Photo-induced control of bubble domains in chiral–nematic liquid crystal by a violet laser beam

Abstract

The stable bubble domains generated by mixing 10% of chiral molecules into an azobenzene liquid crystal (LC)-doped nematic host can be optically controlled by a violet laser beam (415 nm). The photon-induced reversible trans–cis photo-isomerisation of azobenzene changes the helical twisting power (HTP) of LC mixtures in which the HTP of cis-azobenzene LC is lower than trans-azobenzene LC. Under the irradiation of an optical field (>20 mW cm^− 2), the helical pitch distance, which is inverted proportional to the HTP, increases and the bubble domains disappear. Immediate obstruction of laser light irradiation initiates cholesteric nucleation, merging of domains and the subsequent generation of stably dispersed bubble domains.

Keywords:

• liquid crystal
• chiral–nematic
• photo-induced control
• bubble domains

Acknowledgements

This work was supported by the National Science Council, Taiwan, under project No. 97-2221-E-260-003 and the Taichung Veterans General Hospital (TCVGH-NCNU 987907). The authors thank John R. Waldeisen for technical discussion and preparation of the paper, and the Kou Ryou Enterprise Corp., Taiwan, for offering spacers.