竞争非局域介质中空间孤子传输特性和光束调控研究

Nonlocal spatial solitons have potential applications in all-optical signal processing and optical interconnects due to their low power and particle-like nature on interactions. The spatial solitons in competing nonlocal media (SSCN) not only possess the merit of nonlocal solitons but also possess the special dynamic behavior. In addition, the competing effect of nonlocal nonlinearities affects the interaction of solitons, which leads to repulsion of in-phase bright solitons. This project aims to carry out SSCN experiment in Nematic Liquid Crystals and designs optical splitters based on Nematicon interactions. Firstly, we establish the competing nonlocal model in Nematic Liquid Crystals based on the reorientation and thermal effects which are induced by the input beams, and we investigate the character and dynamic of the soitons based on this modle. And then we produce the liquid crystal cell and carry out the SSCN experiment by adjusting the polarization of the incident light to control the competing nonlocal nonlinearities of nematic liquid crystal，at the same time, carry out the experiment which aims to investigate the beam steering technology with large angle in nematic liquid crystal. At last, we investigate the effect of transverse nonlocality and nonlinearity on the interaction between solitons and the propagation of the weak signal beam in the waveguide induced by the solitons interaction, and we develop the optical splitters based on the Nematicon interactions. This research not only enriches the nonlocal soliton phenomenon but also introduces a new way to control the beam in micro structure.

非局域空间孤子具有低功率、类似粒子的弹性碰撞特性，因此在光信息处理和光连接领域具有潜在应用。竞争非局域介质中的空间孤子（SSCN）不仅拥有非局域孤子的优点还具有独特的动力学行为。此外，竞争非局域效应改变了孤子间的相互作用，如导致同位相亮孤子间存在排斥力。本项目旨在利用向列相液晶首次开展SSCN实验、利用向列相液晶中孤子相互作用实现光控分光器件。首先，从向列相液晶的光致热效应和分子取向效应出发建立竞争非局域模型，通过模型的解研究孤子的特性及动力学行为；其次，制备液晶盒开展SSCN实验，调节入射光的偏振态控制液晶的热效应和分子取向效应来观察SSCN形成条件，探索向列子大角度精确控制技术。最后，研究横向非局域程度和非线性系数对孤子相互作用的影响，研究弱信号光在向列子相互作用诱导波导中的传输行为，开发基于向列子相互作用的光控分光器件。该研究拓展非局域孤子理论，为微结构中光束控制提供新方法。

本项目分为两个研究部分：首先数值计算了亮孤子及亮孤子对由非局域介质进入竞争非局域介质后的传输行为。发现，非局域亮孤子进入竞争非局域介质后以呼吸子的形式传输。非局域偶极孤子进入竞争非局域介质后分裂成两个独立传输的亮孤子。有趣的是，反位相非局域亮孤子组成的震荡束缚态进入竞争非局域介质后的传输行为与界面（非局域介质与竞争非局域介质的界面）位置有关。当界面选到节点（非局域孤子间距离取最小值的点）附近时，震荡束缚态分裂成两个独立的孤子；界面选到其它位置时，震荡束缚态以准束缚态形式传输。该发现为光的传输与控制提供新的方法。. 其次，提出简化模型描述光在向列相液晶中的传输。基于该模型分析了热效应对向列相液晶中光束传输的影响。发现热效应会削弱分子取向效应。因此，热效应会改变向列相液晶中空间孤子的特性。热效应会引起材料折射率各向异性横向方向的变化。热效应导致折射率各向异性的横向不均匀分布，光束诱导的折射率改变量会出现特殊的横向分布。此外，热效应对光束传输的影响不是孤立的还和分子取向效应的非局域程度有关。分子取向效应的非局域程度越大热效应对光束传输的影响越小。