitoring due to its unique advantages such as good spatial coherence,high brightness and wide spectral bandwidth.At present,the nonlinear optical fiber matrix materials used to generate mid-infrared(MIR)SC include tellurite glass,fluoride glass,and chalcogenide(Ch G)glass,among which Ch G glass is the only fiber matrix material that can generate SC covering the far infrared bands because of its excellent IR transmission window and extremely high nonlinear refractive index.In order to obtain high-quality and wide-bandwidth SC output,further increasing the non-linear coefficient(g)of the Ch G fiber is necessary.There are two main methods,one is to taper the fiber,and another is to design a microstructured optical fiber(MOF).The taper waist of the tapered fiber is always too thin,which causes the fiber to withstand low laser power and is difficult to apply in practice.MOF not only has flexible structure design and good mechanical strength,but also can withstand high laser power,which is beneficial to practical applications.In many practical applications,the SC spectrum light source needs to have a wider output width and higher output power,and also requires to have high coherence,such as ultrashort pulse generation,frequency metrology,and optical coherence tomography.A common approach to obtain coherent SCs is pumping fibers with an all-normal dispersion(ANDi)profile by femtosecond lasers.At present,there are few reports on high coherent ultrabroadband MIR SC output based on ChG MOFs.In this paper,Ge₁₅Sb₁₅Se₇₀ glass with high laser damage threshold,good thermal stability,and difficult to crystallize is selected in Se-based glass as the fiber matrix.Ge-Sb-Se SCFs with different duty ratios(d/(43))are firstly fabricated,the dispersion characteristics are numerically simulated,and the SC output of 1.5?12?m is obtained through experiments.With the decrease of the fiber core diameter,the zero dispersion wavelength(ZDW)of the fiber can be effectively blue shift,but the fiber cannot be achieve ANDi profile.In order to obtain a highly coherent SC output,in terms of fiber structure design,it is considered to increase the waveguide dispersion of the fiber to compensate the fiber material dispersion to obtain a MOF with ANDi profile.Based on the research of Ge-Sb-Se SCF,a Ge-As-Se-Te/As-S AS-MOF with ANDi profile is designed and fabricated.The effect of the wavelength and power of the pump laser pulse on the SC output is studied,and finally a high coherent 2?13.2?m ultrabroadband SC is obtained.