Silica-based photorefractive sol–gel films for holography

Photorefractive gratings have been obtained with 632.8 nm writing beams in organic-inorganic SiO 2 -based films. The hybrid glass is prepared by a sol-gel technique starting from organic Si precursors and contains Disperse Red 1 (DR1), carbazole units and 2,4,7-trinitro-9-fluorenone (TNF). A photorefractive gain has been determined through an asymmetric energy exchange by two-beam coupling (2BC) measurements. Polarization-sensitive gratings have been obtained at 488 nm through birefringence induced by photoisomerization. The birefringence gratings have been characterized at different polarization configurations. Pure polarization holographic gratings (sp, rl) show diffraction efficiencies higher than those obtained by ss or pp writing beams.