SGER: Optical Parametric Processes in Ferroelectric Liquid Crystal Filled Capillary Tube Waveguides

一种新的二阶非线性光学（NLO）材料被开发出来：X(2)铁电液晶（FLCs）。传统的FLCs易于在宽厚度范围内形成低光损耗的极性薄膜，并已被证明是光波导。新的X(2) FLCs结合了传统FLCs的可加工性和有用量级的热稳定NLO敏感性。此外，光学性质，如双折射，介电常数和NLO性质是高度定制的化学合成和混合。在这项探索性研究的小额资助中，将研究使用cm长，um内径充满X(2) FLCs的毛细管进行光学参数过程的诱人可能性。在这项工作中将回答的关键问题包括：1)毛细管中的内在导向结构是什么——偏振矢量场是极性的吗？如何控制？2) flc芯光波导有哪些可能的相位匹配方案？实验研究了FLC在毛细管中的对准，并对FLC材料参数如液晶相序、螺旋距、倾角、并确定了毛细管制备对对准特性的影响。利用董事对齐信息，通过求解与位置相关的相对介电常数和非线性极化率的波动方程，可以精确地模拟二次谐波的产生过程。最后，利用X(2) FLC混合物Displaytech MX-5679在um内径，cm长的毛细管中进行近红外辐射的倍频实验研究。

A new class of second order nonlinear optical (NLO) materials has been developed: X(2) ferro- electric liquid crystals (FLCs). Conventional FLCs readily form low- light-loss polar films in a wide range of thicknesses, and have been demonstrated as optical waveguides. The new X(2) FLCs combine the processibility of conventional FLCs with thermodynamically stable NLO susceptibility of useful magnitude. In addition, optical properties such as birefringence, dielectric permittivity, and NLO properties are highly customizable by chemical synthesis and mixing. In this Small Grant for Exploratory Research, the attractive possibility of using centimeter long, um inner diameter capillary tubes filled with X(2) FLCs for optical parametric processes will be investigated. Key questions which will be answered in this work include the following: 1) What is the intrinsic director structure in the capillary tubes--is the polarization vector field polar, and how can it be controlled? 2) What are possible phase matching schemes for FLC-cored optical waveguides? FLC alignment in capillary tubes will be examined experimentally, and the effect of FLC material parameters such as liquid crystal phase sequence, helix pitch, tilt angle, and capillary tube preparation on alignment characteristics will be determined. Using director alignment information, second harmonic generation processes will be accurately modeled by solving the wave equation with position dependent relative permittivity and nonlinear polarizability. Finally, frequency doubling of near-infrared radiation using the X(2) FLC mixture Displaytech MX-5679 in um inner diameter, centimeter long capillary tubes will be investigated experimentally.