Stucture And Properties Of Holmium Doped Lithium Niobate Crystals With Varied Holmium Concentration

Ho: LiNbO3 single crystals with no macroscopic defects but high optical quality were grown by the Czochralski method. The optimum process conditions for growing Ho: LiNbO3 single crystals were determined.IR absorption spectra and UV-Vis absorption spectra were tested, and they were investigated to find the effect of Ho³⁺ doping concentration on the position of OH- absorption peak, So that the occupying mechanism of the dopants was found. XRD of (300) of crystals were tested. The effect of Ho³⁺ doping concentration on the FWHM of XRD pattern was investigated, and a rule was found: the high the concentration of Ho³⁺, the worse the quality of the crystals are.Emission spectra were test with the 250 nm exciting light. Up-conversion emission spectra were test with the 620 nm exciting light. The effect of Ho³⁺ doping concentration to the position and intensity of emission light was investigated. Mechanism of up-conversion were ESA(excited state absorption) . The corresponding spectral terms of absorption peak were explained according to the energy level scheme of Ho³⁺. Phenomenological intensity parameters, spontaneous activity emission transition probability, life time of energy level, fluorescence branching ratio were calculated according to Judd-Ofelt theory. Transitions which are aped to find emission of laser were pointed out. The effect of Ho³⁺ doping concentration to the spectral parameters was investigated. Spontaneous activity emission transition probability and life time of energy level were found to change in the opposite direction as the change of Ho³⁺ doping concentration.Optical damage resistance of crystals was studied using transmission photospheric facula deformation method. The effect of Ho³⁺ doping concentration to the optical damage resistance was investigated, and it was found that the higher the concentration of Ho³⁺ doping is, the stronger the optical damage resistance is. But the effect of Ho³⁺ doping concentration to the optical damage resistance was found changes little as the Ho³⁺ doping concentration is higher than 1mol%.