Research On Controllable Synthesis And Luminescence Tuning Of Lanthanide-doped Calcium Fluoride Nanocrystals

Diode pumped nanoparticle gas laser?DPNGL?has the advantage of both solid laser and gas laser,featured for wide-band pumping,efficient thermal management by flowing the gaining medium,electrically driven compact system and so on.This concept is promising in dealing with the ultimate difficulty of thermal management in high power laser systems and it has become a new approach for the megawatt-class laser with all-electric drive of next generation.Lanthanide doped nanoparticles have the potential to become an ideal gain medium for diode pumped nanoparticle gas lasers due to their low quantum defect,large absorption cross section,long fluorescence lifetime,and artificially adjustable optical properties.Among all the matrix materials,calcium fluoride matrix is a frequently-used matrix material for lanthanide doped nanocrystals because of its low refractive index,small scattering,wide transmission range and low phonon energy.It is of great significance to study the controllable synthesis and luminescence tuning of lanthanide doped calcium fluoride nanomaterials at nanoscale for the artificial design of gain media in nanoparticle gas lasers.Therefore,this dissertation mainly employs hydrothermal method to synthesize lanthanide doped calcium fluoride nanomaterials,and explores the effective method to control its luminescent properties.1.The potential and advantages of lanthanide doped nanocrystals as gain medium for nanoparticle gas lasers are described.The spectral properties of rare earth ions are summarized based on its electronic configuration.The research status of lanthanide doped nanocrystals is presented and the advantages of selecting calcium fluoride as matrix material are illustrated.2.As the basis of the research on the properties of nanoparticles,the main experimental methods and theories of the subject are introduced.The chemical reagents and instruments used in the preparation of materials are introduced.The operation steps of hydrothermal method and high temperature thermal decomposition method in the synthesis of nanoparticles are described in detail.The common characterization methods such as scanning electron microscopy analysis and energy spectrum analysis are summarized.3.Hydrophilic and monodisperse Mn²⁺doped CaF₂:Yb³⁺/Ho³⁺microspheres were prepared by hydrothermal method.The tuning effect of Mn²⁺doping on Yb³⁺/Ho³⁺up-conversion luminescence system was studied in detail.Under the excitation of 980 nm CW laser,with the increase of Mn²⁺doping concentration,the green-yellow-red up-conversion fluorescence was achieved and the red emission of Ho³⁺was greatly enhanced.The measurement of the fluorescence lifetime of Ho³⁺and the power dependence of fluorescence intensity directly prove the proposed energy transfer process between Ho³⁺and Mn²⁺.4.CaF₂:Yb³⁺/Er³⁺/Na⁺tri-doped upconversion nanoparticles were prepared by hydrothermal method with EDTA as chelating agent.The influence of Na⁺doping in CaF₂:Yb³⁺/Er³⁺system was studied by 980 nm CW laser excitation.By changing the doping concentration of Na⁺,the lattice environment around the lanthanide ions was changed,and the luminescence of Er³⁺was enhanced,which provided an effective solution to improve the fluorescence intensity of CaF₂ matrix nanomaterials.