Dark relaxation of holographic gratings in azobenzene and chalcogenide films

Studies of transmission holographic grating (HG) relaxation (recorded with s-s, p-p, s-p, L- L, L-R laser beam polarizations) have been carried out in organic molecular azobenzene glassy films W- 50 and W-75, and in chalcogenide glassy a-As₂S₃ film. Results previously obtained with azobenzene molecular glassy K-RJ-9 films also are used for comparison. HG with the periods of 0.50, 2.0 and 8.6 μm were studied in these films. It is found that recording efficiency in the same sa mple depends on both recording polarizations and HG period. The HG stability in the course of relaxation also depends on these factors. Anticorrelation has been observed of HG recording efficiency and stability. Recording was efficient with p-p or L-R polarizations at 2.0 μm HG period whereas it was stable with s-s L-L polarizations at 8.6μm HG period. As a rule, HG stability was higher in the samples with higher glass transition temperature. The HG dark (relaxational) self-enhancement of HG was observed in the case of W-75 (L-R polarizations, 0.50μm; s-s polarizations, 2.0μm) and in previously studied K-RJ-9 (p-p polarizations, 8.6μm) samples. Relaxational changes in diffraction efficiency are explained in terms of post-recording mass transfer under the influence of photoinduced spatially periodic mechanical stress.