title: Dual-grating formation through photorefractivity and photoisomerization in azo-dye-doped polymers.
abstract: Gratings formed by photorefractive and photoisomerization processes in an azo-dye-doped polymer, poly(vinyl carbazole):trinitrofluorenone/Disperse Red I, are investigated by polarization- and field-dependent four-wave mixing experiments. High diffraction efficiencies and long storage times are observed for the photorefractive gratings. Both types of grating are erasable, and we can select them by choosing the polarization of the reading beam. The effect of photoisomerization on photorefractivity is discussed. Our results indicate that azo-dye-doped polymers are promising candidates for reversible optical storage applications.