Polarization gratings in sol-gel thin films investigated through the moving grating technique

Intensity and pure polarization holographic gratings in silica-based sol-gel thin films, containing carbazole group and Disperse Red 1, are obtained by photoisomerization at 488 nm and are investigated by means of the moving grating technique (MGT). General equations relating the modulated MGT signal to amplitudes and phase shifts of the index and absorption gratings are derived for thin films in the case of different polarization configurations. It is shown that the technique, commonly used to characterize photorefractive gratings, is a powerful tool to investigate the orientation mechanisms responsible for the holographic polarization gratings formation.