  Microstructure of reflection holographic grating fabricated via a
photo-isomerization process in an absorptive azopolymer film is analyzed. A
surface relief formation takes place on the film surface even in the reflection
holographic configuration. The polarization-dependent diffraction efficiency
and the polarization analysis reveal that the polarization grating structure
inside the film strongly depends on the amount of optical absorption
experienced by the two writing beams. Theoretical analysis shows that the
reflection polarization grating, while mimicking a cholesteric liquid crystal
structure, is composed of elliptic polarizations with the ellipticity going
through a periodic modulation.
