基于铁电畴壁局域非线性的激光脉冲时频测量技术研究

The conventional pulse diagostic measurements, such as auto- and cross-correlation techniques, cannot be used through the whole bandwidth of the material and are difficult to achieve high dynamic ratio and spatial resolution. Here, we propose a novel pulse characterization method based on a new special material- - the ferroelctric domain wall, by using which the spatially dispersed Cherenkov harmonics are generated and the spectral and intensity information is transferered and recorded, and then the original parameters of the pulse is reconstructed by proper algorithms. This pulse characterization method does not only provide single-shot measurements, but also enhances the dynamic ratio during measurements and can be used through the whole bandwidth of the material due to the enhanced nonlinearities in ferroelectric domain wall and the Cherenkov phase matching condition.

传统超短脉冲测量采用的自相关、互相关技术难以提供全频范围可用、高动态对比度、高空间分辨率的测量手段。本方案提出一种基于新材料新原理的型脉冲时频特性单次精确测量技术。利用铁电晶体畴壁产生的具有空间色散特性的切伦科夫和频信号传递频谱及强度信息，同时建立相适应的反推算法获得精确完整的脉冲时频参数。这种技术不仅可以实现单次脉冲测量，同时因畴壁增强的局域非线性性质及切伦科夫型位相匹配的特性，可以提升测量的动态对比度、获得高空间分辨率并在材料透明窗口的全频范围内可用。

提出一种新的利用铁电晶体畴壁增强非线性性质实现超短脉冲单发FROG测量的技术，并通过实验验证了该技术的可行性。研究中依此实现了基于铁电晶体畴壁非线性切伦科夫辐射的自相关测量和单发FROG测量，还发现诸如晶体界面这样的不同于畴壁的非线性界面可以产生光束质量更好的非线性切伦科夫辐射，能够进一步提高脉冲测量的精度。此外，还研究了晶体非线性界面上其他新型谐波产生过程，进一步掌握了铁电晶体非线性界面在谐波产生过程中的特性。