College of Optics and Photonics, University of Central Florida, Orlando, Florida 32816, USA.
School of Electronic Science and Engineering, Southeast University, Nanjing 210018, China.
Sci Rep. 2017 Jan 5;7:39923. doi: 10.1038/srep39923.
We demonstrate a simple yet high performance phase grating with switchable diffraction angles using a fringe field switching (FFS) liquid crystal (LC) cell. The LC rubbing angle is parallel to the FFS electrodes (i.e. α = 0°), leading to symmetric LC director distribution in a voltage-on state. Such a grating exhibits three unique features: 1) Two grating periods can be formed by controlling the applied voltage, resulting in switchable diffraction angles. In our design, the 1 diffraction order occurs at 4.3°, while the 2 order appears at 8.6°. 2) The required voltage to achieve peak diffraction efficiency (η32%) for the 1 order is only 4.4 V at λ = 633 nm as compared to 70 V for a conventional FFS-based phase grating in which α ≈ 7°, while the 2 order (η27%) is 15 V. 3). The measured rise and decay time for the 1 order is 7.62 ms and 6.75 ms, and for the 2 order is 0.75 ms and 3.87 ms, respectively. To understand the physical mechanisms, we also perform device simulations. Good agreement between experiment and simulation is obtained.
我们使用边缘场开关（FFS）液晶（LC）单元展示了一种具有可切换衍射角的简单但高性能的相位光栅。LC 的摩擦角与 FFS 电极平行（即 α=0°），从而在电压开启状态下产生对称的 LC 指向矢分布。这种光栅具有三个独特的特点：1）通过控制施加的电压可以形成两个光栅周期，从而实现可切换的衍射角。在我们的设计中，1 级衍射发生在 4.3°，而 2 级衍射发生在 8.6°。2）与传统的 α ≈ 7°的 FFS 基相位光栅相比，在 λ = 633nm 时，实现 1 级最大衍射效率（η32%）所需的电压仅为 4.4V，而 2 级（η27%）所需的电压为 15V。3）1 级的上升和下降时间分别为 7.62ms 和 6.75ms，2 级的上升和下降时间分别为 0.75ms 和 3.87ms。为了理解物理机制，我们还进行了器件模拟。实验和模拟结果吻合良好。
