弛豫铁电单晶PMN-PT优异电光系数全矩阵测试及其机理研究

This project will study the optical and linear electro-optic properties of the relaxor ferroelectric single crystals Pb(Mg1/3Nb2/3)O3-PbTiO3(PMN-PT) and In-doped PMN-PT, which are very important functional materials and cause widespread concern in the international piezoelectric and ferroelectric academic fields. Firstly, we will determine the basic spectroscopic properties including the optical absorption edge position, forbidden band width, and the electronic transition by absorption spectrum. Secondly, the refractive indices and full matrix linear electro-optic coefficients of the single crystals will be measured in the case of different temperatures and different wavelengths. The effective electro-optic coefficient of the crystal and the half-wave voltage will be discussed, which are important electro-optic parameters. Then, full matrix piezoelectric constants will be measured, and the combined piezoelectric and electro-optic effects will be studied based on the complete set of electro-optic and piezoelectric constants. We will also study the influence of the inverse piezoelectric effect on the electro-optic modulation of ferroelectric crystals and find the way of how to enhance the electro-optic modulation performance by means of huge inverse piezoelectric effect. We will carry out a reasonable theory for optimal design, and find the best electro-optic modulator application state. Finally, the relationship between the excellent eleltro-optic properties and the huge piezoelectric properties will be studied to get the mechanism of the good electro-optic performance in these relaxor ferroelectric single crystals.

本项目将对近年来在国际压电、铁电学术领域引起广泛关注的热点材料体系，弛豫铁电单晶Pb(Mg1/3Nb2/3)O3-PbTiO3(PMN-PT)和In掺杂PMN-PT，的一般光学和线性电光性质进行实验测量与机理研究。首先，通过测量其吸收光谱，确定其光学吸收边位置、禁带宽度和电子跃迁等基本的光谱性质；其次，测量其在不同温度与不同波长情况下，单晶的折射率和电光系数全矩阵参量，讨论晶体的有效电光系数和半波电压等重要电光参数；然后，测量单晶的压电系数全矩阵参量，并在测量得到整套电光和压电参数的基础上，研究单晶的压电-电光联合效应，分析逆压电效应对铁电晶体电光调制性能的影响，以及如何充分利用铁电晶体巨大的逆压电应变去增强晶体的电光调制能力，并进行合理的理论优化设计，找到晶体最佳的电光调制状态；最后，研究此类单晶优异电光性能的机理及其与晶体巨大压电性能之间的关系。

随着光电信息技术的发展，电光调制器件迫切需要开发出具有更高开关速率、更大电光系数和更低半波电压的高性能电光材料。本项目对新型的弛豫铁电单晶Pb(Mg1/3Nb2/3)O3-PbTiO3(PMN-PT)和In掺杂PMN-PT，的一般光学和线性电光性质进行了系统的实验与理论研究。获得了PMN-PT、PIN-PMN-PT和KNNT等单晶的基本光学参数，如折射率，光学吸收边位置，禁带宽度等；得到了晶体的线性电光系数和压电系数；确定了晶体的折射率色散方程；研究了温度对晶体光学性质的影响规律；确定此类单晶最佳的电光调制状态；发现单晶的最佳电光调制性能并不发生在晶体的主轴坐标系下，利用坐标变换方法，考虑电光-压电耦合效应，确定了PMN-PT晶体的最佳电光调制方向。在最佳状态下，晶体的半波电压最大可降低10倍。本项目还揭示了此类单晶优异电光性能的形成机理是弛豫铁电单晶内部的微畴的高电学活性，为从本质上进行其电光性能的改性工作提供理论依据。