Characterisation of POLICRYPS structures assembled through a two-step process

Abstract

We describe optical diffraction properties of polymer liquid-crystal polymer slices (POLICRYPS) assembled through a two-step procedure. At first, a scaffold of periodic polymer slices is fabricated by a direct laser writing method based on two-photon polymerisation. Then the channels between the slices are filled with liquid crystal, and the assembly is incorporated between two ITO-coated glass plates. In contrast to the ‘classical’ POLICRYPS that are fabricated on the basis of a phase separation process and that exhibit spontaneous liquid crystal alignment in the direction perpendicular to the polymer slices (homeotropic alignment), the structures fabricated by the two-step method exhibit spontaneous liquid crystal alignment in a direction parallel to the polymer slices (planar alignment). Consequently, their optical diffraction properties as a function of the polarisation direction of the optical radiation exhibit orthogonal behaviour with respect to the classical structures. The threshold external field for electro-optic switching is in the range of 0.5 V/μm. The associated electro-optic switching times are in the range of milliseconds.

Keywords:

• polymer-liquid crystal microstructures
• two-photon polymerisation
• optical diffraction
• switchable gratings

Funding

We acknowledge financial support in the framework of the National Key Basic Research Program of China [2010CB934101], the National Natural Science Foundation of China [61205035], International S&T cooperation program of China [2011DFA52870], the 111 Project [B07013], and Slovenian research program P1–0912–‘Light and Matter’.