液晶光学相控阵光束偏转效率研究(英文)

Theoretical Study on Beam Steering Efficiency of Liquid Crystal Optical Phased Array

液晶光学相控阵(LCOPA)的光束偏转效率(OSE)定义为一级衍射光强与总入射光强的比值,它受很多因素的影响,因此建立一个数值分析的模型来分析光束偏转效率。这个模型将液晶光学相控阵器件当作一个相位光栅和一个振幅光栅的组合体,可控变量既包括几何结构参数又包括相位分布的参数。理论研究了光束偏转效率和三类因素即偏转角、器件参数及理想与实际相位分布误差之间的关系,提出了改善光束偏转光效率的方法。结果表明随着偏转角的增大光束偏转效率将会减小,而增大填充因子、减小像素大小会提高光束偏转效率。均匀排布像素并不能获得最佳偏转效率,需要使用如时域有限差分等方法来得到最佳的像素分布。减小相邻相移器之间的间隔、提高相位回置值可以明显提高光束偏转效率。

The overall steering efficiency（OSE） of the liquid crystal optical phased array（LCOPA） is defined as the ratio of the first order diffraction＇s intensity and the incident intensity.It is affected by many factors.A numerical analysis model is established to analyze the OSE.The model regards a LCOPA as the combination of a phase grating and an amplitude grating,and thus,model parameters include not only the geometric structural parameters but also the parameters of the phase profile.The general relations between the OSE and three kinds of factors,i.e.steering angles,the parameters of the LCOPA and errors between ideal and practical phase profiles,are studied.Ways to improve the OSE are proposed as well.Results show that increase of steering angles reduces the OSE while raising fill factors and reducing the pixel size can improve the OSE.Proportional spacing pixels are not the optimal distribution for improving the OSE,for which the method of finite-difference time-domain（FDTD） should be used to design the optimal pixel distribution.Reducing the space of two adjacent phase shifters and raising the phase reset value can improve the OSE obviously.