  Thin films of azopolymer-nanoparticles hybrid materials were fabricated with
poly[1-[4-(3-carboxy-4-hydroxyphenylazo) benzenesulfonamido]-1,2-ethanediyl]
(PAZO) and different concentrations of Ag and AgAu nanoparticles (NPs). By
illuminating the films with polarized interference patterns, surface relief
gratings (SRGs) were recorded. It was found that for some concentrations of NPs
their modulations and diffraction efficiency were higher than the obtained for
PAZO films without NPs. The effect was mainly explained by the increase of the
free volume available for the photoisomerization for certain concentrations of
NPs. The dependence of the diffraction efficiency on concentration was directly
related to changes in modulation depth. When doping with NPs, the maximum
efficiency increases more than two times the efficiency without NPs.
