Study the twist nematic liquid crystal by photoelastic modulated ellipsometry

• Main Authors: Chun-Kai Chang, 張君愷
• Other Authors: Yu-Faye Chao
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/30956029245089999011

碩士 === 國立交通大學 === 光電工程系所 === 93 === We can measure the twist nematic liquid crystal (TN-LC) parameters, such as twist angle and phase retardation by the photoelestic modulated ellipsometry without rotating any component in the system. After adjusting the rubbing direction of TN-LC, we can measure the ellipsometric parameters psi and delta in real time. For understanding the anisotropic properties of TN-LC, we rotated TN-LC and observe the unsymmetrical phenomenon in psi and delta . By careful analyzing the model, we can judge that TN-LC contains both linear and circular anisotropic properties. We also transform the measured TN-LC parameters into its corresponding ellipsometric parameters, which consist with our ellipsometric measured values. Because of the real time measurements, we can study the dynamic phenomenon of TN-LC under applied voltage; we further derive the transmission from psi、delta , and measure the response time of TN-LC. In this study, we proved that the response time is longer in low applied voltage than it is in higher applied voltage. Finally we transform psi and delta into Stokes Parameters, and trace out its polarization state on Poincare Sphere.