Study On Rare Earth Doped ZnF₂-AlF₃ Based Glass And Its Mid-infrared Luminescence Characteristics

Mid-infrared fiber lasers have the advantages of high-quality beam quality,good heat dissipation,easy miniaturization and integration.They have very important application prospects in various fields such as laser processing,medical treatment and military.Because the mid-infrared band laser has a strong penetration ability in the atmosphere,and many absorption peaks of atoms and molecules are also in this band,mid-infrared band laser has a good application prospect in military and medical fields.The fluoride glass material is commonly used in mid-infrared fiber because of its low phonon energy.Fluorozirconate based glass material is the most widely used among them,～3μm laser output of tens of watts has been achieved by using rare earth ion doped ZBLAN（ZrF₄-BaF₂-LaF₃-AlF₃-Na F）glass fiber as the gain medium.However,the poor mechanical properties,chemical stability,resistance to deliquescent and thermal conductivity of zirconium fluoride glass limit its further development in fiber lasers.Thus,fluoroaluminate based glasses with higher mechanical strength,chemical stability and glass transition temperature have a great advantage in realizing mid-infrared fiber lasers.Exploring methods to improve the luminous efficiency of rare-earth ions is helpful to further improve the performance of 3μm fiber lasers.In this paper,AlF₃-based glass is selected as the matrix material,and the phonon energy of the glass is reduced by introducing ZnF₂to partially replace AlF₃.The preparation of fluoroindate glasses doped with Er³⁺and Ho³⁺and their luminescence properties in the 3μm were systematically studied.The research results were listed as follows:1.The influence of different concentration of ZnF₂on the properties of ZnF₂-AlF₃based glass was studied.A series of glasses（ZnF₂-AlF₃-YF₃-SrF₂-BaF₂,ZAYSB）were prepared by melt-quenching method in a glove box under the protective atmosphere of dry nitrogen.By introducing ZnF₂,more stable glass with lower phonon energy and wider transmission window is obtained.The absorption coefficient of hydroxyl at～3μm of ZAYSB glass is only0.042 cm^-1.2.The effects of different concentrations of ZnF₂on the luminescence properties of Er³⁺and Ho³⁺doped ZnF₂-AlF₃based glasses in～3μm band were investigated.Er³⁺and Ho³⁺doped ZnF₂-AlF₃glass were prepared by melt-quenching method in a glove box under the protective atmosphere of dry nitrogen.Under the excitation of 980nm laser,the luminescence of ZnF₂-AlF₃glass doped with Er³⁺increases gradually at～3μm band and decreases gradually at～2μm band.Under the excitation of 655 nm laser,its luminescence in～3μm band is gradually enhanced.The up-conversion spectrum of Er³⁺doped ZnF₂-AlF₃based glass were observed under the 980 nm laser pumping.It was found that the up-conversion luminescence was also enhanced by introducing ZnF₂.3.Ho³⁺/Pr³⁺doped ZnF₂-AlF₃glass fiber was fabricated.We obtained 2861 nm lasing by using Ho³⁺-doped fluoroaluminate glass fibers as the gain medium.In the experiments,the gain fiber length was 15.5 cm and a 1150 nm fiber laser was used as the pump source.The threshold pump power was 120 m W and the maximum unsaturated output power was 128m W with a slope efficiency of 8.9%.