The Structure And Upconversion Luminescence Properties Of Lithium Ni-obate Crystals Co-doped With Scandium Ions And Erbium Ions

With the advent of the laser, people started to focus on researching and exploratingthe laser materials. Upconversion luminescence materials doped rare earth have greatpotential applications in many new areas. Among these materials, rare earth doped lithiumniobate crystal shows outstanding features due to both its good nonlinear opticalproperties and ecellent spectral properties of rare earth ions. With the excitation of a singlepump light, luminescence from the near infrared to visible light can be achieved in rareearth doped upconversion luminescence materials. Thus, it is significantly important toinvestigate the rare earth doped upconversion luminescence materials.In this thesis, Sc/Er-codoped with different concentrations anti-photodamage ionsSc3+in LiNbO3crystals have been grown by the Czochralski method. The InfraredTransmission spectroscopy (IR), Ultraviolet and Visible Absorption spectroscopy(UV-VIS) and Upconversion Luminescence spectroscopy (UC) of Sc:Er:LiNbO3crystalswere investigated. The factors of the spectroscopy characteristics and UC properties of theEr:LiNbO3changing with the concentration of the doping ions were analysedsystematically, providing experimental basis and theoretical guidance for developinghigh-quality upconversion luminescence materials.Firstly, the structure and defect structure of the pure congruent LiNbO3crystal wereanalysed. The absorption peaks position and the corresponding levels of Er3+wereobtained from the IR spectroscopy and UV-VIS absorption spectroscopy in theSc:Er:LiNbO3crystal samples. The location of the doped ions was analysed inside theLiNbO3crystal through the shifting of the OH-absorption peak and the UV absorptionedge.Secondly, the upconversion fluorescence spectrums of the three Sc:Er:LiNbO3samples shows much evidently stronger intensity excited by the femtosecond lasercompared with that by conventional lasers. Meanwhile, the upconversion fluorescencespectrum intensity increases with the increase of the Sc-doping concentration when theconcentration is under the threshold concentration, however, the intensity would be suppressed when the concentration is above the threshold concentration. In addition, thereis a second harmonic at400nm excited by800nm femtosecond.Finally, the factors that cause the changes of the upconversion fluorescence spectrumintensity were analysed in combination with spectroscopy theory and the test results; Themechanism of400nm was analyzed detailedly and the factors causing the changes of itsintensity were discussed.