Study On Defect State Regulation Of Luminescence Materials Via Thermal Assitance And Its Application In Optical Storage

As an ideal candidate material for the next generation of high-density optical storage media,defect-state optical storage materials have attracted continuous attention of researchers.However,such materials still have shortcomings such as long-persistent luminescence（LPL）interference of shallow trap,low self-storage capacity,and short writing wavelength,which limit their practical application.This dissertation intends to solve the above problems by introducing the thermal field to cooperate with the light field writing（thermally assisted strategy）.High-density long-persistence luminescence materials with deep traps and photo-stimulated luminescence materials dominated by deep traps are selected as the research objects.Through thermally assisted elimination of LPL interference of shallow trap and enhancement of long wavelength photon writing capacity,the ideal properties of these two-representative defect-state optical storage materials in trap distribution,filling capacity and writing wavelength are realized,which promotes the practical process of their optical storage applications.The main research contents and results are as follows:1.The high-density LPL material Sr Al₂O₄:Eu²⁺,Dy³⁺containing deep traps were prepared by high-temperature solid state method.The purpose is to eliminate the LPL interference of shallow traps by thermal assistance,and to study the thermal assisted optical storage properties of the material excited by different wavelengths and power light in detail.It is found that under photothermal cooperative writing,the central depth of trap filling can be significantly deepened with the increase of auxiliary temperature.Although there will be shallow trap residual filling,it can be effectively removed by reducing the excitation power.and the shallow trap can be removed more effectively by reducing the excitation power,indicating that the thermal auxiliary strategy has the potential to promote the actual optical storage applictions of LPL type defect state optical storage materials.At the same time,it is also found that there is an increase in the filling capacity of thermal assisted traps（thermal increment effect）in the excitation of high-energy photons,while the excitation of low-energy photons is an abnormal thermal assistant phenomenon of thermal attenuation.On this basis,a new thermal increment mechanism of thermal energy enhancing the excitation efficiency of stimulated luminescence or reducing the filling rate of excited light de trap is proposed.Then,a high-density LPL material Sr Ga₂Si₂O₈:Mn²⁺with deep traps and multiple excitation levels is designed and prepared in order to solve the problem of shallow trap filling residue of high-density LPL material through thermal assisted tunneling effect writing strategy.The results show that in the process of directly filling deep traps through tunneling channels,the trap filling depth will deepen with the increase of thermal auxiliary temperature,and accompanied by thermal increment,which shows that this strategy has the potential to realize optical storage without LPL interference.2.In order to better avoid the interference of shallow traps,this part takes the photo-stimulated luminescence materials dominated by deep traps as the research object to study the thermal-assisted optical storage performances.In the two materials Y₃Ga₂Al₃O₁₂:Ce³⁺-Cr³⁺and Y₂Ge O₅:Pr³⁺,it is found that the thermal increment capacity of long wavelength excitation with spin permission and outer electron transition(Ce³⁺,4f-5d transition)is significantly higher than that with parity prohibition and inner electron transition(Pr³⁺,4f-4f transition).Furthermore,the thermal assisted optical storage performances of Ba Si₂O₅:Eu²⁺system with spin-allowed outer electron transitions and deeper trap distribution is explored,and a better thermal increment effect is obtained.Meanwhile,by constructing the energy band structure of the Ba Si₂O₅:Eu²⁺system,it is found that the thermal increment energy levels have entered the conduction band,which shows that the thermal increment mechanism is not that thermal ionization helps more excited electrons enter the conduction band,but a thermal increment mechanism similar to Sr Al₂O₄:Eu²⁺,Dy³⁺system.4.Based on the excellent thermal increment performance of Ba Si₂O₅:Eu²⁺and its co-doped system,three thermally assisted novel optical storage modes are constructed and demonstrated.Firstly,by further combining the properties of Yb³⁺that can significantly absorb 980 nm photons into heat,Ba Si₂O₅:Eu²⁺,Er³⁺,Yb³⁺material was designed,and the high-temperature stable storage properties with point heating under980 nm laser assisted writing was obtained.Then,the Na YF₄:Yb³⁺,Tm³⁺/Ba Si₂O₅:Eu²⁺,Nd³⁺composite material system was designed to convert near-infrared light to blue and violet light,and realized the optical storage mode of 980 nm laser writing signal under thermal assistance.Finally,by using the characteristics that the storage capacity of Ba Si₂O₅:Eu²⁺,Pr³⁺and Sr Ga₂Si₂O₈:Mn²⁺,Yb³⁺materials is regulated by thermal assistance and excitation power respectively,Ba Si₂O₅:Eu²⁺,Pr³⁺/Sr Ga₂Si₂O₈:Mn²⁺,Yb³⁺material system was designed,and the intensity and wavelength co-multiplexing optical storage display based on defect-state optical storage materials was realized.