Micro-nano Scale Regulation Of Silicate Glass Structure And Its Influence On Mid-infrared Emission Properties

Due to the vast application prospect of mid-infrare Fiber lasers in fields of medical science,atmospheric monitoring,precision machining,environment protection and military affairs,improving the spectroscopic performance of mid-infrared photonic glass matrix has been the key issue and researching focus in recent years.To realize such improvement,traditional approaches include continuously chemical doping or changing the composition of materials.However,the extrinsic effects originated from the large-scale transformation of host structure,including chemical inhomogeneity and defects,are irreversible thereby unlikely for researchers to understand the detailed kinetic process of the light amplification effect.In addition,it is also very necessary to manipulate the glassy structure within nanoscale.The main purpose of this dissertation is to adjust the glass structure at different scales,to improve the mid-infrared fluorescence performance and provide theoretical and experimental basis for obtaining excellent mid-infrared laser glass materials.The dissertation includes the following six chapters.Chapter 1 is the literature review.It mainly introduces the origin of mid-infrared laser and the related applications,and then compares several rare earth ions and glass matrix,as well as the principle and methods for tuning the glassy structure within nanoscale.Furthermore,we review the glass ceramic materials that are applicable for such methods and put forward the main research contents in this paper.Chapter 2 introduces the experiment methods and the theory calculations,which includes the preparation procedures of glass samples,the measurements of the main properties?physicochemical,structural,thermal,electrical,spectroscopic properties?,the calculation of J-O paramaters and the theory analysis.Chapter 3 presents the macro-scale method to manipulate the glassy structure,which is mainly focused on the change of the content of glass former and modifier.We investigate the related impact of such method on the glassy structure as well as the physical and chemical properties.The results show that in the lead silicate glass system where the mid-infrared luminescence intensity has reached to the saturation,with the continouly addition of modifier?Pb?,the chain structure in the glass will change,that is,the Pb ions will depolymerize the Si-O bonds that are relatively too long and re-connect with the broken Si-O short chains and form Si-O-Pb chain structure.After these series of variations,the overall macro structure of the glass becomes comparatively looser without breaking the mechanical and thermal properties of the glass.Therefore,more rare earth ions can enter the glass network thanks to the looser structure,so that the 2.0?m luminescence intensity is enhanced,and the quenching threshold is increased by 60%.Chapter 4 presents the nanoscale method to manipulate the glassy structure,which is realized through the doping of alkali metal ion.The Li⁺ions are introduced into the crystal lattice as the alkali metal ion,and their influence on the ligand environment around RE ions is analyzed.Li⁺ions will not break the chain structure of glassy phase,meanwhile,the crystalline phase will not be altered as well.The only change is the local environment of RE ions inside the crystal lattice,therefore,the nanoscale adjustment of glassy structure can be achieved.When Li⁺ions are introduced into Er³⁺:Ba_0.27Sr_0.75Nb₂O_5.78 glass ceramic system,although the inner Er-O bonds will not be broken,they will still suffer from slight distortion due to the Li⁺ions,so that the asymmetry around RE ions is enhanced.As a result,in this system,the 1.55?m mid-infrared emission is enhanced by 1.4 folds.The chapter 5 presents another efficient method to manipulate the glass structure within nanoscale,which is realized by electric polarization.This method is helpful to investigate the dynamic relationship between crystal field and the light excitation process.Owing to the unique structure of ferroelectric phase,polarization will emerge inside the cubic cell.To be exact,the anion and cation inside the oxygen octahedron will shift and cause the slight distortion of lattice,which will impact the luminescence of RE ions in many aspects,including the the surrounding electrostatic field,environmental asymmetry,and lattice phonon energy.Several ferroelectric glass ceramic systems are prepared to implement this method,and the mid-infrared luminescence properties are all undergoing obvious enhancement.In Er³⁺:Ba_0.27Sr_0.75Nb₂O_5.78 system,the 1.55?m luminescence is enhanced by 4.93 folds;in Er³⁺:LiNbO₃ system,the 1.55?m luminescence is enhanced by 6.45 folds;in Tm³⁺:LiNbO₃ system,the 1.85?m luminescence is enhanced by 3.45 folds;in Er³⁺/Dy³⁺:Bi₄Ti₃O₁₂ system,the 2.85?m luminescence is enhanced by 2.13 folds.Apart from the change of luminescence property originated from electric polarization,the effect of RE ions on the energy-storage properties also worth researching.In Er³⁺/Dy³⁺:Bi₄Ti₃O₁₂ system,the energy density and energy-storage performance are both promoted by RE doping.The chapter 6 is the conclusion of the whole dissertation,in which the experimental results are summarized and the shortcomings are also pointed out.