Local photo-reorientation of a liquid crystal using a laser focused on an azo dye-based monolayer

The orientation adopted by molecules in an azobenzene-based self-assembled monolayer (azo-SAM) is perpendicular to the polarization of incident green light due to isomerization, aligning liquid crystal (LC) correspondingly. To study the local photo reorientation of the LC, the exciting laser is focused into a small spot on the azo-SAM, of a hybrid cell made with nematic LC sandwiched between the azo-SAM and a homeotropic surface. Under irradiation with changing polarization, a variety of interesting phenomena are observed, including winding of rings of reorientation and orientational slipping. Results vs. exciting light intensities and different rotating frequencies will be reported.