Transmitted Ellipsometry Method for Extracting Physical Parameters of TN/VA/Inverse-TN Liquid Crystal Cells

Abstract

A transmitted ellipsometry method is proposed for extracting the ellipsometric parameters (Ψ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pp</i> , Ψ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ps</i> , Ψ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sp</i> , Δ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pp</i> , Δ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ps</i> and Δ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sp</i> ) of twisted nematic (TN), vertical alignment (VA), and inverse-TN (ITN) liquid crystal (LC) cells from the output Stokes parameters corresponding to five input polarized lights. The validity of the proposed approach is confirmed by comparing the experimental values of Ψ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pp</i> , Ψ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ps</i> , Ψ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sp</i> , Δ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pp</i> , Δ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ps</i> , and Δ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sp</i> with the simulated values obtained via a Genetic Algorithm curve-fitting approach. In experiments, the cell gap, pretilt angle, twist angle, and rubbing direction of TNLC and the cell gap, pretilt angle, and rubbing direction of VALC are extracted successfully. The sensitivity analysis results reveal that the ellipsometric parameters of the TNLC cell are sensitive to the cell gap, pretilt angle, twist angle and rubbing direction. However, those of the VALC and ITNLC cells are sensitive only to the cell gap, pretilt angle and rubbing direction. Overall, the results presented in this paper show that the proposed transmitted ellipsometry method provides a straightforward and accurate means of determining the ellipsometric and physical parameters of TN, VA, and inverse-TN LC cells.