The Two-dimension Diffraction and the Milky Haze of a Large-scale Topological Defect Array in Nematic Liquid Crystal

YaZi Wang^1*, ieh-Wen Tsung¹

¹電子物理, 國立交通大學, 新竹市, Taiwan

* Presenter:YaZi Wang, email:yatsi841203.ep08g@nctu.edu.tw

Large array of topological defects in nematic liquid crystal (NLC) looks hazy, and thus can be applied as smart windows. The haze is a mixture of three optical effects, diffraction, scattering of light, and lensing effects. The diffraction and lensing effects are significant when the defects are periodically arranged. Sometimes the sharp glitter due to the diffraction and the split multiple image due to lensing may lead to uncomfortable visual experiences. The scatter generates the soft, milky feature which is friendly to the viewer. Therefore, creating a large amount of defects that renders the milky haze is an important issue for the smart windows. In this research, large, dense, messy topological defect network is generated in NLC test cell. The director field and diffraction pattern are analyzed carefully. Additional to the traditional haze measurement, we developed new experiment and analysis methods to distinguish the glitter of diffraction and milky texture of scattering. Our new device may lead to smart windows with better visual experiences. In addition, topological defect arrays have innovative applications, such as optical vortex generation and phase gratings. It can be used for dynamic beam steering, which is essential for holography.

Keywords: topological defect, nematic liquid crystal, microlens array, phase grating