  Peculiar light-matter interactions can break the rule that a single beam
polarization can address only two states in an optical memory device.
Multistate storage of a single beam polarization is achieved using self-induced
surface diffraction gratings in a photo-active polymer material. The grating
orientation follows the incident light beam polarization direction. The
permanent self-induced surface relief grating can be readout in real time using
the same laser beam.

Optics