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The Structure And Properties Research On Er:YbVO4 Crystal

Posted on:2008-09-08Degree:MasterType:Thesis
Country:ChinaCandidate:W L GaoFull Text:PDF
GTID:2178360212994707Subject:Condensed matter physics
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Because it combines semiconductor with solid, the laser diode pump solid-state laser(DPSSL) possess the merits of both semiconductor and solid.DPSSL has the properties of high pumping efficiency, stable output power and all solid state. DPSSL have found many important application fields material processing.control and guide,medicine,optical communications ,laser display and laser nuclear fusion.So far as DPSSL is concerned, laser materials are important and they are the key factor for designing all solid-state lasers for DPSSL and decide the properties of lasers. Er:YbVO4 crystal is also a laser crystal with excellent laser properties.Due to the erbium (Er) ion 1.5μm infrared emitting light good security and eye-safe, in the optical information, the optical communication, the medicine health and the national defense military , it has the very big potential application. The Yb ion has the extremely simple energy level structure (an excited state) and the energy gap is approximately 10000cm-1, which is ideally suited for LD pumping near 976nm (commercialized),and it efficiently sensitizes the Er ion, thus it greatly reduces the doping density of the Er ion,and effectively reduces reabsorption at 1.5μm and avoids the quenching effect.Therefore we grew the Er:YbVO4 crystal by using the Czochralski method. The Er:YbVO4 crystal has the broad absorption band and high thermal conductivities. It is suitable for the high power laser application which is pumped by the laser diode. In a word, in this thesis, our work can be summarized by follows: 1. The YbVO4 and Er:YbVO4 crystals were grown by using the Czochralski method. The YbVO4 and Er:YbVO4 crystals are both the zircon crystals.The point group is 4/mmm, the space group is I41/amd.2.Based on the space group theory, the lattice vibration modes of YbVO4 and Er:YbVO4 are predicted.The YbVO4 and Er:YbVO4 crystals has the same structure .It comprise 4 units per cell,has 24 atoms and 72 lattice vibration modes.They were: Γ=5A1g+2A2g+2A1u+7A2u+7B1g+2B2g+2B1u+5B2u+10Eg+10Eu There are 72 modes, which equal to the movement degrees of freedom 72 of the 24 atoms. From the character table of the point group 4mmm, we know that 1A2u and 1Eu are acoustical modes, 5A1g, 7B1g and 2B2g are optical mode, 10Eg are dual degenerate mode,the others are dual degenerate optical modes.Theoretically,we can observe 32 active optical modes at the most from the crystal ,they areΓVib= 5A1g+7B1g+2B2g+10Egwe determine the Raman scattering spectra of YbVO4 and Er:YbVO4 at room temperature by JASCONRS-1000DT micro Raman spectrophotometer, excellent agreement has been achieved between vibrational frequencies predicted by the theory and those observed in experiment. And we give some explain for that of Er:YbVO4 crystal. 3. The thermal properties of Er:YbVO4 single crystal were systemically studied, the specific heat was measured by the method of differential scanning calorimetry ,which value was 0.41Jg-1 K-1 at the temperature of 330K. The thermal expansion of Er:YbVO4 single crystal was measured by using a thermal dilatometer and the average linear thermal expansion coefficient for all three crystallographic directions were calculated in the temperature range from 298.15K to 900K , which values areαa= 4.244×10-6/k, αb=4.07834×10-6/k, αc=7.0×10-6 /k. We analysis the anisotropic property of Er:YbVO4 single crystal with structure feature of the crystal.we measured the thermal diffusion coefficient of Er:YbVO4 single crystal and calculated the thermal conductivities of the crystal. At 303.15K, the thermal diffusion coefficients are 1.573mm2/s and1.956mm2/s along the Er:YbVO4 single crystal [100] and [001] directions, the thermal conductivities are 3.87W/m·Kand 4.81W/m·K,correspondingly. The influences of these thermal properties on optical applications was analyzed.4.After be in go riented, cut and polished,The polarization and non-polarization absorption spectra and fluorescence spectra of the crystal were measured at room temperature.According to the absorption spectra, the phenomenological intensity parameters Ω of Er3+ ions have been fited based on the Judd-Ofelt theory. Moreover.the spectral parameters of Er3+ ions including radiative transition probabilities Ajj, oscillator strengths Pjj , radiative lifetime τ and integrated emission cross- section Σ have been calculated. From the parameters mentioned above, the laser emission probability of Er:YbVO4 crystal was discussed.5. The Er:YbVO4 crystal has the fine spectrum performance nearl.5jim. Chose the fine quality crystal to carry on the laser performance..But there was no laser, it produce 的 the fluorescence, we give explanation according to the energy level of the Er3+ ion.
Keywords/Search Tags:Er:YbVO4 crystal, Judd—Ofelt theory, Raman scattering, Lattice Vibration, absorption spectra
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