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Effect of Different Valency Optical Damage Resistant Ions on Defect and Optical Properties of Er:LiNbO3Crystals

Author: QianYanZuo
Tutor: WangRui
School: Harbin Institute of Technology
Course: Chemical Engineering and Technology
Keywords: Er-doped LiNbO3 First principle theory Optical damage resistant ion defect structure 1.54μm emission
CLC: O77
Type: PhD thesis
Year: 2012
Downloads: 55
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Abstract


Er-doped wavelength amplifiers （EDWAs） will be one of the key componentsof futher microphotonic systems, and Er:LiNbO3crystals, used as the host materialsfor EDWAs, have excellent advantages such as the high stabilization and integration.Furthermore, Er:LiNbO3crystals could combine the laser performances of Er3+ionwith the nonlinear characteristics presented by LiNbO3crystal. Er:LiNbO3emits1.54μm near infrared emission, which corresponds to the standard communication“window” wavelength. Howerve, the practical applications of Er:LiNbO3crystalsare limited by the optical damage effect. Different valence Zn2+, In3+and Zr4+ionsare chosen to enhance the optical damage of LiNbO3crystals. We performinvestigations on the effect of different valence optical damage resistant ions on thedefect structure and optical characteristics of Er:LiNbO3crystals, which provide thetheoretical and experimental direction for us to obtain the high efficient1.54μmnear infrared emission.The geometry structure of LiNbO3crystals doped with Zn2+, In3+and Zr4+ionsare calculated by the first principle theory, which shows that Zn2+, In3+and Zr4+ionsoccupy Li sites firstly. The stuies on the stability of Zn2+, In3+and Zr4+ionsoccupied Li sites show that Zn2+ions will push Er3+ions into Nb sites, and the Er3+clusters sites are formed in Er:LiNbO3crystals, and In3+ions have little effect on theoccupancy of Er3+ions, and the low stability of Zr4+ion makes Er3+ions stilloccupy Li sites.The Er:LiNbO3crystals are grown by Czochraski method. The defect structureof Er:LiNbO3with different Er3+ion concentration, as well as the near infraredemission, upconversion emission and mechanism under different excitationwavelength are studied. It has been proposed that the formation of Er3+cluster sitescould increase the rate of cross relaxation processes. Under980nm excitation, Er3+cluster sites will suppress the1.54μm near infrared emission. Studies on the effectof [Li]/[Nb] ratio （is equal to0.94,1and1.25, respectively） on the defect structureand optical characteristics of Er:LiNbO3crystals show that as for [Li]/[Nb]=1, theEr3+cluster sites are dissociated and the strongest1.54μm emission is observed inEr:LiNbO3crystal.The studies on the defect structure and optical characteristics of Er3+（3mol%）:LiNbO3crystals doped with3,6and7mol%Zn2+ions show that thethreshold concentration of Zn2+ion is not affected by Er3+ions in Zn/Er:LiNbO3crystal. When the concentration of Zn2+ions is lower than its threshold, the Er3+cluster sites are dissociated by Zn2+ions, which results in the enhancement of1.54 μm near infrared emission. When the concentration of Zn2+ions is higher than itsthreshold, the reformantion of Er3+cluster sites are observed, which decreases the1.54μm near infrared emission. Combined the first principle theory with the relationbetween the occupancy and optical characteristics of Er3+ions, the Zn/Er:LiNbO3crystals with the3/1.5,6/1and7/1.5mol ratio of Zn2+/Er3+are grown. The strongest1.54μm emission is found in Zn/Er （6mol%/1mol%）:LiNbO3crystal. Stuies on theOH-absorption Lorentz three decomposition and the decay curves of upconversiongreen emission show that Zn2+ions would push Er3+ions from Li sites into Nb sites,and the Er3+cluster sites are formed at lower concentration.The defect structure and optical characteristics of Yb/Er:LiNbO3crystal dopedwith1,2and3mol%In3+ions are studied. The experiemtal results show that Yb3+and Er3+ions decrease the threshold concentration of In3+ions. When theconcentration of In3+ion is equal to its threshold, the Er3+cluster sites are formed.The formation of Er3+cluster sites is favor for the1.54μm near infrared emissiondue to the sensization effect of Yb3+ion. The strongest intensity of1.54μmemission is observed in Yb/Er:LiNbO3crystal codoped with the thresholdconcentration of In3+ions.Zr4+ion doping enhances the1.54μm emission in Zr/Er:LiNbO3andZr/Yb/Er:LiNbO3crystals. Raman spectra and the decay curves of Er3+4I11/2→4I15/2transition at1020nm indicate that the enhancement of the1.54μm emission arisesfrom the increased maximum phonon energy of host material. The near infraredspectra of Yb/Er:LiNbO3crystals doped with the different valence Zn2+, In3+andZr4+ions suggest that Zn2+doping decreases the1.54μm emission, In3+ions havealmost no effect, and Zr4+ions lead to a drastical increase of1.54μm emission.Zr/Yb/Er:LiNbO3crystal could be considered as the most outstanding host materialsfor waveguides.The spectral characteristics of Er:LiNbO3and Yb/Er:LiNbO3crystals dopedwith Zn2+, In3+and Zr4+ions are studied by Judd-Ofelt theory, and Zr/Yb/Er:LiNbO3crystal has the largest spectroscopic quality factor. The emission performance of1.54μm emission is analyzed by McCumber and Füchtbauer-Ladenburg theory. Allthe crystals have large emission cross section, which is suitable for the hostmaterials of EDWA.

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