Polarised light induced birefringence in azo dye doped polymer: a new model and polarised holographic experiments

The photoinduced birefringence of azo dye DMNPAA (2,5-dimelthyl-4-(p-nitrophenylazo)anisole) in PVK (Poly(N-vinylcarbazole)) thin film is reported. A two-layer model of the film is proposed to take into account the different results obtained in photoinduced birefringence experiments. According to this model, the sample exhibits intrinsic birefringence but the absorbed light can induce orientation of the optically active molecules contained in the first layer of the film, lending to photoinduced birefringence. Holographic experiments have been carried out in this media with recording at 514 nm and readout at 633 nm. Diffraction efficiency versus polarisation shows that these polymers can record polarisation states as well as intensity patterns.