LCP research on the back cover of Advanced Optical Materials

Back Cover Advanced Optical materials (march 2018), Inge Nys, Ke Chen, Jeroen Beeckman and Kristiaan Neyts  (large view)

Back Cover Advanced Optical materials (march 2018), Inge Nys, Ke Chen, Jeroen Beeckman and Kristiaan Neyts

(03-04-2018) Inge Nys, Ke Chen, Jeroen Beeckman and Kristiaan Neyts of the research group Liquid Crystals and Photonics got featured on the back cover of the latest 'Advanced Optical Materials' magazine, vol. 6,nr.6, March 19, 2018!

Cover picture

They developed a liquid crystal photo-alignment method in which the polar and azimuthal anchoring are determined by the intensity and the polarization of the UV illumination. Patterned UV illumination of the two-component alignment layer yields surfaces with periodic stripes of planar and homeotropic anchoring. The interplay between the patterned surface anchoring and the chirality of the liquid crystal leads to the formation of new chiral superstructures. Website Advanced Optical Materials : https://onlinelibrary.wiley.com/doi/abs/10.1002/adom.201870025

 

Abstract: https://onlinelibrary.wiley.com/doi/abs/10.1002/adom.201701163

 

Layman's abstract

Liquid crystals are soft, liquid materials in which long organic molecules prefer to align parallel to their neighbors. This type of material can organize itself into complex structures and can be responsive to external stimuli such as heat or electric fields. Nowadays liquid crystals are widely used in displays (known as LCDs or liquid crystal displays) but they can also be used in other applications such as tunable lenses or smart windows. To explore their full potential and to develop functional devices it is essential to control the alignment of the liquid crystal at the solid surfaces.

 

In this study, a new method is developed to define the orientation of the liquid crystal at the interface with a solid surface. A two-component photo-sensitive material on the surface is illuminated by ultra-violet (UV) light with a given intensity and polarization. Illumination with an inhomogeneous UV beam (for example by interference between two coherent laser beams) makes it possible to define regions with alignment parallel or perpendicular to the substrate. In the past such an inhomogeneous alignment was only possible by using complicated techniques involving a combination of multiple layers. In this work a two-component material is deposited as a single layer and a linear pattern of UV illumination yields a surface with stripes of parallel and perpendicular alignment. With this alignment at the surface, complex structures in chiral liquid crystals can be stabilized. This offers interesting possibilities for the realization of diffraction gratings and for the stabilization of uniform lying helix structures that can be used in lasing and display applications. The interplay between the patterned surface anchoring and the chirality of the material has been verified by comparing numerical simulation of the liquid crystal orientation and optical transmission with experimental results.

 

Further optimization of this technique, having the advantage of simplicity and versatility, can lead to full control of the liquid crystal orientation on a micrometer scale. This can open up new possibilities in different fields, such as in-plane lasing, flat optics and new display modes.