Local Three-Dimensional Characterization of a Micro-Patterned Liquid Crystalline Cell by Confocal Raman Microscopy

Abstract

We present an experimental study on the local liquid crystalline alignment in a dye-doped nematic cell with an optically micropatterned command surface. The experiments have been carried out on cells filled with pentyl-cyanobiphenyl (5CB) doped with azo dyes with a wall coated with polyvinylcinnamate-fluorinated (PVCN-F) acting as command surface. The microstructures have been produced trough an anisotropic light-induced adsorption of the azo dyes on the command surface and the subsequent reorientation of the nematic axis at the interface and its propagation inside the cell has been characterized by confocal polarized micro Raman spectroscopy. Both lateral and axial profiles of nematic director and order parameter have been measured providing a 3D visualization of the microstructures. Particular attention has been given to the solid-liquid crystal interactions and their influences on the bulk liquid crystalline order.

Keywords:

• confocal polarized Raman spectroscopy
• 3D imaging
• azo dyes
• liquid crystals

Acknowledgments

We are grateful to Prof. O. Francescangeli and Dr. L. Lucchetti for providing us the know-how and the materials for the sample preparation in addition to assembled cells. We wish to thank Prof. L. Cristofolini for useful discussions. This work has been financially supported by INFM (PAIS LIMAD project) and INFM-CNR CRS Soft.