Lee C-R, Fu T-L, Cheng K-T, Mo T-S, Fuh A Y-G
Department of Physics, National Cheng Kung University, Tainan, Taiwan 701, Republic of China.
Phys Rev E Stat Nonlin Soft Matter Phys. 2004 Mar;69(3 Pt 1):031704. doi: 10.1103/PhysRevE.69.031704. Epub 2004 Mar 22.
This study examines the surface-assisted photoalignment effect of dye-doped liquid-crystal films having a homogeneous alignment. Observations made using a polarizing optical microscope, a scanning electronic microscope, and an atomic force microscope confirm that the morphology of laser-induced surface-adsorbed dyes at the command surface strongly affects the orientation of liquid crystals (LC's) in a manner that depends significantly on the intensity and duration of the pumping. In weak-intensity regime, a homogeneous and fine layer of adsorbed dyes competes with a layer of ripple structure in reorienting LC's. These two effects dominantly cause LC's to reorient perpendicular and parallel to the polarization direction of the pump beam in the early and late stages, respectively. In the high-intensity regime, rough and inhomogeneous ribbonlike adsorbents produced by rapid and random aggregation and adsorption form on the top of the preformed microgrooves, reorienting LC's irregularly. This surface morphology does not enable photoalignment.
本研究考察了具有均匀取向的染料掺杂液晶薄膜的表面辅助光取向效应。使用偏振光学显微镜、扫描电子显微镜和原子力显微镜进行的观察证实，在指令表面激光诱导的表面吸附染料的形态以一种显著依赖于泵浦强度和持续时间的方式强烈影响液晶（LC）的取向。在弱强度 regime 下，均匀且精细的吸附染料层与波纹结构层在使 LC 重新取向方面相互竞争。这两种效应分别在早期和后期主要导致 LC 垂直和平行于泵浦光束的偏振方向重新取向。在高强度 regime 下，由快速且随机的聚集和吸附产生的粗糙且不均匀的带状吸附剂形成于预先形成的微沟槽顶部，使 LC 不规则地重新取向。这种表面形态无法实现光取向。
