Research On Near-infrared Emission Properties Of Rare-earth Doped Tellurite Glasses

Erbium-doped Fiber Amplifier（EDFA）has the advantages of high gain,low noise and low signal distortion,and the amplification range corresponds to the lowest loss region（1530～1565 nm）of optical signal transmission,which has become the mainstream communication method of large capacity and long-distance transmission.As the core part of the optical fiber amplifier,the gain medium,the choice of its matrix material and the doping mode of rare earth ions have an important influence on the gain performance of the amplifier.However,the gain medium of the traditional EDFA is erbium-doped quartz glass,and its erbium ion doping concentration is low,resulting in a narrow gain bandwidth（30 nm）,which can no longer meet the increasing communication demand.Therefore,exploring and preparing optical fiber glasses with broadband amplification capabilities and studying the spectral characteristics of rare earth-doped glasses in the near-infrared band are of great significance to the development of ultra-wideband optical fiber communications.In this paper,tellurite glass with better thermal stability and higher rare earth solubility is selected as the matrix material,in order to broaden the emission bandwidth of rare earth doped tellurite glass in the 1.5μm band and analyze the rare earth doped tellurite glass in the near-infrared band.The optical properties of the glass are co-doped with a variety of rare earth ions and the glass matrix composition is changed.It focuses on the study of the spectral properties of broadband erbium-doped tellurite glass,the preparation and spectroscopy of Er³⁺/Yb³⁺,Er³⁺/Tm³⁺co-doped tellurite glass,the property testing and broadband amplification characteristics of Er³⁺/Yb³⁺/Tm³⁺/Pr³⁺doped tellurite glass.（1）In order to solve the problem of the bandwidth of Er³⁺single tellurite glass with narrow amplification,the effects of the tellurite glass matrix and Er³⁺doping concentration on the optical properties of Er³⁺doped tellurite glass in the 1.5μm band were studied.By comparing the absorption and emission spectra of two tellurite glasses,Te O₂-Zn O-La₂O₃ and Te O₂-Zn O-Na₂O when Er³⁺is doped,the solubility of the rare earths and the amplification bandwidth of the two glass matrices were analyzed.The spectral parameters were used to analyze the gain bandwidth performance of the glass matrix.The results showed that Te O₂-Zn O-Na₂O glass matrix is superior to Te O₂-Zn O-La₂O₃ glass in its dilute ion dissolving ability and bandwidth amplification capacity;when the doping concentration of Er₂O₃ is 0.5mol%,Te O₂-Zn O-Na₂O glass achieve an intense ultra-broad（FWHM=112 nm）,and the stimulated emission cross-section is 8.8×10^-21 cm².The product gain bandwidth of the two is much larger than that of other glass substrates.（2）In order to solve the problems of low utilization of Er³⁺doped tellurite glass for the 980 nm pump source and single amplification band,it is proposed to use the broadband absorption of the sensitizing ion Yb³⁺to improve the pumping efficiency.By doping with Tm³⁺which is close to the Er³⁺luminescence center to achieve dual-band broadband amplification of tellurite glass.The experimental results showed that the Er³⁺doped tellurite glass sample doped with 1 mol%Yb₂O₃ increases the absorption cross section by 8 times at 980 nm,and the fluorescence intensity at 1.5μm also increases nearly twice,and the full width at half maximum are increased to114 nm.When 0.5 mol%Er₂O₃ and 0.03 mol%Tm₂O₃ is doped in tellurite glass,one peak center of 1568 nm（FWHM 118 nm）and the other one peak center of 1800 nm（FWHM 192 nm）were obtained.Rare earth-doped tellurite glass emits broadband in two wavelength bands of 1.5μm and 1.8μm.（3）Aiming at the problem that the current EDFA cannot amplify the 1.3μm band（optical signal in the zero-dispersion window）and the praseodymium-doped fiber amplifier working in the 1.3μm band can’t use 980 nm LD as the pump source,this paper adopts a variety of rare earth ions co-doping methods.The spectral characteristics of Er³⁺/Yb³⁺/Tm³⁺/Pr³⁺doped tellurite glass in the near-infrared band were studied,and finally under the excitation of a 980 nm pump source,a peak center of 1.35μm（FWHM 140 nm）,a peak center of 1.53μm（FWHM 106 nm）and a peak center of 1.8μm（FWHM 140 nm）were obtained.Combined with the calculation of absorption spectrum,the maximum stimulated emission cross section of Er³⁺ion is7.255×10^-21 cm²,and the gain coefficient is 1.588 cm^-1;the stimulated emission cross section of Pr³⁺ion is 4.343×10^-20 cm²,and the gain coefficient is 16.838 cm^-1.The larger emission cross-section and gain coefficient indicated that the Er³⁺/Yb³⁺/Tm³⁺/Pr³⁺co-doped tellurite glass prepared in this paper is a promising near-infrared gain medium,providing a new glass matrix material for high-efficiency fiber amplifiers.