Methyl-red Doped Liquid Crystal Research Articles

High diffraction efficiency in permanent optical memories based on Methyl Red doped liquid crystal

This paper proposes a method for enhancing diffraction efficiency in an existing grating by re-illumination of the sample with a secondary pump beam. Though this single-armed pump beam is typically used to erase the grating, in specific conditions, as in our case for Methyl Red doped liquid crystal, it increases the diffraction efficiency. Describing physical background of this enhancement based on the molecules reorientation, high diffraction efficiencies (around 11.5 %) are reported which are not obtainable during the grating formation, even after long exposure times. Concerning the permanency of the obtained efficiency, this system may find various applications in read-only optical data storage devices.

Anchoring of 4-Dimethyl-amino Substituted Azobenzene Dyes Doped Liquid Crystals on Substrates

We study the anchoring of 4-dimethyl-amino substituted azobenzene dyes doped liquid crystals and the formation of permanent gratings in the nematic liquid crystal 5CB. The increase on the dipolar interaction due to trans-cis isomerization, and the resulting anchoring to the substrate, is not enough to explain the formation of permanent gratings as it is commonly believed. We demonstrate that a strong interaction of the acid group in the 4-dimethylamino-2′-carboxylic acid substituted azo (Methyl Red, MR) dye can occur with the solid substrate through hydrogen bonding intermolecular interaction leading to permanent gratings in methyl red doped liquid crystal cells.

Holographic image storage and multiple hologram storage in a planar Methyl Red-doped liquid crystal film

Holographic images are recorded and the diffraction characteristic of the hologram is investigated in a planar Methyl Red-doped liquid crystal film without an external electric field. Multiple holograms are stored in this film with no external electric field, and peristrophic multiplexing, angular multiplexing, and spatial multiplexing are demonstrated to be suited for the implementation of azo-dye doped liquid crystal films among the multiplexing techniques. The diffraction efficiency is theoretically studied for multiple storage. Optical reconstruction for peristrophic multiplexed holograms and angular multiplexed holograms is discussed, which involves the peristrophic rotation angles and the recording angles, respectively.