Hybrid sol-gel films for holographic applications

Films based on SiO2 and containing Disperse Red 1 (DR1), carbazole units and 2,4,7-trinitro-9-fluorenone (TNF) have been prepared by a sol-gel technique. By photoinduced birefringence and photorefractive effect, holographic gratings have been produced using 488.0 nm and 632.8 nm light, respectively. Pure polarization gratings show diffraction efficiencies higher than those obtained by light intensity modulation, Various processes concerning the DR1 molecular orientation such as angular hole burning (AHB), angular redistribution (AR), Cis molecules decay and rotational diffusion are discussed to explain the temporal behaviour of the diffraction efficiencies. A poling field was not necessary to obtain photorefractive gratings, which show Asymmetric Energy Exchange (AEE) in two-beam coupling (2BC) experinients.