The Study On The Luminescent Characteristics And Sensitization Mechanism Of Er³⁺/Pr³⁺,Yb³⁺/Pr³⁺ions Co-Doped LIYF₄Single Crystals

Yttrium lithium fluoride single crystal （LiYF₄or YLF） is a relatively new hostmaterial, which have good spectroscopy and laser performance. And LiYF₄single crystalis suitable for the introduction of trivalent rare-earth ions, which serve as substitutes for theY³⁺ion. Doping with different activator ions may emit various wavelengths laser at roomtemperature. In this thesis, Pr³⁺/Yb³⁺ions co-doped and Er³⁺/Pr³⁺ions co-doped LiYF₄single crystals were grown by Bridgman method successfully. XRD, absorption spectra,excitation and emission were measured. And the luminescent properties and energytransfer mechanisms of various samples were investigated by using Inokuti-Hirayamamodel.In chapter one, we briefly introduced laser crystals, especially fluoride crystals. Theproperties of Yttrium lithium fluoride single crystal have been introduced in detail. Thetechniques used in growing crystals, basics of energy transfer between rare-earth ions, thecharacteristics of Praseodymium ion, quantum cutting concepts and effectivesegregation coefficient of rare earth ions in LiYF₄crystals also have beenpresented.In chapter two, X-ray diffraction, photoluminescence excitation and emission spectraand decay curves are measured to investigate the structural and luminescent properties ofthe crystals grown by Bridgman method. An efficient near-infrared quantum cuttingdownconversion from the crystals was observed. Decay curve fitting using a modifiedInokuti-Hirayama expression indicates dipole-dipole energy transfer from to Pr³⁺to Yb³⁺,which is consistent with the cross-relaxation scheme.In chapter three, the emission characteristics and energy transfer of various parts ofcrystal upon excitation of a980nm laser diode are investigated. Population inversionsbetween4I13/2and4I11/2levels have been achieved successfully. The energy transfer processes are studied based on the I-H model, and the interaction between Er³⁺and Pr³⁺isconfirmed to be electric dipole-dipole.Finally, we draw a conclusion of our research and the outlook for future research.