The Study Of Electro-optic Responseand Mechanism In Potassium Tantalat Niobate Near The Phase Boundary

With the rapid development of optical communication technology, the electro-optic crystal materials, which can realize high-speed optical modulation, has attracted more and more attention and has been widely studied. The potassium tantalant niobate(KTa1-xNbxO3,KTN) crystal, regarded as a new type lead-free electro-optic crystal, possess excellent electro-optic performance near the ferroelectric-paraelectric phase boundary. It is considered as the best material in the areas of electro-optic modulation, electro-optic holographic storage, and so on. This paper mainly studies the electro-optic dynamic response performance of KTN. Combined with the observation of polar nano-region(PNR), the origin of the temperature and the frequency characteristics were both analyzed near the phase boundary in KTN. This will help explore the relationship between the structure of the mesoscopic system and the the performance, in order to lay the theoretical and experimental foundation of practical application of KTN.Firstly, the high quality KTN crystal was grown by the top seeded solution growth method and the basic physical properties have been studied. The dielectric property was measured through the dielectric measurement system, to obtain the Curie temperatures, components and chemical formulas, based on the dielectric abnormal phenomenon. Considering the existence of PNR near the phase boundary in KTN, the reason of the dielectric property deviating from the Curie-Weiss law was analyzed. The grating spectrometer was used to represent the transmission and absorption spectra of KTN, ranged from 400 nm to 950 nm, and the forbidden band width was acquired.Then, the dynamic electro-optic response characteristics were studied systematically in KTN crystal. According to the theory of the refractive index ellipsoid, the quadratic electro-optic effect was deduced and described. The effective electro-optic coefficient was characterized by the Senamont single-beam compensation method, reaching 5.9×10-15 m2/V2. Considering the PNR near the phase boundary, the electro-optic response on the temperature and the frequency of electric field was analyzed. More than that, the superposition of the linear and the quadratic electro-optic effect leaded to a high-low peak-to-peak distortion phenomenon in the output waveform, which was induced by PNR. In order to account for the contribution of PNR further, a phase-only theory model was established and the distortion phenomenon was explained clearly.Finally, the electrostrictive effect and dynamic changes of PNR were studied. Using the Michelson interfering method system, the frequency denpendence of electrostrictive effect was measured in KTN, which can be comparied with the electro-optic properties. The influence of electrostrictive effect was deduced in the electro-optic coefficient measurement process, and the real electro-optic coefficient was given. Proceed from the internal polarization mechanism in KTN, it is explained that the frequency characteristics of the electro-optic and electrostrictive effect derived from the orientational polarization of inherent electric moment, namely PNR. The KTN was observed to obtain the response of PNR on temperature and electric field frequency by polarizing microscope near the phase boundary, which can fully prove the anlysis of the dynamic response of electro-optic and electrostrictive effect.