Study On Spectral Properties And Fiber Preparation Of Heavily Tm³⁺-doped Multi-component Germanate Glass

Fiber lasers operating at 2.0?m band have great application value in military and civilian fields such as laser radar,laser medical treatment,laser ranging,laser remote sensing,and spectroscopy.High-gain Tm³⁺-doped glass fiber is the critical material for constructing high-performance 2.0?m band fiber lasers.And the realization of highly Tm³⁺doping concentration in laser glass is the prerequisite for the development of high-gain Tm³⁺-doped glass fiber.Pure quartz glass has an inherent phase separation zone,which results in a low doping concentration of rare earth ions(?2 wt.%).However,multi-component oxide glass has high solubility of rare earth ions and has become an ideal matrix material for high-gain glass fibers.Among them,the multi-component germanate(BGG)glass has both excellent optical properties and great physicochemical properties,and has become the excellent matrix material for the 2.0?m band fiber with the most prominent comprehensive advantages.However,the low doping concentration of Tm³⁺in the BGG glass fiber results in a low gain coefficient,which in turn limits the development of high-performance 2.0?m band fiber lasers.In this dissertation,the doping concentration of Tm³⁺in the multi-component germanate glass was greatly increased by optimizing the composition of the germanate glass and adjusting the network structure of the glass.Meanwhile,the BGG glass melting and fiber preparation technology and process were optimized.Finally,highly Tm³⁺-doped multi-component germanate glass single-mode optical fibers were successfully fbricated.The specific research content and results are as follows:(1)The effects of trivalent rare earth metal oxides Ln₂O₃(Ln=La,Y,Lu,Sc)and Nb₂O₅on the structure and spectral properties of Tm³⁺-doped BGG glasses have been studied.By adjusting the degree of freedom of the glass network structure,the dispersion and solubility of Tm³⁺in glass matrix were improved,and the fluorescence emission of Tm³⁺in 2.0?m band was enhanced.The doping concentration of Tm³⁺reaches 5 mol.%(9.8×10²⁰ ions/cm³),which is the highest in the reported Tm³⁺doped glass and fiber.(2)The high Tm³⁺BGG glass was co-doped with Ho³⁺to explore the wide band luminescence properties at 2.0?m.And the FWHM of the fluorescence emission at 2.0?m band reached 384 nm by optimizing the composition of glass,indicating that the Tm³⁺/Ho³⁺co-doped multi-component germanate glass can be used to fabricate 2.0?m band gain fiber with high gainper unit length and ultra-wideband.(3)Through optimizing the water removal process and melting process of BGG glass,a bulk highly Tm³⁺doped BGG laser glass with low hydroxyl(OH^-absorption coefficient is as low as 0.09 cm^-1)content was prepared,and the maximum gain coefficient at 2.0?m band was6.31 cm^-1.A bulk BGG cladding glass matching the physical and chemical properties of the core glass was also prepared.According to the requirements of single-mode fiber,the size of fiber preform rod was designed,and the drawing technology and technology were optimized.Finally,the highly Tm³⁺-doped BGG glass single-mode optical fiber was prepared,which provides the key material for the fiber laser at 2.0?m band.