Study On The Fiber Laser And Magneto-optical Properties Of Rare Earth Ions Doped Yttrium Aluminum Silicate Glasses

The emergence of low-loss silica optical fibers has greatly changed our lives.As an ideal optical wave-guide,they have been applied in many fields such as optical communication,medical treatment,fiber laser,environmental sensing,and precision processing,etc.After decades of development,the transmission loss of commercial silica optical fibers has approached to the theoretical minimum limit and a complete upstream and downstream industry have been established.However,the transmission window of silica material mainly locates in the near-infrared region,which imposing challenge for applications in mid-infrared regions.Besides,the optical non-linearity of silica is too low for nonlinear applications,which limits the development of fiber-based nonlinear optical devices.To meet the diversified requirements of fiber performance demanded by those developing specific applications,the most fundamental solution is to develop special optical fibers featuring with advanced properties.During the past three decades,due to the success of advanced optical fiber drawing methods such as the rod-in-tube method,molten-core method and thermal drawing method,a large number of special optical fibers have been studied and reported,providing important optional solutions for specific applications.Generally,a more complex fiber cross-section geometry or an unique core-cladding composition are the basic conditions for those special optical fibers to achieve special performance.In the past two decades,a typical multi-component glass fiber,the yttrium aluminosilicate(YAS)glass fiber,has been widely studied because of its flexible rare earth doping mechanism,good physical and chemical stability,good optical properties,reliable and convenient preparation,and compatibility with silica fiber network etc.In this paper,based on the full investigation of the relevant literature about the molten-core method and the preparation of YAS optical fiber,a series of work are conducted aiming for expanding the application potential of YAS fiber and exploring its formation mechanism.The research contents include the formation mechanism of the YAS fiber,the wave-guide structure characteristics of the YAS fiber,the laser and magneto-optical properties of the rare earth ion doped YAS fiber system.Our work are helpful to understand the preparation of this core-clad heterogeneous fiber from the bottom of the preparation process and realize the regulation of the fiber performance.The specific research contents and results include:(1)Based on the molten core method,different condensed materials(powder,Y₃Al₅O₁₂(YAG)crystal,YAG ceramic)were used to prepare the YAS fibers and the performance of obtained fibers are compared.The experimental results show that YAG ceramics sintered by high temperature solid-phase method(the density equal to 60%of single crystal)can be used as a reliable precursor material to prepare YAS fiber with different rare earth doping mechanism.Besides,a comparative experiment with was designed to study the effect of different initial traction force during the fiber drawing process.The results show that the formation mechanism of YAS fiber includes the"persistent"element diffusion process developing with time and the unique short-acting"mutation"mechanism based on the stress extrusion of heterogeneous interface.The discussion of the latter can be applied to most of the cases that fibers are prepared by the molten core method from a heterogeneous core-cladding materials preform.By adopting reasonable fiber drawing parameters,the wave-guide structure parameters of the prepared YAS fiber can be theoretically regulatable.(2)The waveguide structure and spectral characteristics of Nd:YAS fiber drawn from 1at%Nd:YAG crystal are studied.From the distribution of the elements,stress and refractive index of the cross-section of the obtained YAS fiber,a"tree ring"type structure model is proposed.Based on the prepared Nd:YAS fiber,an all fiber laser resonator was constructed,the fiber laser output around 1064 nm was realized and the performance parameters of the fiber laser are characterized.In addition,we use 10 at%Nd:YAG ceramics to fabricate YAS fiber with high Nd³⁺content,single frequency laser output was realized in a 1.7 cm-long distributed Bragg reflection(DBR)cavity.(3)Tm:YAG ceramics with different doping concentrations were prepared by high temperature solid-phase method and then were used to fabricate Tm:YAS fibers.The effects of Tm³⁺concentration on the fluorescence properties and fluorescence lifetime of Tm:YAG ceramic samples were compared and analyzed.The 1950 nm fiber laser was realized by a all fiber laser resonator based on the obtained Tm:YAS fiber.This work presents the first report on the 2?m band YAS fiber laser,it is also proved that the YAS fibers prepared by molten core method are able to realize flexible rare earth ions(in the concentration and type)doping,which indicates the universal potential of YAS fiber for rare earth ions related application fields.(4)Highly doped Yb:YAS fiber was prepared from a 10 at%Yb:YAG transparent ceramic,the fluorescence property of the Yb:YAS fiber was characterized.A 4.4 cm long fiber amplifier was built to characterize the unit length gain performance of the prepared Yb:YAS fiber and Yb:YAS single frequency fiber laser output was realized based on a DBR short cavity.This work proved for the first time that the YAS fiber can be used as a stable multi-component glass fiber for single frequency laser.(5)As an exploration in another rare earth ions related potential application—the magneto-optical applications,we prepared a series of highly doped TAS and TASB glasses by the melt-quenching method.The effects of B₂O₃on the Faraday rotation angle,refractive index,thermal properties and micro-structure of glass samples were analyzed.The results show that the prepared glasses possess excellent comprehensive properties.Considering the composition of the prepared TAS and TASB glasses were referred to the composition of our realized YAS fibers,the related results are helpful to promote the development of magneto-optical fibers based on the YAS glass system.