The Growth And Study On Luminescent Properties Of Tm³⁺,Er³⁺/Tm³⁺,Er³⁺/Nd³⁺ Co-doped LiYF₄Single Crystals

Yttrium lithium fluoride single crystal (LiYF4) is a relatively new host material, which havegood performance of thermal, mechanical, chemical stability, low phonon energy and hightransmittance. The Y3+in LiYF4single crystal has the similar ionic radius to many rare earth ions,so the trivalent rare earth ions can be easily replaced the Y3+in LiYF4single crystal. Er3+ions is anideal mid-infrared emitting ions, the luminescent center as2.7μm, corresponding to the4I11/2â†'4I13/2level transition, but the fluorescence lifetime of4I13/2is greater than that of the4I11/2level andtherefore it is difficult to obtain ideal mid-infrared laser. In order to enhanced the2.7μm intensityof Er3+, the Tm3+, Nd3+ions are introduced to the Er3+to reduce the4I13/2level of energy effectively.This paper used Bridgman method to grow the Tm3+, Er3+/Tm3+, Er3+/Nd3+co-doped LiYF4singlecrystals，and the spectra properties were studied to understand the luminescent properties.In chapter one, we briefly introduced laser crystals, especially fluoride crystals. The propertiesof yttrium lithium fluoride single crystal have been introduced in detail. The techniques used ingrowing crystals, the characteristics of doped rare earth ions, effective segregation coefficient ofrare earth ions in LiYF4crystals and the difficulties in crystals growth also have been presented.In chapter two, we carry a study on the luminescent properties of the Tm3+:LiYF4single crystal.The absorption and emission cross sections around1800nm are calculated. Results indicate thatthe Tm3+:LiYF4single crystal have potential applications in2μm solid lasers.In chapter three, the process of the Er3+/Tm3+:LiYF4single crystals growth was described indetail. The luminescent properties of the Er3+doped and Er3+/Tm3+co-doped are analysised and theoptimum concentration of Er3+and Tm3+for the2.7μm is also got. The mechanism of the energy transfer between Er3+and Tm3+is studied abundantly through the lifetimes.In chapter four, a study about the luminescent properties of Er3+/Nd3+:LiYF4single crystalsunder800nm excitation were demonstrated. The researches are carried on the absorption spectra,IR transmittance spectra, fluorescence spectra. We obtain the optimum concentration of Er3+andNd3+for the2.7μm, and the reasons for the fluorescence quenching are discussed. The energytransfer process between Er3+and Nd3+is discussed emphatically. The energy transfer efficienciesfrom Er3+to Nd3+and from Nd3+to Er3+are all calculated. The energy transfer processes arestudied based on the I-H model, and the interaction between Er3+and Nd3+is confirmed to beelectric dipole-dipole.Finally, we draw a conclusion of our research and the outlook for future research.