Research On The Tunable-dispersion Chalcogenide Multi-cladding Fiber

Mid-infrared supercontinuum sources have attracted wide attention due to their potential applications in optical infrared coherence tomography,metrology and spectroscopy.Due to the intrinsic absorption limitation of the material,the silica fiber cannot produce the mid-infrared SC above 2.4?m,so it is necessary to find a suitable glass material as the mid-infrared nonlinear fiber material.Tellurite glass,fluoride glass,and chalcogenide glass are the main materials for the research of the mid infrared fiber material materials.Besides,chalcogenide glass has a very high nonlinear characteristic and which is the only glass material theoretically covering the near,mid and far infrared wavelengths.Se-based chalcogenide glass is the basic material of chalcogenide glass.It is widely used and has a wide infrared transmission range(3-12 m),covering the fingerprint region of various molecules.Therefore,Se based chalcogenide glass is a hot candidate material for SC generation in the mid infrared.In order to obtain a wide SC broadening,the researchers usually choose to pump at near zero-dispersion wavelength(ZDW)in the anomalous dispersion region,but because the ZDW of the general Ch Gs fiber is>4.5?m,the OPA or OPO lasers pumping source must be carried out as pumping source,which will not be conducive to the miniaturization of the supercontinuum source.This paper is divided into two parts.Firstly,the research status of dispersion-regulated sulfur series multi-cladding optical fiber is investigated,and it is found that it has the advantages of easy tuning of dispersion,high nonlinearity and high coherence.According to the advantages of Se based materials,two kinds of optical fibers with different structures and different dispersion curves are designed by numerical simulation.The dispersion of materials is regulated by fine-tuning components,and the dispersion of waveguides is regulated by structural optimization.Finally,different dispersion curves and supercontinuum analysis are formed.In the first part,component optimization was firstly carried out for As₂Se₃,Ge₁₀As₂₂Se₆₈,As₂Se₃ and As₂S₃ to improve the structure parameters of the multi-cladding fiber to adjust the dispersion.The double-zero dispersion curve was obtained by simulation,and a variety of optical performance parameters of the multi-cladding fiber were numerically simulated.In this paper,the prefabricated rod of composite simulation structure was fabricated by the new two-step extrusion method and the fiber was made by drawing.Finally,the femtosecond laser and OPA were used to pump the As₂Se₃ fiber in the normal dispersion region near the zero-dispersion wavelength,and the SC output with the coverage range of 1.3-12.9?m was obtained.The second part is the component optimization based on the theoretical research of the first part.The fiber core material is changeless,by reducing the refractive index of fiber core with the first cladding composition difference form relatively flat dispersion curve,and change the outer material composition,to replace the outer cladding As₂S₃ materials for Ge₇As₂₃S₇₀,make the dispersion curve more flat,using the improved WI refractive index distribution to achieve the final fiber material selection,eventually forming As₂Se₃,As₃₈Se₆₂,As₂Se₃ Ge₇As₂₃S₇ chalcogenide multi-cladding fiber.Through theoretical simulation of cladding diameter changing waveguide dispersion,a full positive dispersion curve is finally obtained,and the SC output under different pumping power and pumping wavelength is analyzed by using the generalized nonlinear Schr?dinger equation.Finally,the paper summarizes the work content and points out the shortcomings of the research work.