Composition Design Of Fluoride Glass Doped With Rare-Earth And Study On The 3μm Mid-Infrared Emission Properties

Abstract:In the 1960s,Maiman in the United States made the world’s first ruby laser.In just a few decades,laser technology has been rapidly applied to all aspects of modern industry,agriculture,medicine,communication,national defense and science technology.The mid-infrared～3μm laser is located in the absorption peak position of water molecules and many important atmospheric molecules,which has important application potential in the fields of medical surgery and environmental monitoring.The development of coherent sources available in this region will greatly promote the progress of civilization.Fiber laser is one of the most popular laser technologies because of its advantages of adjustable energy and high beam quality.How to optimize the luminescent efficiency and thermal stability of laser gain medium by adjusting the fluorescence transition of rare earth ions and reasonable glass composition design is the core issue of developing mid-infrared fiber laser devices.Er³⁺,Dy³⁺and Ho³⁺ions have rich laser energy levels,which enables them to achieve multiple wavelength output.They are the common rare earth ions emitting in～3μm band.However,these luminescence center ions generally have the problem of low mid-infrared transition efficiency.At present,the energy transfer process between ions is regarded as the most direct and effective way to solve this problem.As for the mid-infrared matrix materials,Novel heavy metal oxides,fluorides and chalcogenide glasses have been widely studied for their low phonon energy and excellent optical properties.The fluoride glass represented by ZBLAN has wide transmission range in the mid-infrared band,low hydroxyl content and stable luminescent performance,so it is the preferred material for the～3μm and above band emission.However,it is easy to be crystallized in large-scale production and has poor thermal stability,which seriously hinders its application in high-power fiber laser devices.In this paper,some network modifiers were added to improve the components of fluoroaluminate（AMCSBY）and fluorozirconate（ZBYA）glasses respectively,in order to obtain a new type of fluoride glass component with excellent thermodynamic properties.On this basis,the luminescence properties of the mid-infrared activated ions in the glass matrix,the sensitization mechanism of the sensitizing ions to the activated ions and the energy transfer between the activated ions were explored respectively.This thesis can be divided into five chapters.The first chapter of the thesis first outlines the significance of mid-infrared～3μm band lasers and the current means of obtaining～3μm laser light sources,emphasizes the advantages of fiber lasers,and reviews the latest research progress of～3μm band high power fiber lasers.Secondly,the problems of rare earth ions and glass matrix materials involved in the study of～3μm fiber laser gain medium are described separately,the latest research progress is analyzed,and the remaining problems and challenges are clarified.Finally,the research purpose of this topic is pointed out,and the experimental scheme and research content are introduced.The second chapter of the thesis introduces the preparation of fluoride glass samples,resesrch methods,performance testing methods,calculation and analysis methods of spectral theoretical parameters,etc.In the third chapter,the glass matrix with better thermal stability was obtained by Al（PO₃）₃network modification of the classic fluoroaluminate glass（AMCSBY）component.DSC curve test showed that the thermodynamic properties of this new glass matrix can effectively support it as a mid-infrared gain medium.Then the sensitization mechanism of Er³⁺:2.7μm fluorescence by different sensitizing ions in glass matrix was studied.The fluorescence spectra and fluorescence decay curves show that different sensitizing ions have different effects on the fluorescence intensity of Er³⁺:2.7μm.among all sensitizing ions,Pr³⁺,Tm³⁺,Nd³⁺and Ho³⁺have quenching effect on Er³⁺:⁴I_13/2level,and the quenching effect of Pr³⁺is the strongest.On the other hand,Yb³⁺ion can greatly improve the absorption efficiency of the system for the pump source,so it can enhance the emission intensity of each band of the system,but the"bottleneck effect"of Er³⁺ion can’t be eliminated directly by Yb³⁺ion co-doping.Finally,the sensitization mechanism of each sensitizing ion was studied in detail.In the fourth chapter of the dissertation,the fluorozirconate glass（ZBYA）was modified with different proportions of Zn F₂network modifiers,and a new type of pure fluoride glass substrate（ZZBYA）with good thermal stability was explored.The DSC curve,transmission spectrum and Raman spectrum were used to characterize its thermodynamics,light transmission,and structural information.Subsequently,the radiation and energy transfer mechanism of the dual mid-infrared luminescent centers in the new fluorozirconate glass matrix were studied.In the Er³⁺/Ho³⁺co-doped system,fluorescence spectra and lifetime tests show that Er³⁺can absorb the energy of the 980nm pump source and transfer part of it to Ho³⁺.The Ho³⁺ion effectively quenches the ⁴I_13/2energy level but has a small effect on the ⁴I_11/2energy level corresponding to the Er³⁺:2.7μm emission.Therefore,for the Er³⁺:2.7μm lasing operation,the Ho³⁺ion can be used as a sensitizing ion.In addition,the effective linewidth of the～3μm emission spectrum increases with the Er³⁺concentration in the Er³⁺/Ho³⁺co-doped samples.Similarly,Dy³⁺/Er³⁺co-doped samples can also obtain broadband emission consisting of Dy³⁺:⁶H_13/2→⁶H_15/2and Er³⁺:⁴I_11/2→⁴I_13/2transitions under 980nm excitation.The above studies show that these two Co-doped systems have potential applications in the field of broadband tunable laser light sources.The difference is that under the excitation of 808nm,it was found that Er³⁺:⁴I_13/2→Dy³⁺:⁶H_11/2has a very high energy transfer efficiency（96.1%）,which means that Er³⁺can be used as an effective sensitizing ion for Dy³⁺ions.Further experiments show that 1.5mol%Er³⁺is the optimal sensitization concentration of 1mol%Dy³⁺ions in～3μm emission.The last chapter is the concluding part of this thesis,which summarizes the experimental results of the full text,points out the deficiencies,innovations and plans the future improvements of this research topic.