Investigation Of Er³⁺-doped Phosphate Glass And Fiber For L+ Band Optical Amplification

In recent decades,long-distance optical fiber communication technology has achieved great breakthroughs.How to further expand the communication capacity has always been a key research problem in this field.Especially in the wavelength region from 1450 nm to 1650 nm,the traditional erbium-doped fiber amplifier（EDFA）uses quartz as the main gain medium,the problems such as low rare-earth ion doping concentration and small gain bandwidth greatly limit the further development of communication technology.At the same time,with the rapid development of basic industries and integrated optics,fiber amplifiers with high gain,low cost,and small size are gradually favored by users and widely used in civil and military fields.Therefore,the search for a new type of matrix glass with high gain and wide bandwidth is of great significance for the development of optical fiber communication and optical fiber amplifiers.Compared with the traditional silica fiber,the phosphate glass fiber has the advantages of high rare earth doping concentration and large gain per unit length,which is convenient for integration,and its spectral properties are easy to control.In this paper,erbium-doped phosphate glass for optical amplification in L+band（from 1600 nm to 1630 nm）is taken as the research object,and the spectral properties of erbium-doped phosphate glass are analyzed for the purpose of broadening the fluorescence bandwidth of erbium-doped phosphate glass in L+band.And the anti-devitrification performance of erbium-doped phosphate glass is improved by changing the glass network modifier to ensure the successful drawing of the optical fiber.In this paper,erbium-doped phosphate glass of Al₂O₃-Ba O-Na₂O-Li₂O-P₂O₅-Er₂O₃（B series）system was prepared by traditional melting method,and the effect of Ba O replacing P₂O₅on the spectral properties of erbium-doped phosphate glass in L+band was studied.By comparing the normalized fluorescence spectra,it was found that with the increase of Ba²⁺content,the flatness of the L+band improved.When the introduction amount of Ba O is 28 mol%（B28）and 31 mol%（B31）,the flatness in the L+band is better than other samples.The structural changes of the glass were explained by the comparative analysis of Raman spectroscopy.With the increase of Ba²⁺content,the main group constituting the phosphate glass changes from phosphorus-oxygen tetrahedron Q1 to Q2,and the local environment of Er³⁺changes significantly,resulting in different spectral properties of samples in the L+band.On the basis of B series glass,doping with B₂O₃improves the anti-devitrification performance of the glass,replacing Ba O with Zn O improves the anti-devitrification performance and spectral performance,and Al₂O₃-Zn O-Na₂O-Li₂O-P₂O₅-Er₂O₃（Z series）system of glass was prepared.Through heat treatment of glass samples with different Zn O contents combined with differential thermal analysis,it was confirmed that the glass with Zn O content of 28 mol%（Z28）had the best anti-devitrification performance.In addition,comparing the spectral properties of Z28 and B28glass,it is confirmed that the amplification performance of Z28 glass in the L+band is also better than that of B28 glass.Z28 glass is used as the core component,and the cladding component is designed according to this component.The refractive index difference between the core and the cladding is 0.005,and the numerical aperture of the fiber is about 0.125.The fluorescence spectrum of the fiber confirms that the gain of the phosphate fiber in the L+band is significantly higher than that of the silica fiber.This work innovatively uses quartz glass crucible and graphite mold in the glass preparation process,which plays an important role in the water removal process and annealing treatment of phosphate glass,and has guiding significance for the preparation of phosphate glass.It has successfully prepared erbium-doped phosphate glass and optical fiber for L+band optical amplification,while ensuring the glass has excellent spectral properties and fiber-forming properties,providing an important reference for the design and preparation of high-performance optical amplification materials.