Inscription of local surface relief gratings with a Scanning Near-field Optical Microscope on an azo-polymer film

Ivan H Bechtold,Burkhard Stiller,Ludwig Brehmer,Elisabeth A De Oliveira

doi:10.1590/s0104-14282006000400012

Ivan H Bechtold, Burkhard Stiller + Show 2 more

Open Access

https://doi.org/10.1590/s0104-14282006000400012

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Abstract

A Scanning Near-field Optical Microscope (SNOM) was used to inscribe locally limited Surface Relief Gratings (SRGs) on pDR1M, which is an azo-polymer film. The influence of parameters such as the line scanning time and the line spacing on the amplitude and the period of the gratings is discussed. SRGs have been used to orient Liquid Crystals (LCs), where the LC alignment takes place due to the elastic distortions of the nematic medium close to the surface. In addition, the photoalignment of the azo-chromophores was also used to induce LC alignment. In this work we investigate the use of local SGRs together with the photoalignment to get a local control of the LC alignment properties. The advantage of this method is that it is reversible and the gratings can easily be erased.

Highlights

Liquid Crystals (LCs) molecules tend to align parallel to the azo-dye groups and the anchoring energy depends on the concentration of
The presence of the azo- where the LC molecules tend to align with the longest axis benzene groups is essential and the so called trans-cis-trans along the direction of the grating channels, due to the miniphotoisomerization process make these materials good mization of the elastic distortions close to the surface
The aim of this work is the application of these surfaces to orient LCs, given the importance of having a local control of the LC alignment

Summary

Introduction

LC molecules tend to align parallel to the azo-dye groups and the anchoring energy depends on the concentration ofIn the last years many researchers have studied azoben- the chromophores in the film and on the irradiation time[12]. zene-containing films due to the possibility of technological The use of SRGs for LCs alignment has been studied[13,14], applications[1]. LC molecules tend to align parallel to the azo-dye groups and the anchoring energy depends on the concentration of. Zene-containing films due to the possibility of technological The use of SRGs for LCs alignment has been studied[13,14], applications[1]. For these purposes, the presence of the azo- where the LC molecules tend to align with the longest axis benzene groups is essential and the so called trans-cis-trans along the direction of the grating channels, due to the mini-. The mechanisms responsible for the SRGs forma- of the splay and bend LC elastic constants

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