Fringing fields in a liquid crystal spatial light modulator for beam steering
Fringing fields in a liquid crystal spatial light modulator for beam steering
复制标题
DOI：
10.1080/09500340408230419
复制
发表时间：
2004-05
影响因子：
1.3
通讯作者：
E. Haellstig;J. Stigwall;T. Martin;L. Sjöqvist;M. Lindgren
中科院分区：
文献类型：
--
作者：
E. Haellstig;J. Stigwall;T. Martin;L. Sjöqvist;M. Lindgren
摘要相位调制空间光调制器（SLM）可以用来改变激光波前的形状，从而实现激光束的偏转或形状的改变。本文报道了一维液晶空间光调制器的表征、模拟和优化结果。该器件在LC层厚度和像素间距之间具有大的比率，这导致像素之间的边缘场。实际上，所应用的相位图案将被低通滤波，并且高频分量的损失限制了例如可用的转向范围。提出了一种方法，其中在远场的强度测量被用来确定如何在SLM的相位调制失真。通过对电极像素结构内的液晶指向矢分布进行建模来确定该器件的非均匀光学各向异性。采用时域有限差分法（FDTD）模拟计算了光在LC中的传播。将模拟的相位畸变与实验结果进行了比较。利用测量和模拟结果，提出了一种提高衍射效率的电压补偿方案。它表明，修改的电压模式可以得到一个更好的实现的高频分量的相位分布和最大转向角的增加的一个因素2。
Abstract Phase modulating spatial light modulators (SLMs) can be used to alter the shape of a laser wavefront to achieve a deflection or change in the shape of a laser beam. This paper reports the results of characterization, simulation and optimization of a one-dimensional liquid crystal (LC) SLM. The device has a large ratio between LC layer thickness and pixel pitch that results in a fringing field between pixels. In effect, the applied phase patterns will be lowpass filtered and the loss of high frequency components limits, for instance, the usable steering range. A method is presented where intensity measurements in the far field are used to determine how the phase modulation at the SLM is distorted. The inhomogeneous optical anisotropy of the device was determined by modelling the liquid crystal director distribution within the electrode-pixel structure. Finite-difference time-domain (FDTD) simulations were used to calculate the light propagation through the LC. The simulated phase distortion was compared with the experimental results. A voltage compensation scheme to improve the diffraction efficiency was developed utilizing the measured and simulated results. It is demonstrated that a modification of the voltage patterns can give a better realization of high frequency components in the phase distribution and an increase in maximum steering angle by a factor two.