利用准速度匹配技术可以实现大调制度的电光相位调制器，从而可以用来展宽激光频谱，它在光谱学、激光变频以及改善激光均匀性等方面有重要应用。当大功率激光通过调制器时，要求晶体的通光面积越大越好，所以大面积并且具有较大厚度的铁电晶体的室温极化技术成为准速度匹配实现的关键技术。详细研究了大面积并且厚度达到1 mm的钽酸锂晶体的电场室温极化过程，针对在极化过程中外部施加高电压时产生的回流现象，采用了改变极化时间来抑制，取得了较好的效果。利用热释电和化学腐蚀方法，成功地实现了钽酸锂晶体的大面积畴反转。该种技术同样可以用于其他大面积铁电晶体的极化。

Quasi-velocity-matching can be used to realize electron-optics phase modulator with high modulation index, which has essential applications in spectroscopy, laser frequency conversion and improving laser beam uniformity. When laser beam with high power propagates through the modulator, the larger aperture of the device is necessary, so the poling technology on ferroelectric crystal with large-area and high-thickness is essential for high power quasi-velocity-matching. In this paper, the electrical-poling process in room temperature on LiTaO3 crystal with the thickness of 1mm is studied in detail. In order to restrain back current during poling process, control of electrical poling time is adopted in the experiments. large-area domain inversion of LiTaO3 is successfully realized proved by thermoelectric effect and chemistry etching method. The proposed technology can be also employed in other ferroelectric crystal poling.