Research On The All-normal Dispersion Chalcogenide Glass Fiber

Mid-infrared supercontinuum sources have attracted wide attention due to their potential applications in optical infrared coherence tomography,metrology and spectroscopy.Supercontinuum requires high coherence in many fields,while supercontinuum with higher coherence can be achieved by pumping in the normal dispersion region.At present,research on all-normal dispersion fibers has involved various structures and materials.In this paper,we propose a double-clad Te-based chalcogenide glass fiber with a W-type refractive index profile.The Ge-As-Se-Te fiber structure parameters were detailed numerically analyzed.The simulation results show that the double-clad Te-based glass fiber optimized by the structural parameters can achieve the normal dispersion distribution of the full-mid-infrared working band.On the basis of numerical research,the optimized Ge-As-Se-Te fiber with all-normal dispersion distribution was prepared by multiple extrusion methods.At 5 μm,a 19 cm long fiber is pumped with ultrashort pulses(150 fs,1 k Hz)to generate a broadband supercontinuum(SC)covering 1.5-11 μm.The coherence performance of SC was studied by numerical simulation.The results show that a high coherent SC of 3.5-10.5 μm can be generated in this all-normal dispersion fiber.In summary,it is easy to achieve an all-normal dispersion distribution for Te-based glass fiber because of their large material ZDW.In this paper,we have investigated the dispersion characteristics of the all-normal dispersion fiber,and optimised the structure of Ge-As-Se-Te chalcogenide glass with large material ZDW.The parameters of double-clad fiber were improved to adjust dispersion.A new type of dispersion-adjustable double-clad fiber was designed,and the performance of fiber was further tested.Firstly,the research results and application in the all-normal dispersion chalcogenide fiber are briefly summarized recently,and the advantages of double-clad chalcogenide fiber in achieving all-normal dispersion in the infrared band are analyzed.Then,Te-based chalcogenide glass Ge20As20Se17Te43,Ge20As20Se15Te45 and Ge15As25Se15Te45 were selected for the fiber core,inner cladding and outer cladding,The three sample glasses were component optimised and prepared,and their physical properties were further investigated.The finite element method is used to calculate the dispersion of the double-clad fiber.The relationship between the dispersion and nonlinear characteristics of the double-clad fiber and the structural parameters were analyzed.The structural parameters of the all-normal dispersion distribution were selected,and the double-clad preform was prepared by extrusion using multiple extrusions and drawn into an ideal double-clad fiber.Then,ultra-short femtosecond pulse pumping was carried out to theoretically study and analyzed the nonlinear effect and laser broadening performance of SC.The numerical simulation results showed that the GAST new double-clad fiber was pumped in the normal dispersion region to obtain a wide and flat mid-infrared SC output covering 1.5-11 μm,and the coherence characteristics of the output SC when the double-clad fiber ultra-short pulse pumping was studied..Finally,we summarized the content of the paper,and pointed out the shortcoming of research.