ABSTRACT
We show for what is believed to be the first time that it is possible to generate 10,000 rapid write, read, and erase cycles optically in an azobenzene sidechain liquid-crystalline polyester. We do this by exposing the film alternately to visible light from an argon laser at 488 nm and ultraviolet light from a krypton laser at 351 nm. The efficiency of the system shows several exponential decays, presumably associated with the azobenzene chromophores' aligning out of the plane of the film and the lifetime of the cis state of the azobenzene. A local temperature increase may also play a role. However, there is enough contrast even after 10,000 cycles to permit a clear distinction between the maximum and the minimum anisotropy. As the anisotropy is stable between erasures, this method could have immediate applications for optical storage.
ABSTRACT
Reversible photoinduced anisotropy in a series of liquid-crystalline azobenzene side-chain polyesters is investigated as a function of intensity of the write beam and the sample temperature. Measurements reveal that the erasing takes place at a temperature much higher than the glass transition temperature. Induced anisotropy can be erased by heating the polyesters to approximately 80 °C.
