Volume holographic polarization gratings have been stored in thick films of blends of a side-chain azobenzene polyester and a poly(methyl methacrylate) (PMMA) homopolymers. The azobenzene content in the blend is 0.2wt%, and the holograms are recorded by using 2ms 4mJ/cm2 488nm light pulses. The dependence of holographic storage on the recording condition has been studied. No stable gratings can be recorded in thermally quenched films. The presence of cis isomers that can be induced by blue light irradiation seems to be necessary to store stable gratings. The cis isomer content and consequently the grating efficiency can be changed by blue and red light irradiation. By choosing appropriate conditions stable and rewritable polarization gratings have been recorded. Up to 20 gratings with diffraction efficiency values higher than 5×10−5 have been multiplexed.
- Photo-induced anisotropy
- Volume holography