液晶光学相控阵的激光诱导非线性效应机理研究

Based on the physical model of non-mechanical liquid crystal optical phased array, a bunch of fundamental problems of this new mechanism particularly on the laser induced nonlinear effect would be further analyzed in this proposal. In spite of directly experimental measurements, in this proposal, the physics of laser induced nonlinear effect on liquid crystal optical phased array is studied to evaluate the propagation properties of coherent far field and pulse expansion. Meanwhile, laser induced reorientation of liquid crystal molecules and Freedericksz transition are solved on the approach of building a theoretical thermodynamic model on the device, the structure of which is solid-liquid mixed, and the working medium of which is anisotropic liquid crystal. Even more, in this model, there are two kinds of heat sources should be considered together: a 2-D surface heat source of liquid crystal film with a thickness of 10 micros and 3-D volume heat source of base glass with a thickness of 1 millimeter. The models of Newtonian fluid and elastomer are suggested into the overall theoretical analysis. Then, parameters of filled liquid crystal and geometric design would be optimized by some new technologies basing on the theoretical results including the numerical relationship between nonlinear coefficient and parameters of input laser and liquid crystal device. Finally, a couple of confirmatory experiments are designed and set up using our previous self-developed liquid crystal optical phased array as the core module to verify the above theoretical models including steady models and dynamic models. Validity and applicability of these models would also be proposed according to the obtained experimental results to promote the development of this non-mechanical technique of liquid crystal optical phase array.

本项目以非机械式液晶光学相控阵作为物理模型的核心，研究其在应用系统中出现激光诱导非线性效应的基础理论问题。当前针对激光诱导非线性效应的研究以实验观测表象为主，而本项目将探寻激光诱导非线性效应的产生机理，在此基础上研究其对远场光束特性参数的影响。研究内容包括：构建液晶光学相控阵激光诱导非线性效应物理模型，通过对液晶各向异性、固液混合结构的热力学分析，并综合考虑液晶薄膜二维面热源、基底玻璃三维体热源、液晶牛顿流体和基底弹性体的独立特性，研究激光诱导下液晶分子取向重组和Freedericksz转变；针对连续和脉冲两种激光工作模式，研究激光参数、器件参数与诱导非线性效应的数值关系，并进行材料和工艺参数优化方法研究；最后，基于自行研制的液晶相控阵器件，搭建原理验证实验平台，进行相关模型的验证实验，分析实验结果，验证理论模型的正确性和适用性，从而推动基于液晶光学相控阵的非机械光束扫描技术的发展。

针对空间信息网络中多用户组网和信息高速传输的需求，探索基于液晶光学相控阵天线的激光通信机理和多址接入组网体制、多参量动态波束控制原理，解决多用户动态连接、快速捕获、高精度跟踪方法。申请人在本重大研发计划培育项目的支持下，已经完成相关的理论模型研究，并搭建原理验证实验平台，开展模拟验证实验，完成一系列创新方法的验证。包括：高阶光栅法实现液晶光学相控阵宽覆盖范围、幅相共调法实现液晶光学相控阵多波束生成、斜入射光束的后向传输特性、消偏振二维波束扫描系统、逻辑子孔径相干波束控制方法、随机波束扫描方法提高捕获概率、多用户相控捕跟接入方法等。发表学术论文 26 篇，其中， SCI 收录源刊论文7 篇，EI期刊3篇，学术会议研究论文 11篇，5篇发表在国际顶级光学会议 SPIE Photonics West 中，并做会议特邀报告6次；授权或申请发明专利9 项；已经完成学位论文5本，为液晶光学相控阵器件、模块、系统的未来综合应用提供理论支撑。