The Study Of Rare Earth Ions Activated CaYAlO₄ Visible Laser Crystal

Visible laser has a wide range of applications in our daily life,such as laser headlamp,medicine,projector and data storage.In addition,it also has some important potential in the new generation of display technology,microscope,visible light communication and scientific research.With the development of commercial blue laser diode（LD）,direct pumping of rare earth ion doped laser crystal to obtain visible laser has attracted more and more attention.At present,the researchs of visible rare earth ions mainly focuses on Sm³⁺,Dy³⁺,Tb³⁺,Pr³⁺and so on.The spectral characteristics of rare earth ions are strongly dependent on the local lattice structure,which need somematrix crystalswith high degree of structural disorder.CaYAlO₄with disordered structure is an excellent matrix material,which has the advantages of good physical and chemical properties,low phonon energy,high light damage threshold,etc.On this basis,the growth and spectra of Sm³⁺,Dy³⁺,Tb³⁺doped CaYAlO₄ visible light laser crystal were studied in this thesis.The main work is as follows:（1）2at%Sm³⁺doped CaYAlO₄ crystal was grown by the Czochralski method.The room temperature polarizated absorption spectra,polarizated fluorescence spectra,fluorescence decay curve,as well as the variable temperature spectra were measured.Based on the Judd-Offelt（J-O）theory,the spectral characteristics are studied and a series of spectral parameters were calculated.Theσandπpolarization absorption cross sections at 408 nm are4.09×10^-20 cm² and 2.43×10^-20 cm²,respectively.The intensity parameters of J-O are2.7×10^-20 cm²,4.15×10^-20 cm² and 4.12×10^-20 cm²,respectively.The cross-section ofπpolarization at the emission peak（601 nm）is 10.06×10^-22 cm².The fluorescence lifetime of⁴G_5/2 energy level is 0.83 ms and the quantum efficiency is 58.5%.The results show that Sm³⁺:CaYAlO₄crystal is an excellent yellow laser crystal.（2）In order to optimize the spectral properties of 2at%Dy³⁺:CaYAlO₄ crystal which was grown in the early stage of our team,co-doped with deactivation ion Tb³⁺,2at%Dy³⁺/0.5at%Tb³⁺:CaYAlO₄ crystals were grown.and a series of spectral studies were carried out.The results show that the co-doped crystal has strong absorption in 300-500 nm band.Due to the deactivation of Tb³⁺,the absorption cross section of the crystal at 453 nm does not decrease,but the emission cross section at 582 nm is slightly strengthened.Due to the increase of Dy³⁺doping concentration lead to the fluorescence lifetime of the upper energy level ⁴F_9/2 increases.Meanwhile,the fluorescence lifetime of ⁶H_13/2 is 0.023 ms,and the energy transfer efficiency of Dy³⁺and Tb³⁺is 39.47%,which is beneficial to realize particle number inversion and the operation of laser.（3）10at%Tb³⁺:CaYAlO₄ and 10at%Tb³⁺/0.6at%Pr³⁺:CaYAlO₄ crystals were grown.The polarizated absorption spectra,polarizated fluorescence spectra,fluorescence decay curve of the crystals were measured at room temperature.A series of spectral parameters were calculated based on J-O theory.The effect of sensitized ion Pr³⁺on fluorescence emission intensity and fluorescence lifetime,as well as the energy transfer process of Tb³⁺and Pr³⁺were analyzed.The results show that Tb³⁺:CaYAlO₄ crystal has relatively strong absorption at 487 nm,which is suitable for Al Ga As LD pumping.The visual range emission bands located around 546 nm,587 nm has a large emission cross section.After sensitizated by Pr³⁺,the absorption of Tb³⁺/Pr³⁺:CaYAlO₄ crystal is enhanced,but the emissionin visible band is weakened.Due to the high concentration of Tb³⁺,the energy of Tb³⁺is transferred to Pr³⁺,the emission spectra intensity,emission cross-section and fluorescence lifetime of Tb³⁺were decreased.Different concentrations of Pr³⁺and 10at%Tb³⁺:CaYAlO₄ crystal fibers were grown by micro-down method.Their fluorescence spectral intensity was investigated.It was found that the fluorescence intensity decreased with the increase of Pr³⁺concentration,therefore the effective absorption of Tb³⁺to LD pump source could be enhanced by co-doping Pr³⁺.The visible emission of Tb³⁺cannot be enhanced.The variable temperature fluorescence spectra of Tb³⁺:CaYAlO₄ and Tb³⁺/Pr³⁺:CaYAlO₄ crystals were measured.The results show that the fluorescence spectra of Tb³⁺/Pr³⁺:CaYAlO₄ crystals have good thermal stability.These results indicate that Sm³⁺:CaYAlO₄,Dy³⁺/Tb³⁺:CaYAlO₄,Tb³⁺:CaYAlO₄ and Tb³⁺/Pr³⁺:CaYAlO₄ crystals are expected to be applied to the visible light laser system pumped by commercial blue LD.