Chunhui Yang

Growth of large PbWO4 single crystals by Czochralski method

Abstract Large size PbWO4 crystal was grown by Czochralski method. The dopant Fe3+ in the raw material and the annealing technology affected the transmittance at 420xa0nm. The transmittance at 420xa0nm obviously decreased when the Fe3+ content was higher than 10xa0ppm. The vacuum annealing improved the transmittance, whereas the oxygen-rich annealing decreased the transmittance. It was considered that the absorption at 420xa0nm resulted from Pb3+ in the crystal.

Enhancement of 1.54 μm emission in Er:LiNbO3 crystal by codoping with Zn2+ ions

Abstract The enhanced intensity and lengthened lifetime of 1.54 μm emission were observed for Er:LiNbO 3 crystal codoped with Zn 2+ ions. The ZnO codoping led to the reduction of the green upconversion emission in Er:LiNbO 3 crystals. The decay trace of the 4 S 3/2 → 4 I 15/2 was obviously nonexponential for Er:LiNbO 3 codoped with 0 and 3 mol.% ZnO, but became exponential for one codoped with 6 mol.% ZnO. The OH − absorption spectra showed after codoping with Zn 2+ ions, the OH − absorption peaking position shifted from ∼3495 to 3484 cm −1 , and the absorption cross section decreased. These spectroscopic characteristics suggested that the improvement of 1.54 μm emission was attributed to the reduction of Er 3+ cluster sites.

Effect of lead vaporization in growth process on the luminescence property of PbWO4 crystal

Abstract PbWO4 crystals were grown by Bridgman and Czochralski method, respectively. The ratio of Pb to W in the crystals was lower than stoichiometry because of the lead vaporization from the melt in growth process. The atomic ratio of Pb to W became lower gradually from head to tail of the crystal. This resulted in the decrease of transmittance and the decrease of intensity of emission peak. At the same time, the emission peak was shifted to the longer wavelength. Compared with Czochralski method, the vaporization of lead was well controlled in growth process of Bridgman.

IMPROVEMENT OF NONVOLATILE BLUE PHOTOREFRACTIVE PROPERTIES IN In:Ce:Cu:LiNbO3 CRYSTALS

The In:Ce:Cu:LiNbO3 crystals used in this work were grown by Czchralski method. The key parameters: the exponential gain coefficient Γ, the diffraction efficiency ηS, the response time τw, the dynamic range M/#, the sensitivity S and the maximal refractive index change Δnmax were measured with conventional two beam coupling. The optimal values of Γ, ηS, M/#, S and Δnmax achieved are 44.7, 68.6%, 6.02, 0.471 cm/J and 5.37 × 10-5, respectively. It was found that the blue light photorefractive properties of Γ, ηS, M/#, S and Δnmax increased with increasing In3+ ions concentration, while the red light photorefractive properties of Γ, ηS, Δnmax decreased with increasing In3+ ions concentration. The nonvolatile holographic storage properties were measured by both the dual wavelength and two color techniques. The maximal diffraction efficiency and fixing diffraction efficiency using the dual wavelength technique were doubled compared to those obtained in using the two color technique. The sensitivity and nonvolatile sensitivity were one order of magnitude higher than those by the two color technique. The photorefractive property enhancement by the dual wavelength technique was investigated.