Electrooptic And Piezo-resonance Enhancement Properties Of Potassium Lithium Tantalate Niobate Single Crystals

As a good nonlinear electrooptic and electrical controlled holographic material,potassium tantinate niobate KTa_1-xNb_xO₃（KTN） was investigated and appliedbroadly. Current research work about KTN family is focusing on Ta-richcomposition, which has low Curie temperature near room temperature. Ta-rich KTNcrystal has large Kerr coefficient however the heat created by materials will induceinstability when the material was used in device. But for Nb-rich KTN system,through modifying the Ta-Nb ratio, we can obtain high Curie temperature and goodlinear electrooptic property at room temperature. At the meantime, KTN seriesmaterials also show excellent piezoelectric properties, thus KTN series crystal isone kind of multifunctional material deserve to be studied. But owing to thedifficulty of ferroelectrics single crystal growth, the report about Nb-rich KTNseries single crystal is scare.With a slight Li doped, high quality K_0.95Li_0.05Ta_1-xNb_xO₃（x=0.52,0.60,0.69and0.78, KLTN） single crystals were grown using Top Seeded Melt Growth method.The optical, dielectric phase transition, thermal expansion and linear electroopticproperties of KLTN single crystals were investigated. As piezoelectric-electroopticmultifunctional material, the piezo-resonance enhanced the electrooptic effect ofNb-riched KLTN single crystal was reported at the first time.For room temperature ferroelectric KLTN single crystal, good opticaltransmittance can be obtained after cutting, polishing and poling processing. Theultraviolet absorbing edge and band gap of KLTN single crystals were determinedby transmittance spectrum. The refractive indices of four compositions of KLTNsingle crystals were measured accurately by using the minimum deviation method.The Sellmeier’s dispersion equations of refractive indices and the Sellmeier opticalcoefficients for KLTN single crystals were obtained in terms of least squares fit.The temperature and frequency dependent dielectric properties of KLTN singlecrystals were investigated. The compositions and frequency dependent Curietemperature of Nb-riched KLTN singe crystal were determined.The thermal expansion strain and coefficient of KLTN single crystal werestudied by using LVDT method. Accoding to the thermal expansion results, analysethe relationship between structure phase transition and temperature, compositions,orientation. Comparing the results of dielectric and thermal expansion, discuss thedata peak disagreement by using the composition inhomogeneity. Comparing theresults of paryelectric and thermal expansion, the sponteous and dynamic local polarization mechanism of KLTN single crystals were studied.The low frequency dependent linear electro-optic （EO） properties of KLTNseries single crystals were studied at room temperature. The EO coefficients γ₃3, γ₁3,γ₅₁and effective EO coefficients of KLTN single crystals at the wavelength of0.633nm were measured. The large value of γ₅₁for KLTN series single crystals wasreported at the first time. The orientation dependent corresponding electroopticcoefficient of KLTN single crystal was calculated and simulated based on axesrotation theory and experimental results. It is found that owing to the contribution ofγ₅₁, the maximum orientation of EO coefficient in3-dimension space is deviatingfrom the [001] direction. The piezo-resonance enhances the EO properties for KLTNseries single crystals under high frequency modulation field were studied at the firsttime. The results indicated that the EO response sharply increase near resonancepeak where the EO coefficient is comparable with that at low frequency. Accordingto these results, KLTN series multifunctional material may obtain more broadlyapplication space.The linear EO properties and other related properties of KLTN series singlecrystals were investigated in this work. It is found that KLTN series single crystalhas large potential to optical-piezoelectric-mechanism coupling high qualitymultifunctional materials.