Exploration On New Types Phosphate Microstructure Fibers

With the rapid development of information technology and the emergence of new optical devices,more requirements are placed on fiber materials and fiber devices.For example,high-power laser systems require fiber structure to improve pump efficiency and reduce fiber radiation damage.Coherent optical communication requires fibers to have polarization-maintaining performance;optical devices such as modulators,optical switches,and inverters require fibers to have high nonlinearity Optical effect.The traditional core-cladding fibers can not meet the requirements of optical devices.Therefore,this project had developed three new types of microstructured phosphate glass fibers.The content is shown as follows:（1）Firstly,the preparation of Er³⁺/Yb³⁺co-doped phosphate double-clad fibers was explored.The luminescence spectrum of phosphate glasses with different Er₂O₃ dopant were explored,and the optimum dopant of rare earth ions were determined to be 1 mol%Er₂O₃ and2 mol%Yb₂O₃.Then after the melting and cold processing of the core glass,the core rod with the diameter of 1.4-1.6 mm was drawn,which had Er³⁺ion doping concentration of1.184×10²⁰ cm^-3 and Yb³⁺concentration of 2.368×10²⁰ cm^-3.（2）The effects of different contents of BaO and fluoride on the physicochemical and thermal properties of phosphate glasses were investigated.The research showed that as BaO content increased,the density,hardness,refractive index,T_g and T_f of phosphate glasses gradually increased,the thermal expansion coefficient of glasses reduced,indicating that the mechanical performance and thermal performance of glasses improved,the network structure of phosphate glasses were strengthened.While fluoride（KF,CaF₂,BaF₂）was added to phosphate glasses,due to the weakening effect of the F^-on the glasses structure,the glasses structure became loose,and the mechanical performance and chemical stability of the glasses were deteriorated,which was not suitable for the preparation of optical fibers.Finally,the formulation of inner and outer cladding of fiber were determined to be56.7P₂O₅-10.5K₂O-4Al₂O₃-4.2La₂O₃-22.6BaO and 64.5P₂O₅-13K₂O-12CaO-2.5Al₂O₃-8B₂O₃.（3）Exploring and optimizing the bulk glasses melting process,including melting,aerating,water removal,etc.The bulk glasses without bubbles and streaks and with good uniformity and low hydroxyl content(1.16×10¹⁹ cm^-3)were prepared.The fiber preforms were prepared by tube-rod method after cutting,rounding,perforating,internal and external polishing.Then the Er³⁺/Yb³⁺co-doped phosphate double-clad fibers were drawn on the drawing tower.The core diameter was 78-81μm,the NA was 0.052,the inner cladding was277-282μm,the NA was 0.356,and the outer cladding was 1483-1518μm.The transmission loss of the double-clad fiber was 7.15 dB/m at 1310 nm,and the absorption coefficient of 976nm pump light was 253.9 dB/m.The laser performance of the phosphate double-clad fibers was investigated.And the ASE at 1.5μm appeared,its intensity firstly enhanced and then decresed with the length of double-clad fiber,and the strongest intensity was at 7.5 cm.（4）The preparation process of erbium-doped polarization-maintaining fibers was explored.The size and structure of the Er³⁺/Yb³⁺co-doped phosphate polarization-maintaining fiber were designed,and the fiber preforms were processed by the tube-rod method.Then the Er³⁺/Yb³⁺co-doped phosphate polarization-maintaining fibers were drawn on the drawing tower.（5）The preparation of nonlinear optical fibers were explored.Ba₂TiSi₂O₈microparticles were prepared based on a sol-gel combined electrospraying technique.The Ba₂TiSi₂O₈ microparticles were spherical in shape,had good dispersibility,high crystallinity and hollow structure.Ba₂TiSi₂O₈ microparticles had a frequency doubling effect excited by a1064nm picosecond laser.Subsequently,Ba₂TiSi₂O₈ microparticles would be doped in phosphate glass to prepare nonlinear fibers.