大偏转角液晶光栅波前测试系统研究

发布时间：2018-06-21 22:36

本文选题：大偏转角 + 液晶光栅　；参考：《长江大学》2016年硕士论文

【摘要】：光学相控阵技术的工作原理是在电光材料的电光效应下,通过改变加载在不同相控单元的电压来改变通过不同相控单元光波的相位、光强等光学特性,以此来达到对每个单元光波的独立控制。它在实现激光束偏转中应用很广泛。本文讲述的液晶光栅相控阵就是以液晶分子充当电光材料的光学相控阵。液晶分子在电场作用下,排列方向得到改变,且它们的折射率不同,使得通过它的光束方向发生一定角度的偏转。为了更够更好的实现液晶光栅角度的偏转,就要了解它的波前畸变情况。本文概括描述了液晶光栅相控阵和波前测量技术的发展情况,以及液晶光栅的性质和工作原理。分析了不同类型相位轮廓误差对液晶光栅器件性能的影响,以及液晶光栅的衍射光场特性,并用matlab仿真技术模拟了在不同情况下衍射光场光强、相位的分布情况,为液晶光栅波前测试方法的选择提供科学依据。通过分析选择出合适的波前测试方法即单一衍射级反演法来测量液晶光栅的误差相位轮廓,测量系统测出近场+1级衍射波前,用单一衍射级反演法来反演出此时液晶光栅的波前相位情况,把这个情况反馈给波控器。波控器就是对液晶光栅施加电压指令的装置,在它得到相位反馈后,根据测得的已知的电压-相位关系来改变施加电压数据,从而再度调整出射光束质量。这样不断反馈重复就可以得到高质量的偏转光束。研究了液晶光栅波前测量系统的光路结构。采用四边形径向剪切干涉法来测量衍射波前,该方法有剪切干涉法的优点,就是不需要引入参考波。通过液晶光栅发生衍射的光束在分束棱镜后被分成了两束光：反射光和透射光,分别对其扩束和缩束,最后在分束棱镜后面会合,一大一小两个光斑重合产生干涉条纹图。通过条纹图即可重构出衍射波前。通过光学设计软件来模拟这个光路结构,为能精确测量衍射波面,各元件间距符合4f系统的要求。建立一个开普勒望远系统结构用于缩、扩光束,模拟它的光路,并分析透镜参数对望远系统像差的影响以及分束棱镜偏转时的光路发生的变化。对不同载波频率的干涉条纹频谱和几种特殊波面入射时的干涉情况进行了仿真。仿真结果对测量系统的搭建及调试具有指导意义。搭建了液晶光栅波前测量系统,并对实际的大偏转角液晶光栅进行了实测实验。首先对该剪切干涉仪进行标定,并测试了液晶光栅的静态相位分布及光束偏转时的液晶光栅相位轮廓,最后对实验结果进行了分析。
[Abstract]:The principle of optical phased array technology is to change the phase and intensity of light waves through different phase control units by changing the voltage loaded in different phase control units under the electro-optic effect of electro-optic materials. In order to achieve independent control of each unit of light waves. It is widely used in the realization of laser beam deflection. The liquid crystal grating phased array described in this paper is an optical phased array using liquid crystal molecules as electro-optic materials. Under the action of electric field, the alignment direction of liquid crystal molecules is changed, and their refractive index is different, which makes the beam direction of liquid crystal deflect at a certain angle. In order to better realize the angle deflection of liquid crystal grating, it is necessary to understand its wavefront distortion. This paper describes the development of liquid crystal grating phased array and wavefront measurement technology, as well as the properties and working principle of liquid crystal grating. The effect of different phase profile errors on the performance of liquid crystal grating devices and the diffraction light field characteristics of liquid crystal grating are analyzed. The intensity and phase distribution of the diffraction light field are simulated by matlab simulation technology. It provides a scientific basis for the selection of liquid crystal grating wavefront measurement method. By analyzing and selecting the suitable wave front measurement method, that is, single diffraction order inversion method, the error phase profile of liquid crystal grating is measured, and the near field 1 order diffraction wave front is measured by the measuring system. The inversion method of single diffraction order is used to invert the wavefront phase of the liquid crystal grating at this time, and the situation is fed back to the wave controller. A wave controller is a device that applies voltage instructions to liquid crystal gratings. After phase feedback is obtained, the applied voltage data are changed according to the known voltage-phase relationship, and the beam quality is adjusted again. In this way, a high quality deflection beam can be obtained by repeated feedback. The optical structure of liquid crystal grating wavefront measurement system is studied. The quadrilateral radial shearing interferometry is used to measure diffraction wavefront. This method has the advantage of shearing interferometry, that is, there is no need to introduce reference wave. The beam diffracted by the liquid crystal grating is divided into two beams after beamsplitting prism: reflected light and transmitted light, which are expanded and shrunk respectively. Finally, they meet behind the splitter prism, and the interference fringes are produced by the coincidence of two light spots, one large and one small. Diffraction wavefront can be reconstructed by fringe pattern. The optical design software is used to simulate the optical structure. In order to accurately measure the diffraction wave surface, the distance between the elements meets the requirements of the 4f system. A Kepler telescope system structure is established to reduce and spread the beam, to simulate its optical path, and to analyze the influence of lens parameters on the aberration of the telescope system and the changes of the beam path when the beam splitting prism is deflected. The interference patterns of different carrier frequencies and several special wave planes are simulated. The simulation results are of guiding significance to the construction and debugging of the measurement system. The liquid crystal grating wavefront measurement system is built, and the real liquid crystal grating with large deflection angle is tested. First, the shear interferometer is calibrated, the static phase distribution of liquid crystal grating and the phase profile of liquid crystal grating during beam deflection are measured. Finally, the experimental results are analyzed.
【学位授予单位】：长江大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：O753.2

【相似文献】