基于亚波长光栅结构的硅基液晶器件模型研究

金(Au)亚波长光栅被溅射到经典硅基液晶(LCoS)的ITO电极上,它与薄液晶盒和底层铝电极组成复合共振波导结构,简称GLCoS。与基于液晶传播效应的LCoS截然不同,在GLCoS中,上电极的表面等离激元与光栅槽中的TM-FP (TM-Fabry Pérot)共振耦合,诱导一个0阶反射的相位调制;铝(Al)电极既是反射背板又与Au光栅、薄液晶盒组成波导,使共振耦合得到增强。在操控光波阵面的同时,GLCoS也作为电控器件,施加电压改变液晶的折射率,进而控制开腔FP的边缘介质条件,达到有源0~2π相位调制。实验结果表明,本文结构可用于1μm量级像素的相位空间光调制器,在高空间带宽积的全息视频显示中具有广阔的应用前景。

Model of Liquid Crystal on Silicon Device with Sub-Wavelength Grating Structure

Herein, a sub-wavelength gold(Au) grating is sputtered onto an indium tin oxide electrode of a classical liquid crystal on silicon(LCoS). After it is mounted on a thin liquid-crystal cell with a bottom aluminum electrode, a composite resonant waveguide structure, namely GLCoS, is created. In contrast to LCoS that operates based on liquid-crystal propagation effects, in the GLCoS, the surface plasmon of the upper electrode is resonantly coupled with a TM-Fabry-Pérot(TM-FP) resonator in the grating slits to induce a phase modulation of zero-order reflection. The aluminum electrode acts as a reflective backing plate and contributes the waveguide with the Au grating and thin liquid-crystal cell, which enhances the resonance coupling. While acting as an optical device to control the wavefront, the GLCoS also operates as an electronic control device, applying voltage to change the refractive index of the liquid crystal cell;it can control the dielectric condition of the open cavity FP at the boundary to achieve an active 0--2π phase modulation. The experimental results show that the proposed GLCoS structure can be used in phase-spatial light modulators with the 1-μm-level pixel, and it has prospects for application in holographic video displays with high spatial bandwidth product.