Unusual photoanisotropic alignment in amorphous azobenzene polymers

It is well known that irradiation of azobenzene polymer films between 490 and 530 nm results in alignment of molecules perpendicular to the polarization of the incident beam. I have recently found that irradiation of amorphous azobenzene polymers with linearly polarized light at wavelengths between 560 and 630 nm, where the absorption is minimal, results in a possible uniaxial hedgehog arrangement of the molecules. Experiments performed with a dye laser, which can be tuned continuously between 560 and 630 nm, are described. Not only azobenzene but also another photosensitive molecule, bacteriorhodopsin, seems to exhibit this behavior. Irradiation of an amorphous azobenzene polymer between 560 and 630 nm between crossed polarizers produces this remarkable pattern.