Holographic recording of surface relief gratings in tolyle-based azobenzene oligomers

Holographic recording of surface relief gratings (SRG) in tolyle-based azobenzene oligomer films have been carried out at 514.5 nm. It was experimentally studied by spectroscopic and AFM methods. The maximum surface modulation amplitude was 35 nm. SRG formation is explained by the mean-field model and by the photodegradation of chromophores enabling the directional mass transport as the result of trans-cis transformations. The conclusion is made that SRG are stable but the diffraction efficiency (DE) changes are due to the complementary decaying amplitude-phase gratings. Strong polarization dependences of transmitted and reflected DE are found. They are explained by the diffraction anisotropy of gratings and by the photoinduced anisotropy of the recording medium. Different more efficient but less stable refractive index grating recording at 632.8 nm in the same samples is performed and studied as well.